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  • 1
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    [Editors' Choice] Fluorine frolicking with eight friends (2017)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publikationsdatum: 2017-02-10
    Beschreibung: Author: Jake Yeston
    Schlagwort(e): Inorganic Chemistry
    Print ISSN: 0036-8075
    Digitale ISSN: 1095-9203
    Thema: Biologie , Chemie und Pharmazie , Geologie und Paläontologie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
    Publiziert von American Association for the Advancement of Science (AAAS)
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  • 2
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    [This Week in Science] A salty route to an all-nitrogen ring (2017)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publikationsdatum: 2017-01-27
    Beschreibung: Author: Jake Yeston
    Schlagwort(e): Inorganic Chemistry
    Print ISSN: 0036-8075
    Digitale ISSN: 1095-9203
    Thema: Biologie , Chemie und Pharmazie , Geologie und Paläontologie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
    Publiziert von American Association for the Advancement of Science (AAAS)
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  • 3
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    [Perspective] Polynitrogen chemistry enters the ring (2017)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publikationsdatum: 2017-01-27
    Beschreibung: Polynitrogens have the potential for ultrahigh-performing explosives or propellants because singly or doubly bonded polynitrogens can decompose to triply bonded dinitrogen (N2) with an extraordinarily large energy release. The large energy content and relatively low activation energy toward decomposition makes the synthesis of a stable polynitrogen allotrope an extraordinary challenge. Many elements exist in different forms (allotropes)—for example, carbon can exist as graphite, diamond, buckyballs, or graphene. However, no stable neutral allotropes are known for nitrogen, and only two stable homonuclear polynitrogen ions had been isolated until now—namely, the N3− anion (1) and the N5+ cation (2). On page 374 of this issue, Zhang et al. (3) report the synthesis and characterization of the first stable salt of the cyclo-N5− anion, only the third stable homonuclear polynitrogen ion ever isolated. Author: Karl O. Christe
    Schlagwort(e): Inorganic Chemistry
    Print ISSN: 0036-8075
    Digitale ISSN: 1095-9203
    Thema: Biologie , Chemie und Pharmazie , Geologie und Paläontologie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
    Publiziert von American Association for the Advancement of Science (AAAS)
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  • 4
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    [Editors' Choice] A pair of tablemates for aromatic benzene (2016)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publikationsdatum: 2016-09-09
    Beschreibung: Author: Jake Yeston
    Schlagwort(e): Inorganic Chemistry
    Print ISSN: 0036-8075
    Digitale ISSN: 1095-9203
    Thema: Biologie , Chemie und Pharmazie , Geologie und Paläontologie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
    Publiziert von American Association for the Advancement of Science (AAAS)
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  • 5
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    [This Week in Science] Coordinated scission of N–H or O–H bonds (2016)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publikationsdatum: 2016-11-11
    Beschreibung: Author: Jake Yeston
    Schlagwort(e): Inorganic Chemistry
    Print ISSN: 0036-8075
    Digitale ISSN: 1095-9203
    Thema: Biologie , Chemie und Pharmazie , Geologie und Paläontologie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
    Publiziert von American Association for the Advancement of Science (AAAS)
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  • 6
    Digitale Medien
    Digitale Medien
    Novel one-pot polymer syntheses based on dithiols obtained from a five-membered cyclic dithiocarbonate and diamines (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 1909-1915 
    Details
    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Novel one-pot syntheses of sulfur-containing polymers from a five-membered cyclic dithiocarbonate (5-phenoxymethyl-1,3-oxathiolane-2-thione (1)) and diamines were examined. Polydisulfides with M̄n 5400 ∼ 15800 were obtained in the oxidation polymerization of dithiols 2, which were obtained in situ by the reactions of 1 and diamines. When 1,12-dodecanediamine was employed, a polydisulfide with relatively high M̄n was obtained, while in the case of m-xylylenediamine, the polymerization was accompanied by intermolecular cyclization to give a polydisulfide with low M̄n. Polythiourethanes with M̄n 6500 ∼ 17200 were obtained in the polyaddition of 2 with 4,4′-methylenebis(phenyl isocyanate). The yields and M̄n values increase with increasing methylene chain length of 2. Polythioethers with M̄n 2600 ∼ 19900 were obtained by the polycondensations of 2 with α,α′-dibromo-p-xylene. The glass transition temperature (Tg) of the polymer decreases with increasing methylene chain length in the main chain.
    Zusätzliches Material: 3 Tab.
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  • 7
    Digitale Medien
    Digitale Medien
    Synthesis of novel oligomeric peroxides via condensation of dihydroperoxides with aromatic diols (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 1927-1933 
    Details
    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Novel oligoperoxides α-hydro-ω-hydroperoxyoligo(dioxydimethylmethylene-1,4-phenylene-dimethylmethylene) (BPB) (Tm = 143°C, Td = 176°C), α-hydro-ω-hydroxyoligo(dioxydimethylmethylene-1,4-phenylenedimethylmethylenedioxydimethylmethyleneethy lenedimethylmethylene) (EPB) (Tm = 100°C, Td = 175°C) and α-hydro-ω-hydroperoxyoligo(dimethylmethylene-2,6-naphthylenedimethylmethylene (NPN) (Tm = 137°C, Td = 177°C)), the products of condensation of tertiary diols with tertiary dihydroperoxides, were obtained. The structure of the oligoperoxides was confirmed by spectroscopic methods (IR, NMR). Their thermal properties were studied by differential scanning calorimetry (DSC), and the mechanism of the thermal decomposition of the oligomeric peroxides was proposed basing on the GC-MS analysis of the degradation products.
    Zusätzliches Material: 4 Ill.
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  • 8
    Digitale Medien
    Digitale Medien
    Liquid crystalline thermosets from triaromatic azomethine group containing diepoxides and 4,4′-methylenedianiline (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 1935-1938 
    Details
    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Five triaromatic azomethine-linked diepoxides have been cured by reaction with 4,4′-methyl-enedianiline (MDA) in a molar ratio epoxide/amine of 1:1 and 2:1. The influence of the structure of monomers, of the molar ratio epoxide/amine, and of the curing conditions on the formation of liquid crystalline networks was studied. Initially a decrease of the clearing temperature was caused by mixing with the nonmesogenic diamine. The clearing point of the mixture increased with conversion, and thermosets with a liquid crystal order of the monomers were obtained from the 2:1 combinations. Curing occurs in two stages as revealed by DSC: first epoxy/amine reaction occurs, and at higher temperature homopolymerisation of residual oxirane takes place. This is due to non-homogeneous melting of the diepoxides in dynamic curing.
    Zusätzliches Material: 3 Ill.
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  • 9
    Digitale Medien
    Digitale Medien
    Vinylic polymerization of bicyclo[2.2.1]hept-2-ene by Co(II)-catalysis (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 1951-1956 
    Details
    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The vinylic polymerization of bicyclo[2.2.1]hept-2-ene (norbornene) with Co(II) compounds, such as Co(II) stearate, substituted bis(1,3-diketo)cobalt(II), Co(dppe)Cl2, and the metallocene [η5-(C5Me5)Co-η2-Cl]2, in chlorobenzene activated with methylaluminoxane (MAO) is reported. MAO* synthesized by the hydrolysis of trimethylaluminium in chlorobenzene instead of toluene increases the catalytical activity strongly, and a turn over of 2.7 tons of poly(2,3-bicyclo[2.2.1]hept-2-ene) per mol cobalt per hour was achieved. The polymers obtained are amorphous (WAXS). They show weight-average molecular weights up to M̄w = 1.5 · 106 and are soluble in chlorobenzene, 1,2-dichlorobenzene, cyclohexane, and decahydronaphthalene.
    Zusätzliches Material: 1 Ill.
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  • 10
    Digitale Medien
    Digitale Medien
    Influence of batch reaction conditions on norbornene/ethylene copolymers made using C2v- and Cs-symmetric metallocene/MAO catalysts (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 1939-1942 
    Details
    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The norbornene/ethylene copolymerization was studied using C2v- and Cs-symmetric metallocene catalysts in the presence of methylaluminoxane as a cocatalyst. The batch reactions were carried out at four different temperatures copolymerizing a constant amount of ethylene with the appropriate amount of norbornene. The activity decreases for the Cp2ZrCl2 catalyst and increases to a constant level for the [Ph2C(Flu)(Cp)]ZrCl2 catalyst when the norbornene/ethylene ratio in the reaction increased. The highest activities and the highest norbornene contents in the copolymers were achieved using the [Ph2C(Flu)(Cp)]ZrCl2. The microstructure of the copolymer determined with 13C NMR was observed to depend on catalyst, temperature and monomer ratio. Cp2ZrCl2 produces more norbornene blocks as a function of norbornene content in the copolymer and longer norbornene sequences than [Ph2C(Flu)(Cp)]ZrCl2. The correlation between the increasing norbornene content in the copolymer and the increasing glass transition temperature is more obvious for [Ph2C(Flu)(Cp)]ZrCl2.
    Zusätzliches Material: 3 Ill.
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  • 11
    Digitale Medien
    Digitale Medien
    New azo-dye containing side group copolymethacrylates (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 1943-1949 
    Details
    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: A new type of side group copolymethacrylates was synthesized, characterized and tested with respect to its behavior on irradiation with an Ar+-laser beam. The side groups consist of methylene spacer units with different length and of three-ring mesogens with an ester group between the first and the second aromatic ring and on the other hand of two-ring mesogens with an azo-structure between the aromatic rings, respectively. The azochromophoric structure contains different substituents in the terminal aromatic ring. The homopolymers of the azo-dye containing monomers do not display liquid crystalline (lc) mesophases, but the three-ring mesogens induce lc-phases in opposition to the equimolaric copolymers with two-ring ester group mesogens. The lc phases are important for the stability of the recorded change of birefringence (photorecording process) which is influenced by irradiation of the polymers.
    Zusätzliches Material: 4 Ill.
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  • 12
    Digitale Medien
    Digitale Medien
    Miscibility of functionalized polyolefins with polyamide-6 as detected by solid-state NMR (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 1957-1963 
    Details
    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Solid-state NMR was used to investigate the miscibility of LLDPE/polyamide-6 blends. Two different blends B1 and B2, obtained with LLDPE only and with LLDPE functionalized with diethyl succinate, respectively, as well as their individual components, were characterized by means of 13C selective techniques. Measurement of 1H spin-lattice relaxation times in both laboratory and rotating frames allowed the miscibility at a molecular level to be investigated for both blends: in B1 the domains of the different components are on average larger than 100-200 Å, whereas in B2, where two different fractions could be separated on the basis of their solubility in heptane, the average linear dimensions of the insoluble fraction are between 20 and 200 Å.
    Zusätzliches Material: 6 Ill.
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  • 13
    Digitale Medien
    Digitale Medien
    Tetrahexylsexithiophene: crystal structure and molecular mechanics calculations (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 1973-1979 
    Details
    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The synthesis, crystal structure and detatiled molecular mechanics calculations, including crystal packing interactions, of tetrahexylsubstituted sexithienylene are presented. Unexpectedly the molecule, which arranges in the P-1 space group, displays no herringbone arrangement, thienylenic rings are far from coplanarity and the alkylic side chains present different conformations. Molecular mechanics fully accounts for these findings. From crystal packing computations it is derived that different arrangements are unable to lower the packing energy, due to the closeness of two alkyl chains on the same side of the thienylenic backbone, which prevents interspersion of non-parallel molecules.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 14
    Digitale Medien
    Digitale Medien
    Copolymerization of ethene with 1-hexene or 1-hexadecene over ethylene, dimethylsilylene and 1,4-butanediylsilylene bridged bis(indenyl) and bis(tetrahydroindenyl)zirconium dichlorides (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 1965-1972 
    Details
    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Ethene was copolymerized with 1-hexene and 1-hexadecene over five different homogeneous methylaluminoxane (MAO) activated racemic ansa-metallocene catalysts in order to study both the influence of the ligand (indenyl and tetrahydroindenyl) and the influence of the interannular bridge (ethylene, dimethylsilylene and 1,4-butanediylsilylene) on the copolymerization behaviour. Hydrogenation of the indenyl ligands was found to decrease comonomer content and molar mass of the copolymers. A similar tendency was observed for the ethylene bridge compared to the silylene bridges. The reasons for this behaviour are discussed and related to structural differences of the catalyst precursors. In addition a segregation fractionation technique was applied to study the chemical composition distribution (CCD) of the produced copolymers. Batchwise feed of comonomer resulted in a broad CCD. More homogeneous copolymers could be produced using partly continuous feed of comonomer.
    Zusätzliches Material: 6 Ill.
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  • 15
    Digitale Medien
    Digitale Medien
    4-[Diphenyl(trimethylsilyl)methyl]benzophenone as initiator in the photopolymerization of methyl methacrylate and styrenePartly presented at the 4th Greek Polymer Chemical Congress, Patras, November 1997, Greece. (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 1981-1987 
    Details
    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The polymerization of methyl methacrylate (MMA) and styrene (St) has been studied using 4-[diphenyl(trimethylsilyl)methyl]benzophenone 1 as photoinitiator. The polymerization follows a free radical mechanism; the polymerization rate increases linearly with the monomer concentration and was found to be proportional to the 0.33 and 1.40 power of the photoinitiator and the monomer (MMA) concentration, respectively. The overall activation energy in the case of MMA photopolymerization was calculated to be 25.0 kJ/mol. From 1H NMR studies it is concluded that the obtained polymers contain two different trimethylsilyl moieties, one at the head and the other at the tail of the polymer chain, showing primary termination reactions even at low initiator concentrations. The p-benzoyltrityl radical 1· is incorporated into the polymer chain to a very small extent, acting as a scavenger. This is also concluded by laser flash photolysis (LFP) and ESR spectroscopy measurements. A “living” character of the polymerization was observed only at very low initiator concentrations. The triplet state (31*) of the initiator was quenched by styrene, reducing its efficiency. The rate constant kq of the quenching process of 31* was measured by LFP (kq = 3.1 · 109 M-1 · S-1). The triplet state and the photodissociation efficiency of the initiator is unaffected by MMA at various concentrations.
    Zusätzliches Material: 8 Ill.
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  • 16
    Digitale Medien
    Digitale Medien
    Reactivity ratios and sequence determination of acrylonitrile/hexyl methacrylate copolymers by one and two dimensional NMR spectroscopy (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2005-2015 
    Details
    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Acrylonitrile/hexyl methacrylate copolymers of different monomer composition were prepared by photopolymerization using uranyl ions as photosensitizer. The copolymer composition data were used to calculate the comonomer reactivity ratios according to the Kelen Tüdős (KT) and the error-in-variables model (EVM) method. The reactivity ratios obtained from the EVM method are rA = 0.14 ± 0.03 and rH = 1.32 ± 0.17. The microstructure was obtained in terms of distribution of A and H centred triad sequences from 13C{1H} NMR spectra of the copolymers. The copolymerization mechanism was determined by using Cheng's methodology. It was found that the Markov second order model gave a good fit to the experimental data. The complex and overlapping proton and carbon signals of A/H copolymers were assigned to various compositional and configurational sequences with the help of inverse HETCOR experiments.
    Zusätzliches Material: 10 Ill.
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  • 17
    Digitale Medien
    Digitale Medien
    The effect of temperature on the polymerization of propene with dimethylsilylbis(1-indenyl)zirconium dichloride/methylaluminoxane and dimethylsilylbis(2-methyl-1-indenyl)zirconium dichloride/methylaluminoxane. Modeling of kinetics (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 1989-2004 
    Details
    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Propene polymerizations were performed using the two ansa-zirconocene catalyst systems dimethylsilylbis(1-indenyl)zirconium dichloride/methylaluminoxane and dimethylsilylbis(2-methyl-1-indenyl)zirconium dichloride/methylaluminoxane. The polymerization rate was observed by continuously monitoring the monomer consumption. Reaction rate profiles were obtained in the temperature range from 40°C to 130°C at pressures between 1 and 2.5 bar and catalyst concentrations from 4.6 · 10-6 M to 4.2 · 10-5 M. Isotacticity, as measured by NMR, melting point and molecular weight decreases markedly at higher temperatures. Small amounts of 1,3-inserted monomer (〈1 mol-%) was observed at polymerization temperatures above 80°C. No 2,1-inserted monomer was detected. A kinetic model was developed that describes the polymerization rate for Me2Si(Ind)2ZrCl2 as the catalyst over the entire observed temperature range, and the polymerization rate for Me2Si(2-Me-Ind)2ZrCl2 in a limited temperature range. The model includes an activation reaction, latent sites that may revert to active sites and a permanent deactivation that is second order with respect to the active sites. The activation energy for the propagation reaction was found to be 37 kJ/mol for Me2Si(Ind)2ZrCl2 and 32 kJ/mol for Me2Si(2-Me-Ind)2ZrCl2/MAO. Several kinetic models are compared and discussed.
    Zusätzliches Material: 18 Ill.
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  • 18
    Digitale Medien
    Digitale Medien
    Preparation of poly(lactic acid)-grafted amylose through the trimethylsilyl protection method and its biodegradation (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2017-2022 
    Details
    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Biodegradable poly(lactic acid)-grafted amylose was synthesized using a trimethylsilyl (TMS) protection method. Tetrahydrofuran soluble, mostly trimethylsilyl protected amylose was prepared and reacted with potassium tert-butoxide to give the corresponding alkoxide. Poly(lactic acid)-grafted amyloses were obtained by ring-opening anionic polymerization of lactide using the polymeric alkoxides as initiators and subsequent removal of the TMS groups. The obtained graft copolymers show biodegradability and a microphase-separated morphology.
    Zusätzliches Material: 3 Ill.
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  • 19
    Digitale Medien
    Digitale Medien
    On the multiple melting behavior of polymorphic syndiotactic polystyrene and its behavior in a miscible state (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2041-2049 
    Details
    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Differential scanning calorimetry (DSC) and X-ray diffraction analysis were performed to study the multiple melting behavior and crystal forms of neat syndiotactic polystyrene (s-PS) in comparison with its miscible blends with amorphous atactic polystyrene (a-PS) or poly(2,6-dimethyl-p-phenylene oxide) (PPO). For neat s-PS annealed at 242 to 250°C, three melting peaks of changing intensity were observed (labeled I, II, and III from low to high temperature), while if annealed at high temperatures (254°C or higher) only two melting peaks were left. The missing peak was determined to be Peak-III for s-PS annealed at high temperatures. For the s-PS/a-PS or s-PS/PPO blends, two melting peaks were observed, and the missing peak is Peak-II. The missing Peak-II in the blend systems is attributed to the β-modification. Apparently, the condition of s-PS being compatible with a-PS or PPO is unfavorable for generating the β-modification upon melt crystallization. This study also showed that Peak-I is associated with the β-modification. Peak-III may be associated with the less stable β′ form, which can be transformed to the β form upon annealing at high temperatures. For the s-PS/a-PS or s-PS/PPO blends upon annealing at higher temperatures, Peak-III quickly decreases, leaving only a single melting peak (Peak-I) for the blends. The phenomenon of the decrease of Peak-III crystals in the blend is similar to that for neat s-PS annealed at high temperatures.
    Zusätzliches Material: 7 Ill.
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  • 20
    Digitale Medien
    Digitale Medien
    Rheological behavior of cured acrylate-terminated unsaturated copolyesters (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2029-2039 
    Details
    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The viscoelastic properties of cured acrylate-terminated copolyesters were studied by means of dynamic mechanical analysis. The influence of terminal double bonds, as well as of the cis-trans configuration and distribution along the main chain, on the transition temperatures and rheological properties of the cured polyesters are presented. The presence of double bonds at both chain ends allows the formation of a regular network by crosslinking copolymerization with styrene. The present investigation was carried out on three series of acrylate-terminated copolyesters: poly[(tetramethylene maleate)-co-(tetramethylene phthalate)] (BMPA), poly[(tetramethylene fumarate)-co-(tetramethylene phthalate)] (BFPA) and poly[(tetramethylene phthalate)-co-(tetramethylene succinate)] (BPSA). The results of the mechanical spectrometric analysis are presented as master curves by applying the time-temperature superposition principle. The WLF parameters of the cured unsaturated polyesters were determined above the glass transition temperatures. The glass transition temperatures shift to higher temperatures with increasing degree of crosslinking. The equilibrium shear storage modulus plateau changes as a consequence of the different configuration of the double bonds and the degree of crosslinking. The degree of crosslinking, nc, determined from the equilibrium shear modulus G′e, was higher than those determined from equilibrium swelling measurements, which is apparently connected with the contribution of physical entanglements.
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  • 21
    Digitale Medien
    Digitale Medien
    Preparation of poly(methyl methacrylate) microspheres modified with amino acid moieties (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2023-2028 
    Details
    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Poly(methyl methacrylate) microspheres [poly(SerMA-co-MMA), poly(AlaMAm-co-MMA), poly(AlaEMA-co-MMA), and poly(AlaMAm/AlaEMA-co-MMA)] modified with O-methacryloyl-L-serine (SerMA), N-methacryloyl-L-alanine (AlaMAm) and L-alanine 2-methacryloyloxyethyl ester (AlaEMA) were prepared by the emulsifier-free emulsion copolymerization of methyl methacrylate (MMA) with SerMA, AlaMAm and AlaEMA, respectively, initiated with 2,2′-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride (ABIP). The series of polymer microspheres showed unimodal distribution of the particle size (290-800 nm) in water. From X-ray photoelectron spectroscopy it was concluded that the amino acid moieties are located on the surface of the particles in all cases. Poly(SerMA-co-MMA) showed the most effective suppression of adsorption of proteins such as albumin (Alb), γ-globulin (Glo) and fibrinogen (Fib) among the examined poly(methylmethacrylate) microspheres.
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  • 22
    Digitale Medien
    Digitale Medien
    Thermotropic liquid crystalline poly(vinyl ether)s with pendant cellobiose residues: Synthesis and mesophase structure (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2071-2077 
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    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: This study concerns the synthesis of poly(vinyl ether)s (VEs) carrying pendant cellobiose heptadecanoate (CHD) residues and their mesomorphic properties examined by DSC, polarization microscopy and X-ray diffraction. The poly(VE)s were synthesized through cationic polymerization of a CHD-substituted VE, i.e., 10-(vinyloxy)decyl-2,2′,3,3′,4′,6,6′-hepta-O-decanoyl-β-D-cellobioside. From X-ray diffraction analyses, the mesophase of the poly(VE) proved to be closely similar to that of the star-shaped triplet derivative. The mesophase is characterized by the following features; (i) it consists of discotic columns built up by a regular stacking of the pendant CHD residues, (ii) each polymer main chain is presumed to have an extended conformation due to the periodic stacking of the pendant CHD moieties into a columnar structure, and (iii) each polymer molecule independently forms three discotic columns, which surround the main chain, without any intercalation of the CHD pendants originating from different polymer molecules.
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  • 23
    Digitale Medien
    Digitale Medien
    Effects of mixed surfactants on the styrene miniemulsion polymerization in the presence of an alkyl methacrylate (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2051-2061 
    Details
    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The influence of the mixed surfactants sodium dodecyl sulfate (SDS) and nonylphenol polyethoxylate with an average of 40 ethylene oxide units per molecule (NP-40) on the styrene (ST) miniemulsion polymerization in the presence of dodecyl methacrylate (DMA) and stearyl methacrylate (SMA) was investigated. Both Ostwald ripening and creaming could not be neglected for the miniemulsions stabilized by SDS/NP-40 in combination with DMA upon aging at 35°C, whereas no appreciable Ostwald ripening and creaming were detected for the SMA containing miniemulsions. For both the DMA and SMA containing polymerizations at 80°C, the rate of polymerization (Rp) decreases with increasing NP-40 concentration ([NP-40]). Incorporation of a small quantity of the extremely water-insoluble blue dye into the reaction system was applied to probe the particle nucleation loci. For the DMA containing polymerizations with [NP-40] = 0, 1.25, and 2.50 mM and the SMA polymerization with [NP-40] = 0 mM, homogeneous or micellar nucleation can not be ignored. On the other hand, the more hydrophobic SMA in combination with SDS/NP-40 effectively retards the particle nucleation occurring in the aqueous or micellar phase.
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  • 24
    Digitale Medien
    Digitale Medien
    Crystallization kinetics and melting behavior of poly(butylene adipate), poly(butylene isophthalate) and their copolymers (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2063-2070 
    Details
    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The melting behavior and the isothermal crystallization kinetics of poly(butylene adipate), poly(butylene isophthalate) and their random copolymers were investigated by means of differential scanning calorimetry. Multiple endotherms, commonly observed on the melting polyesters, were found to be influenced by crystallization temperature and composition. By applying the Hoffman-Weeks method to the isothermally crystallized samples, the equilibrium melting temperatures of the homopolymers were obtained. From calorimetric results on samples with different degree of crystallinity, the equilibrium melting enthalpy of poly(butylene isophthalate) was calculated and the presence of a crystal-amorphous interphase in copolymers was evidenced. Isothermal melt crystallization kinetics was analyzed according to the Avrami equation. As expected, the introduction of a comonomer was found to decrease the overall crystallization rate of the polymers. Values of Avrami exponent close to three were obtained for all the samples, independently of composition and crystallization temperature, in agreement with a crystallization process originating from predetermined nuclei and characterized by three-dimensional spherulitic growth. In the case of poly(butylene isophthalate), the dependence of the rate of crystallization on Tc shows a maximum at an undercooling of approximately 60°C.
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  • 25
    Digitale Medien
    Digitale Medien
    Preparation, properties and biodegradation of stereoregular copolymers of (R,S)-3-butyrolactone and 4-butyrolactone (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2079-2085 
    Details
    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Copolymers obtained from the copolymerization of (R,S)-3-butyrolactone ((R,S)-3-BL) and 4-butyrolactone (4-BL) catalyzed by isobutylaluminoxane were compared in structure and properties to copolymers having the same types of repeating units produced by Alcaligenes eutrophus when grown with an appropriate substrate or substrate or substrate mixtures. Copolymers with 4-BL contents up to 33 mol-% were prepared and characterized by 1H NMR, 13C NMR, gel permeation chromatography (GPC) and differential scanning calorimetry (DSC). The copolymers had a sequence distribution of 3-hydroxybutyrate (3-HB) and 4-hydroxybutyrate (4-HB) units which were non-random in that very few, if any, sequences of more than two successive 4-HB units were present. The 3-HB units are believed to be separated into isotactic (R) and (S) blocks, but thermal analysis by DSC showed that both the glass transition temperatures and melting temperatures decreased in a regular manner with increasing contents of 4-HB units. Number average molecular weights of the copolymers (Mn) ranged from 7000 to 15000. Biodegradation tests with a bacterial hydrolase showed that the biodegradation rates increased with increasing contents of 4-HB units, as is the case for the equivalent bacterial copolymers.
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  • 26
    Digitale Medien
    Digitale Medien
    Preparation of side-chain liquid-crystalline polymers via pyridylphenol hydrogen bonding (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2101-2105 
    Details
    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: A series of side-chain liquid-crystalline polymers via pyridyl-phenol hydrogen bonding complexation was prepared by using non-liquid-crystalline precursors, such as poly[(4-vinylpyridine)-co-(butyl acrylate)] and 4-(4′-nitrophenylazo)phenol, 4-(4′-methoxyphenylazo)phenol or 4-(phenylazo)phenol. The association by hydrogen bonding was confirmed by means of FTIR. While the hydrogen bonds are weakened, and some dissociation occurs at the isotropization temperature, complete dissociation needs much higher temperature. The hydrogen bonds re-form as the complex is cooled to room temperature. The nematic liquid crystallinity of the polymer complexes was shown by means of wide-angle X-ray diffraction (WXRD) and polarized optical microscopy (POM). The different substitution groups of azophenol give isotropization temperatures of the polymer complexes in the following sequence: —NO2 〉 —H 〉 —OCH3.
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  • 27
    Digitale Medien
    Digitale Medien
    Tailored rigid-flexible block copolymers, 4Part 3: cf. ref.3. Synthesis and properties of diblocks of poly(p-benzamide) and poly(m-benzamide) (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2087-2094 
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    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Copolymers were prepared by the condensation of rigid benzoyl-terminated poly(p-benzamide) and flexible anilino-terminated poly(m-benzamide) prepolymers. The use of two monomers of the AB type and of end-capped prepolymers resulted in the formation of diblock molecules uncontaminated by triblock or multiblock sequences. Moreover, selective extraction techniques in N,N-dimethylacetamide (DMAc) with varying amounts of LiCl resulted in the complete elimination of unreacted prepolymers, as evidenced from material balance and 1H NMR data. The above extraction technique also allowed a fractionation of the copolymers in terms of their rigid/flexible compositional distribution ratio. The molecular weight-intrinsic viscosity dependence of poly(m-benzamide) determined in a nonaggregating solvent using light scattering yielded a persistence length of 8 Å, suggesting a relatively large chain flexibility. A tailored copolymer with a fraction β of flexible residues = 0.70 was fractionated, determining the solubility, the viscosity, and the critical composition for mesophase formation in DMAc/LiCl and in 96% H2SO4 solutions. The results, in line with those previously reported for a related system, reveal that the addition of the flexible segment has a little effect on the critical concentration of poly(p-benzamide), whereas the biphasic gap is strongly reduced. Moreover, the solubility of the copolymer is substantially increased over that of the rigid homopolymer. The net result is an unexpected widening of the range of stability of the pure mesophase, with significant implications from both a fundamental and an applied standpoint.
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  • 28
    Digitale Medien
    Digitale Medien
    Synthesis and characterization of a new polymer containing an electron accepting perfluoro group (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2107-2112 
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    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Poly{oxy-4,4′-octafluorobiphenylyleneoxy-alt-[1,4-phenylenevinylene(3-trimethylsilyl-1,4-phenylene)vinylene-1,4-phenylene]} (PFSi) was synthesized and characterized to investigate its thermal, optical, electrical and xerographic properties. An LED (light emitting device) using PFSi as the light emitting layer exhibits maximum emission for blue light, but a high turn-on voltage. The origin of the low device performance was examined by investigating the photoconducting behavior. PFSi shows a high photoconductivity in the presence of electron acceptors such as 5-nitroanthranilonitrile (5NAN), and the photoconductivity of PFSi is improved by introducing charge transport materials such as triphenylamine (TPA).
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  • 29
    Digitale Medien
    Digitale Medien
    Synthesis and phase behavior of side-chain liquid crystalline polymers with pendant quinoline rings bearing either a polar or a non-polar end group (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2095-2099 
    Details
    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Four methacrylate monomers, 2a-2d, containing a quinoline ring with a NO2 or a OCH3 group at the end of the mesogen were synthesized and polymerized. The copolymers with six methylene units as spacer, 3b-3d, showed a smectic phase induced by electron donor-acceptor interactions of the side groups. The homopolymer with eleven methylene units as spacer and methoxy end group, 3f, showed a smectic phase induced by the large length of the spacer. The copolymers with eleven methylene units, 3g-3i, showed a smectic phase induced by both the electron donor-acceptor interactions of the side groups and the large length of the spacer.
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  • 30
    Digitale Medien
    Digitale Medien
    Molecular character of sharkskin phenomenon in metallocene linear low density polyethylenes (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2113-2118 
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    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The effect of molecular weight on sharkskin dynamics is systematically studied using three metallocene-catalyzed linear low density polyethylenes (mLLDPE) of different molecular weights. A new experimental method is developed to enable in-situ characterization of the time scale τ on which sharkskin forms on the extrudate. This laser scattering technique directly measures the periodic variation of the refracted light of the rough sharkskin-like extrudate surface. It is found that τ increases with molecular weight as strongly as the overall molecular chain relaxation time, τ*, determined from oscillatory shear measurements. The observed molecular weight dependence provides additional support for the recently proposed interfacial stress growth/relaxation mechanism for sharkskin formation.
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  • 31
    Digitale Medien
    Digitale Medien
    Synthesis and properties of poly(dimethyldiphenylsilylenemethylene) (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2119-2127 
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    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The novel polycarbosilane poly(dimethyldiphenylsilylenemethylene) (PDMDPSM) (2) was prepared by H2PtCl6-catalyzed ring-opening polymerization (ROP) of 1,1-dimethyl-3,3-diphenyl-1,3-disilacyclobutane (1). Polymerization in bulk at elevated temperature afforded high molecular weight PDMDPSM (Mw = 577000) with monomodal molecular weight distribution and regularly alternating SiR2/CH2 backbone structure. NMR spectroscopy revealed that a minor fraction of the monomer units is incorporated irregularly during polymerization in bulk, leading to structural units of the type —SiPh2—CH2—SiPh2— and —SiMe2—CH2—SiMe2—. The amount of regularly alternating dimethyl- and diphenylsilylenemethylene units increases when the polymerization is performed in solution at lower temperatures. PDMDPSM shows a glass transition temperature (Tg) at 50°C, which lies between the TgS of poly(methylphenylsilylenemethylene) (PMPSM) and poly(diphenylsilylenemethylene) (PDPSM), demonstrating the stiffening effect of the SiPh2 groups. Thermogravimetric analysis (TGA) evidenced nearly identical thermal stability of PDMDPSM and PMPSM.
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  • 32
    Digitale Medien
    Digitale Medien
    Supramolecular structures of poly(p-phenylenes) with oxyethylene side chains and their mixtures with lithium salts (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2129-2140 
    Details
    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: A series of poly(p-phenylenes) with linear and branched oxyethylene side chains was synthesized. Microphase separation in the solid state causes polymers with linear side chains to form supramolecular structures, which consist of main chain layers separated by an amorphous side chain matrix. If mixed with lithium salts such as lithium triflate (LiOTf) or lithium bis(trifluoromethanesulfone)imide (LiNTf), the polymers form solid solutions. The experimental data suggest that the layered structures undergo a one-dimensional swelling in the direction perpendicular to the main chain layers when blended with LiOTf and that this salt is only incorporated into the side chain matrix. The observed melting point depression in polymer-LiNTf mixtures is explained by the assumption that the salt species are incorporated both into the side chain and the main chain microphase.
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  • 33
    Digitale Medien
    Digitale Medien
    Dielectric relaxation and relationships of local molecular mobility in linear and comb-like thermotropic polymers (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2147-2152 
    Details
    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The dielectric behavior of several thermotropic linear and comb-like polymers with flexible spacers and mesogenic fragments with different structure has been studied in a frequency range from 60 Hz to 1 MHz in the bulk state (below the glass transition temperature). Two regions of dipole relaxation caused by local mobility were detected. It was shown that the relaxation parameters of the first process virtually do not change with increasing spacer length and have similar values in polymers with different structure. In the case of the second process, in increase in spacer length considerably increases the mobility of kinetic elements.
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  • 34
    Digitale Medien
    Digitale Medien
    Sequential reordering in condensation polymers, 5Parts 1-4: refs.4-7. Preparation and characterization of copolymers via transesterification of a polycaprolactonepoly(2,2-dimethyltrimethylene carbonate) blend (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2153-2164 
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    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: A blend of polycaprolactone (PCL) and poly(2,2-dimethyltrimethylene carbonate) (PDTC) containing catalytic amounts of dibutyltin dimethoxide was prepared from solution. The blend was then subjected to melt-mixing at 200°C and samples were taken after different times. According to thermal analysis data, with the increase of reaction time a gradual loss of the crystallizability of the blend components is observed, and after 70 min at 200°C the system becomes completely amorphous. 13C NMR data suggest that the loss of crystallizability of the blend is accompanied by an abrupt decrease in PCL and PDTC sequence lengths reaching after 70 min at 200°C an average length of about two repeating units each. These effects are explained by transesterification reactions between the lactone and carbonate units.
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  • 35
    Digitale Medien
    Digitale Medien
    Crystallization kinetics and morphology of poly(ferrocenyldimethylsilane) (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2141-2145 
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    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: A series of poly(ferrocenyldimethylsilanes) were prepared via anionic ring-opening polymerization. The isothermal crystallization kinetics were investigated by means of differential scanning calorimetry and analyzed in terms of the Avrami equation. The value of the Avrami exponent is approximately 3 for the majority of samples and crystallization temperatures. This suggests a three-dimensional spherulitic growth and an instantaneous nucleation mechanism. The morphology of melt-crystallized samples was studied by atomic force microscopy. Hedrites (immature spherulites) were formed at low undercoolings whereas at high levels of undercooling mature, well developed spherulites were observed with small hedritic features in their center. The melting enthalpy for a 100% crystalline polymer was estimated to be 36 J/g from differential scanning calorimetry and X-ray diffraction data obtained by using specimens with different degrees of crystallinity.
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  • 36
    Digitale Medien
    Digitale Medien
    Reactive polymers incorporating silyl enol ether groups, 3Part 2: cf. ref.1. Incorporation of α,β-bis(siloxy)vinylene units into the backbone of vinyl polymers by free-radical (co)polymerization of 2,3-bis(trialkylsiloxy)butadienes (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2173-2178 
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    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: 2,3-Bis(trimethylsiloxy)butadiene (1) and 2,3-bis(tert-butyldimethylsiloxy)butadiene (2) have been homopolymerized and copolymerized with styrene (St) and methyl methacrylate (MMA) under freeradical conditions. Comparison of initial rates and molecular weights with polymerizations conducted under identical experimental conditions on monosubstituted analogs, 2-trimethysiloxybutadiene (3) and 2-(tert-butyldimethylsiloxy)butadiene (4), demonstrated that the second substituent does not decrease the polymerizability significantly despite the additional steric hindrance introduced in the monomer. Extensive 1H and 13C NMR characterization of the polymers demonstrated that the main incorporation mode is of the 1,4-type, allowing more than 95% of the butadienyl subunit to be incorporated in the main chain as an α,β-bis(trialkylsiloxy)vinylene functional group. Monomer reactivity ratios r1 and r2 at 60°C were determined from copolymer composition curves obtained at low conversions and are compared with values obtained for other 1,2-butadienyl systems.
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  • 37
    Digitale Medien
    Digitale Medien
    Radical polyaddition-isomerization of bifunctional vinylcyclopropanes with dithiols (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2165-2172 
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    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Synthesis and radical polyaddition-isomerization of novel bifunctional vinylcyclopropane derivatives, 1,4-xylylene bis(2-isopropenyl-2-methylcyclopropanecarboxylate) (1a), ethylene bis(2-isopropenyl-2-methylcyclopropanecarboxylamide) (1b), and bis(2-isopropenyl-2-methylcyclopropanemethyl) terephthalate (1c) with dithiols were carried out. Polymers with molecular weights and polydispersities of 1100-11000 and 1.18-7.35, respectively, were obtained. The radical polyadditions of 1a with dithiols afford polymers containing a homopolymer of 1a, while those of 1b and 1c with dithiols afford polymers with a content of dithiol units of exactly 50 mol-%.
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  • 38
    Digitale Medien
    Digitale Medien
    Ge- and sn-containing poly(p-xylylene): synthesis, structure and thermal behavior (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2179-2184 
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    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Block copolymers of unsubstituted poly(p-xylylene)(PPX) and Ge- or Sn-organic bridged PPX (GePPX and SnPPX) were prepared by pyrolysis of specially synthesized organometallic p-cyclophane precursors followed by deposition and polymerization of the thus produced p-xylylene monomers. The copolymer structure and thermal behavior were investigated depending on deposition temperature (10 and -196°C). The copolymer PPX-GePPX obtained from solid monomers deposited at -196°C (2a) consists of long quasi-independent PPX and GePPX blocks and has paracrystalline structure. Thermal treatment of 2a near 160°C yields crystalline regions of PPX along with paracrystalline aggregates of GePPX. Pyrolysis of this system near 300°C in an inert atmosphere results in the formation of Ge crystals in PPX matrix. In contrast, the copolymer PPX-GePPX produced by simultaneous deposition and polymerization at 10°C (2a′) contains shorter blocks of PPX and GePPX than the copolymer deposited at -196°C. Copolymer 2a′ turns to the amorphous state during thermal treatment, and its pyrolysis does not lead to Ge-crystal formation; hence the supramolecular structure of the polymer plays an important role in inorganic phase formation. The copolymer PPX-SnPPX (2b) is formed only at a deposition temperature of -196°C; deposition at 10°C yields oligomeric resins. The structure of 2b is nearly the same as that of 2a; pyrolysis of 2b in air results in SnO2-crystal formation in a PPX matrix.
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  • 39
    Digitale Medien
    Digitale Medien
    PVC modification with pyridine groups. Synthesis, characterization and transformation to ionomers (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2199-2204 
    Details
    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The modification of PVC with 4-mercaptopyridine is described. The content of pyridine groups in the products is measured by NMR and IR spectroscopy. The degree of modification depends on the reaction conditions, and values of up to 70% are achieved without degradation or other appreciable side reactions. The tertiary amino groups in the polymer can be alkylated with iodides of varying chain length to form quantitatively quaternary pyridinium salt groups, leading to PVC ionomers and polyelectrolytes.
    Zusätzliches Material: 5 Ill.
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  • 40
    Digitale Medien
    Digitale Medien
    Free radical polymerization of a sugar residue-carrying styryl monomer with a lipophilic alkoxyamine initiator: synthesis of a well-defined novel glycolipid (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2193-2197 
    Details
    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Controlled free radical polymerization of N-p-vinylbenzyl-2,3,5,6-tetra-O-acetyl-4-O-(2,3,4,6-tetra-O-acetyl-β-D-galactopyranosyl)-D-gluconamide (Ac-VLA) was achieved by the nitroxide-mediated free radical polymerization with a lipophilic alkoxyamine “initiator” with a dioctadecyl group in 1,2-dichloroethane at 90°C. The polymerization proceeds in a “living” fashion, providing Ac-VLA polymers with low polydispersity. The hydrolysis of the polymers results in well-defined glycopolymer-carrying amphiphiles, viz., artificial “glycolipids”.
    Zusätzliches Material: 6 Ill.
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  • 41
    Digitale Medien
    Digitale Medien
    Synthesis of a diphenylethylene derivative carrying aromatic tertiary amine groups and its use in chain end functionalization of alkyllithium-initiated polymerizations (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2185-2191 
    Details
    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: 1,1-Bis[(4-dimethylamino)phenyl]ethylene was successfully synthesized through the ‘Wittigtype’ reaction of 4,4′-bis(dimethylamino)benzophenone with the ‘Tebbe’ reagent. The methylenation yields were over 80 wt.-% on the basis of the initial amount of benzophenone derivative used. Terminally functionalized polymers having aromatic tertiary amine groups at one end or at both ends were prepared by the crossover reactions of n-butyllithium (n-BuLi), poly(styryl)lithium (PSLi), and poly(isoprenyl)lithium (PILi) with the diphenylethylene analogue. The functionalization yields were over 87 mol.-% based on the results of 1H NMR spectroscopic analysis. The number-average molecular weights of the polymers based on the ratio [gram of monomer]/[mole of initiator] are in good accordance with those observed from size exclusion chromatographic and 1H NMR spectroscopic analysis (3,0 × 103 ∼ 7,5 × 103 g/mol).
    Zusätzliches Material: 7 Ill.
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  • 42
    Digitale Medien
    Digitale Medien
    Restriction of mobility in model liquid crystalline ionomers (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2205-2210 
    Details
    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Model liquid crystalline ionomers have been analyzed by SAXS both in bulk and in toluene solution. These compounds are referred to as liquid crystalline halatosemitelechelic polystyrenes (LC HSTP's) and consist of low molecular weight polystyrene chains end-capped at one end by a sulfonate group associated to a mesogenic counterion. The results are in agreement with a microphase separation between the polymer chain and the mesogenic counterion. The main characteristic feature of the SAXS profile for the bulk material is the so-called ionic peak, whose position obeys a general law which is in favor of a rod-like organization of the multiplets and which shows that the polymer chains are stretched in the very close vicinity of the mesogenic core, in agreement with the Eisenberg, Hird and Moore model for ionomers. The thickness of this region of restricted mobility has been estimated to 1 nm, which is the order of magnitude of the persistence length of polystyrene. This very local restriction in mobility persists in toluene solution, in contrast to what is observed for the ω-Li-sulfonato-polystyrene precursors. The results also agree with an isotropic distribution of the multiplets in toluene.
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  • 43
    Digitale Medien
    Digitale Medien
    Polymerization and asymmetric oligomerization of allylsilanes using chiral ethylenebis(4,5,6,7-tetrahydro-1-indenyl)zirconium and -hafnium complexes (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2211-2215 
    Details
    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Stereospecific polymerization and asymmetric oligomerization of allylsilanes were investigated by using C2- and Cs- symmetric zirconocene catalysts. Isotactic and syndiotactic poly(allylsilane)s were produced with rac-ethylenebis(4,5,6,7-tetrahydro-1-indenyl)zirconium dichloride (1) and diphenylmethylene(η5-cyclopentadienyl)(η5-fluorenyl)zirconium dichloride (6), respectively. Bulky allylsilanes afforded optically active oligomers in the reactions using optically active ethylenebis(4,5,6,7-tetrahydro-1-indenyl)zirconium and -hafnium complexes.
    Zusätzliches Material: 5 Ill.
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  • 44
    Digitale Medien
    Digitale Medien
    Microhardness under strain, 4. Reversible microhardness in polyblock thermoplastic elastomers with poly(butylene terephthalate) as hard segments (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2217-2220 
    Details
    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The microhardness (H) technique was recently applied to poly(butylene terephthalate) (PBT) and its multiblock copolymers for examination of the stress-induced polymorphic transition. Following these investigations the present study attempts to observe the reversible variation of microhardness under strain. For this purpose bristles of drawn and annealed (at 160°C in vacuum) poly(ether ester) (PEE) were characterized with respect to their microhardness at various stages of tensile deformation. H was measured under and after loading (σ) in deformation steps of 5% each. In accordance with previous results on PBT and PEE, H values at σ ≠ 0 show a sharp drop (by 40%) in a relatively narrow deformation interval (ε = 10-15%), owing to the stress-induced α ⇔ β polymorphic transition. The hardness measurements at σ = 0 show a continuous decrease of H with a remaining strain. H values at σ = 0, corresponding to plastic deformation up to 5%, are much higher than the corresponding ones taken under stress at an overall deformation between 10 and 25%. The higher H values are explained by the regeneration of the starting α modification. Results reveal that in materials characterized by high and reversible deformability it is possible to observe a reversible microhardness behaviour, provided the strain-induced structural changes are reversible.
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  • 45
    Digitale Medien
    Digitale Medien
    Living ring-opening isomerization polymerization of 2,3,5,6-tetrahydroimidazo[2,1-b][1,3]oxazole with sulfonate initiators (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2237-2246 
    Details
    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The cationic ring-opening isomerization polymerization of a bicyclic pseudourea, 2,3,5,6-tetra-hydroimidazo[2,1-b][1,3]oxazole (1), was examined. The polymerization of 1 with methyl trifluoromethane-sulfonate or p-toluenesulfonate proceeds even at -40°C and gives poly(1,3-oxazolidin-2-one-1,3-diylethylene) (2) in high yield. Postpolymerization experiments revealed that the present polymerization proceeds in a “living” fashion. The mechanism of the polymerization was determined from in situ 1H NMR measurements as well as kinetic analysis, which proved that the polymerization proceeds via ionic propagating species, although the apparent propagating species in the polymerization with methyl p-toluenesulfonate is covalent.
    Zusätzliches Material: 8 Ill.
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  • 46
    Digitale Medien
    Digitale Medien
    Radiation-induced radical formation and crosslinking in aqueous solutions of N-isopropylacrylamide (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2229-2235 
    Details
    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: To investigate chain-initiating and crosslinking mechanisms, radical formation in dilute aqueous solutions of N-isopropylacrylamide (NIPAAm) and poly-NIPAAM was studied using electron pulse radiolysis with optical detection at room temperature. Several transients of NIPAAm generated by reactions with electrons, hydroxyl radicals and hydrogen atoms were observed. Electron attachment to the carboxyl group (ke = 9.0 x 109 dm3 · mol-1 · s-1) forms the radical anion, which undergoes fast and reversible protonation (pKa = 7.8) at the carboxyl oxygen. At pH 〉 pKa, slow and irreversible protonation of the electron adduct at the vinyl group leads to the α-carboxyalkyl radical CH3(.CH)CONHCH(CH3)2, which is also formed by addition of H atoms to NIPAAm (kH = 7.3 × 109 dm3 · mol-1 · s-1). Addition of OH radicals (kOH = 5.4 × 109 dm3 · mol-1 · s-1) forms CH2(OH)(.CH)CONHCH(CH3)2. Hydrogen abstraction was not observed in the case of NIPAAm monomer, but it was found for the reaction of OH radicals with thermally polymerized NIPAAm. Semi-empirical quantum chemical calculations support the assignment of the observed spectra to the radicals. A reaction mechanism for the formation of crosslinks is discussed.
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  • 47
    Digitale Medien
    Digitale Medien
    Homopolymerization and copolymerization of styrene and norbornene with Ni-based/MAO catalysts (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2221-2227 
    Details
    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The homopolymerization of styrene (Sty) and norbornene (NBE) was investigated in the presence of the nickel stearate (NiSt)/methylaluminoxane (MAO) catalytic system in toluene and in chlorobenzene at 20°C. The fully saturated structure of polynorbornene indicates that the two monomers polymerize by an ethylenic type addition reaction. The synthesis of true copolymers shows that one type of active species is operating for the tow monomers. Determination of reactivity ratios (rNBE = 20.8 and rSty = 0.02) indicates a much higher reactivity of NBE, which is interpreted by a coordination mechanism. The styrene-norbornene copolymers exhibit glass transition temperatures (Tg) which range from 100°C to 320°C and follow Kovacs' law. The absence of crystallinity and the homogeneous repartition of monomer units along the chains yield highly transparent materials of high thermal stability.
    Zusätzliches Material: 8 Ill.
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  • 48
    Digitale Medien
    Digitale Medien
    Methacrylate networks containing chiral calamitic liquid crystalline side groups (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2247-2254 
    Details
    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: A one-step copolymerization of ferroelectric methacrylate monomers leading to networks is presented. Oriented networks are obtained and electro-optical investigations are described. Smectic C* and another smectic phase are found in slightly crosslinked networks. For higher crosslinking densities, only the high temperature smectic C* phase was found. Electro-optical measurements were performed on the networks, and significant changes in the ferroelectrical properties were found. For crosslinking densities higher than 0.5 mol-%, switching times increased dramatically and the spontaneous polarization decreased. Networks with crosslinking densities of 2 mol-% did not exhibit ferroelectric properties.
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  • 49
    Digitale Medien
    Digitale Medien
    Reactive groups on polymer coated electrodes, 8. Novel conducting polymer interfaces produced by electrochemical copolymerization of functionalized thiophene activated esters with 3-methylthiophene (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2255-2266 
    Details
    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: With the synthesis of two new functionalized thiophene activated esters and their electrocopolymerization with 3-methylthiophene, two types of redox active polymers have been prepared. FTIR studies of the resultant polymers reveal that both types of activated ester groups withstand the applied electrooxidative conditions and are correctly integrated into the corresponding polymers. The electrocopolymerization experiments show that the composition of the obtained polymers strongly depends on the ratio of the components in the reaction medium. With the increase of the ratios of pentafluorophenyl thiophene-3-acetate-3-methylthiophene or succinimido thiophene-3-acetate/3-methylthiophene, a higher concentration of functionalized thiophene units is incorporated into the polymer chains. The measurement of the conductivity on these polymeric films gave a value in the range of 10-3 to 10-2 S · cm-1, which is comparable to that of the unsubstituted polythiophene and consistent with the conjugation grade suggested by electrochemical and UV-vis spectroscopic data. As expected, the pendant reactive ester groups on the electrode surfaces react rapidly with different amino compounds without loss of the electroactivity of the polymers. Therefore, these novel polymeric materials can be used as electrode interfaces for further functionalizations, especially for the immobilization of amines, peptides, and enzymes.
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  • 50
    Digitale Medien
    Digitale Medien
    A novel modification of poly(L-lysine) leading to a soluble cationic polymer with reduced toxicity and with potential as a transfection agent (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2565-2575 
    Details
    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Chemical modification of poly(L-lysine) by hydrogen transfer addition of N,N-dimethylacrylamide to the primary amino groups results in new water soluble derivatives with reduced cell toxicity which maintain basic properties. Kinetic studies on the addition reaction were performed using model compounds, and a reliable kinetic model was obtained which proved to be valuable also in the case of poly(L-lysine). A peculiar feature of the addition reaction of poly(L-lysine) on N,N-dimethylacrylamide is that, starting from partially protonated poly(L-lysine), the reaction stops after that all the unprotonated units originally present have reacted. Toxicological studies on modified poly(L-lysine) in comparsion with parent poly(L-lysine) showed that the modifying reaction leads to a reduction in toxicity.
    Zusätzliches Material: 10 Ill.
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  • 51
    Digitale Medien
    Digitale Medien
    Synthesis, characterization and hydrolysis of poly[styrene-co-(6-methylene-1,4-oxathiepane-7-one)] and poly[styrene-co-(6-methylene-5-methyl-1,4-oxathiepane-7-one)] (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2577-2582 
    Details
    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Vinylic-type polymers bearing ester groups inside the polymer backbone have been synthesized by free radical copolymerization of styrene (St) and 6-methylene-1,4-oxathiepane-7-one (MOTPO) or 6-methylene-5-methyl-1,4-oxathiepane-7-one (MMOTPO). The addition-fragmentation ring-opening polymerization of both MOTPO and MMOTPO leads to the formation of ester linkages located inside the vinylic polymer backbone. A strong decrease of the molar mass of the copolymer has been observed when the copolymers were dissolved in a mixture of THF and water in the presence of sodium hydroxide. This decrease can be attributed to the hydrolysis of the ester linkages, as followed by size exclusion chromatography (SEC). The molar mass of the degraded polymer samples was correlated with the number of ester linkages in the backbone, showing that only a fraction of these ester groups have been hydrolyzed.
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  • 52
    Digitale Medien
    Digitale Medien
    Unique morphologies found in freeze-dried poly(ethylene oxide) prepared from dilute solutions (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2597-2600 
    Details
    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Freeze-dried particles of poly(ethylene oxide) (PEO) were prepared from sublimation of a 1 × 10-2 wt.-% solution of PEO in benzene in an ice-salt bath. After isothermal crystallization at 318.2 ± 0.1 K for 2 h, an unusual planar zigzag form of PEO was found. A variety of unique spherulite-like morphologies were also observed, and their formation is discussed on the basis of the interaction between solvent molecules and segment of the polymer chains.
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  • 53
    Digitale Medien
    Digitale Medien
    Effect of filler on kinetics and energy of activation of phase separation in poly(methyl methacrylate)/poly(vinyl acetate) blend (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2609-2612 
    Details
    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The effect of a filler on the rate and energy of activation of phase separation was studied for binary poly(methyl methacrylate)/poly(vinyl acetate) blends (system with LCST) using light scattering. It was found that the rate of phase separation of the filled blends at close quench depth ΔT = T-Ts is much lower as compared with the unfilled one at close quench depth. The activation energy for the filled blends is lower than that of unfilled blends. The drop of the rate of phase separation and of the activation energy in filled systems is explained by the formation of a border layer at the interface with solid where molecular packing is less dense and molecular mobility is restricted in comparison with unfilled polymer. Equal rates of phase separation or the equilibrium state may be achieved at higher quench depth for the filled blend.
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  • 54
    Digitale Medien
    Digitale Medien
    Reduction of the cationic growing center of polyisobutylene by activated magnesium. Block copolymerization of isobutylene with tert-butyl methacrylate (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2619-2623 
    Details
    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Transformation of the tert-chlorine end group of poly(isobutylene) into a terminal Grignard group was studied with the motivation of producing a PIB macroanion. The reduction of the terminal tert-chlorine group was completed within 30 min at room temperature by using activated magnesium (Mg*) prepared by the reaction of MgCl2 with lithium naphthalenide. The efficiency of the transformation was 28%, which was determined by end-group analysis of the polymer obtained after quenching the reduction with methyl 2-phenylacetate in the presence of CeCl3. The terminal carbanion prepared by this method initiated the polymerization of tert-butyl methacrylate (TBMA) to give a block copolymer consisting of an anionically and a cationically polymerizable monomer.
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  • 55
    Digitale Medien
    Digitale Medien
    The characterization of the interfacial reaction in polyamide 1010/poly(propylene)-graft-(glycidyl methacrylate) blends (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2631-2634 
    Details
    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Binary blends of polyamide 1010/poly(propylene) and polyamide 1010 (PA1010)/poly(propylene)-graft-(glycidyl methacrylate) (PP-g-GMA) were prepared. The epoxy groups in PP-g-GMA react with the amino end-groups in PA1010, thus a PA1010-graft-PP copolymer is formed and acts as a compatibilizer between PA1010 and PP-g-GMA. The reaction was confirmed by electron spectroscopy for chemical analysis (ESCA) and attenuated total reflection (ATR)-FTIR spectroscopic analysis, and also evaluated by the stability of the suspension obtained by dissolving the blends in formic acid and by the morphologies of the blends.
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  • 56
    Digitale Medien
    Digitale Medien
    Structure-property relationships of core-shell type waterborne polyacrylate-polyurethane microemulsions (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2635-2640 
    Details
    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Different cross-linking types of core-shell types waterborne polyacrylate-polyurethane (PAC-PU) microemulsions, in which polyurethane acts as the shell of the latex particles and a copolymer of acrylate monomers as the core, were synthesized. In the anionic polyurethane film. there is a certain degree of softhard phase mixing and different extents of short-range order of the hard segments. The introduction of a polyacrylate core increases the soft-hard phase separation in the polyurethane and breaks the short-range order of the hard segments in polyurethane to some extent. The hard segments in the shell and the core cause a widened tan δ peak. This peak shifts to higher frequencies as the core-shell ratio increases and also when a Type A or Type B cross-linking structures exist. The cross-linking structure, especially Type B, improves the soft-hard separation and the phase mixing of the core and the hard segments in the shell and at the same time breaks the short-range order in the hard segments. The cross-linking structure does not affect the thermogravimetric properties of the PAC-PU films.
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  • 57
    Digitale Medien
    Digitale Medien
    An approach to hyperbranched polymers with a degree of branching of 100%Dedicated to the memory of Prof. Dr. Reimund Stadler (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2655-2664 
    Details
    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: General guidelines for the design of monomers for the synthesis of hyperbranched polymers without linear units are presented. The synthesis of one monomer fulfilling these requirements and the first results of the polymerization of this monomer are described. 4-(3-Maleimidopropoxy)-4′-methoxybenzaldehyde azine was used as a monomer of the AB2-type in a “criss-cross” cycloaddition with the maleimide group as A-function and the azine as two B-groups. Melt condensation of this monomer gave a polymer (Mn = 5700) which showed 1H and 13C NMR spectra corresponding well to the expected completely branched structure.
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  • 58
    Digitale Medien
    Digitale Medien
    Swelling behavior of polyelectrolyte gels in the presence of salts (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2665-2670 
    Details
    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The swelling behavior of weakly crosslinked polyelectrolyte gels based on sodium methacrylate (PMA) and diallyldimethylammonium chloride (DADMAC) in aqueous medium was studied in the presence of different types of salts (NaCl, arginine hydrochloride, cetylpyridinium chloride (CPC), sodium dodecyl sulfate (SDS), and sodium dodecylbenzenesulfonate (SDBS)). It is shown that, starting from some characteristic concentration of a salt, a further increase of the salt concentration results in the shrinking of the gels. This characteristic concentration is defined by the gel parameters (polymer concentration in the gel that is a function of the monomer concentration at the conditions of hydrogel synthesis) and does not depend on the kind of salt used, except for the system polyelectrolyte gel/oppositely charged surfactant (PMA-CPC and DADMAC-SDS or SDBS). It is shown that the initial rate of gel shrinking for all studied systems, including the system gel/oppositely charged surfactant, is determined by the salt concentration and the gel parameters. For the systems PMA-CPC and DADMAC-SDS the gel collapse is a two-step process.
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  • 59
    Digitale Medien
    Digitale Medien
    Ni(acac)2-DAD/MAO: A new catalytic system for ethylene polymerization (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2677-2681 
    Details
    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The halide-free combination of Ni(acac)2 and DAD(diazadiene, ArN=CH—CH=NAr, where Ar = 2,6-C6H3(i-Pr)2) is active for ethylene polymerization in the presence of methylaluminoxane (MAO). The performance of this new catalytic system was evaluated with respect to activity and polymer structure. The degree of branching of the obtained polyethylenes is substantially influenced by the polymerization conditions. The activation mechanism was investigated by 1H NMR. MAO is proposed to participate in the ligand exchange process.
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  • 60
    Digitale Medien
    Digitale Medien
    Effect of a triblock PCL-PDMS-PCL copolymer on the properties of immiscible poly(vinyl chloride)/poly(2-ethylhexyl acrylate) blends (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2699-2708 
    Details
    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Miscibility, thermal, mechanical and morphological properties of poly(vinyl chloride)/poly(2-ethylhexyl acrylate), (PVC/PEHA) blends containing 1-10 wt.-% of the triblock copolymer polycaprolactone-block-poly(dimethylsiloxane)-block-polycaprolactone (PCL-PDMS-PCL, Tegomer) were investigated by several techniques. Binary blends of PVC/PEHA are found to be immiscible according to differential scanning calorimetry and viscosity measurements. The effect of Tegomer addition on the properties of blends was examined. Ternary blends of PVC/PEHA/Tegomer exhibited a single Tg behaviour and viscosity measurements indicate some compatibility. Stress-strain results showed that Tegomer has a synergetic effect on the flexibility of the blends. FTIR analysis confirms the specific interactions between the components in ternary blends of PVC/PEHA/Tegomer. Morphological properties of the blends were examined by scanning electron microscopy.
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  • 61
    Digitale Medien
    Digitale Medien
    Determination of titanium distribution on the catalyst surface of industrial supported Ziegler catalysts by means of scanning auger electron microscopy (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2709-2715 
    Details
    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Scanning Auger electron microscopy (SAM), which is one of the best surface analytical methods, was applied to achieve basic understandings of the surface distribution of titanium species on supported Ziegler catalysts. Three different types of supported Ziegler catalysts were prepared by grinding MgCl2 with TiCl4 (Cat-A), by grinding MgCl2 with ethyl benzoate (EB) followed by the reaction with TiCl4 (Cat-B), and by reacting TiCl4 with a mixture of Mg(OEt)2 and dibutyl phthalate (DBP) (Cat-C). The SAM analysis revealed that the titanium species were scattered over the surface of Cat-A, while the distribution of the titanium species was rather even on the surface of Cat-B. In the case of Cat-C, the titanium species were found to exist evenly on the surface, and all particles of the catalyst showed a similar tendency. Hence, the influence of the preparation method of the catalyst on the distribution of the titanium species is clearly observed by SAM. Models of the catalyst particles obtained by different preparation methods were proposed on the basis of the results.
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  • 62
    Digitale Medien
    Digitale Medien
    Crosslinked poly(styrenesulfonamide) with iminoacetic acid chelating groups for hard-water treatment (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2731-2735 
    Details
    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Chlorosulfonated polystyrene-DVB (10%) copolymer (in beads form, 720-840 μm) has been modified with triethylenetetramine (TETA) to give the corresponding polymeric sulfonamide. By treating with the potassium salt of chloroacetic acid in water, amino groups of the polymer have been carboxymethylated almost quantitatively. The resulting material with iminoacetic acid pendant groups has very efficient chelating ability for Ca(II) and Mg(II) ions in ppm levels. The chelating polymer can be regenerated ten times by acid leaching without losing its original reactivity. It is suitable for removal of calcium and magnesium ions to supply soft water.
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  • 63
    Digitale Medien
    Digitale Medien
    Bis(4-monosubstituted-5(4H)oxazolinones) as coupling agents for block copolymer synthesis: reaction with hydroxy-terminated oligomers (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2747-2753 
    Details
    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The bulk chain-coupling reactions between hydroxy-terminated poly(oxytetramethylene), poly(oxyethylene), or poly(ε-caprolactone) and several bis(4-monosubstituted-5(4H)oxazolinones) were studied. The polyaddition reaction proceeds rapidly and without side reactions when a catalytic amount of Ti(OBu)4 is used in the case of poly(oxytetramethylene) or poly(ε-caprolactone). On the other hand, the efficiency of the chain extension was much lower in the case of poly(oxyethylene). An explanation involving the coordination of poly(oxyethylene) oxygen atoms at the active sites of tetrabutoxytitanium is put forward. High molar mass block copolymers were synthesized by the chain-coupling reaction of mixtures of α,ω-dihydroxy-poly(oxytetramethylene) and -poly(ε-caprolactone) with bis(oxazolinones). The differential scanning calorimetry (DSC) study of the block copolymers revealed the existence of a microphase separation between the two blocks when the starting polymers have Mn ≥ 1000. For lower molar mass polymers amorphous products were obtained.
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  • 64
    Digitale Medien
    Digitale Medien
    Determination of the content of extended chain segments in isotropic and uniaxially stretched polyethylenes by raman spectroscopy (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2767-2776 
    Details
    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The Raman spectrum of polyethylene is known to be mainly sensitive to the conformational state of the polymer chain. At room temperature, most of the vibrations of the polyethylene Raman spectrum are intrinsically reflecting only one-dimensional order along the chain length. Based on the latter, we propose a straightforward quantitative procedure for the calculation of the content of extended (all-trans) and non-extended chain segments by using the C—C asymmetric stretching, the —CH2— twisting and the —CH2— wagging vibrations. The applicability of this procedure is demonstrated by using a set of samples covering a wide range of densities which, in addition, were subjected to uniaxial stretching and annealing. The results suggest that a significant portion of extended chain segments is placed outside the crystalline domains. Besides, in stretched samples, an important increase in the extended chain segments content was found. This is likely caused by the presence of highly oriented chain segments in the non-crystalline regions. These further disappeared as the stretched samples were annealed.
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  • 65
    Digitale Medien
    Digitale Medien
    Cationic polymerization of 1,3-pentadiene initiated with aluminium chloride in non-polar solvent: study of the initiation mechanism (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2533-2539 
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    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The cationic polymerization of 1,3-pentadiene initiated with aluminium chloride was studied in a non-polar solvent. Experiments carried out in the presence of 2,6-di-tert-butylpyridine (DtBP) clearly demonstrated that the major initiation process is the direct initiation mechanism, even though the existence of a cocatalytic mechanism to small extent cannot be rejected. This result is also evidenced by the linear dependence of the conversion on AlCl3 concentration, and by experiments carried out in the presence of hydrogen chloride showing the independence of the polymerization yield on the hydrogen chloride concentration.
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  • 66
    Digitale Medien
    Digitale Medien
    Compatibilizing effect of polystyrene-block-poly(4-vinylpyridine) for poly(2,6-dimethyl-1,4-phenylene oxide)/chlorinated polyethylene blends (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2625-2630 
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    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The compatibilizing effect and mechanism of compatibilization of the diblock copolymer polystyrene-block-poly(4-vinylpyridine) P(S-b-4VPy) on immiscible blends of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO)/chlorinated polyethylene (CPE) were studied by means of scanning electron microscopy (SEM), differential scanning calorimetry (DSC), mechanical properties and FTIR measurements. The block copolymer was synthesized by sequential anionic polymerization and melt-blended with PPO and CPE. The results show that the P(S-b-4VPy) added acts as an effective compatibilizer, located at the interface between the PPO and the CPE phase, reducing the interfacial tension, and improving the interfacial adhesion. The tensile strength and modulus of all blends increase with P(S-b-4VPy) content, whereas the elongation at break increases for PPO-rich blends, but decreases for CPE-rich blends. The polystyrene block of the diblock copolymer is compatible with PPO, and the poly(4-vinylpyridine) block and CPE are partially miscible.
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  • 67
    Digitale Medien
    Digitale Medien
    Synthesis and characterization of branched polypropenes obtained by metallocene catalysis (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2647-2653 
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    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The homopolymerization of propene, 4-methyl-1-pentene, 1-octene and the copolymerization of propene with 4-methyl-1-pentene and 1-octene, respectively, was carried out with the isospecific metallocene catalyst system rac-[(dimethylsilylene)bis(2-methylbenzo(e)indenyl)]zirconium dichloride/methylaluminoxane at 30°C in toluene. By variation of the monomer ratio, it is possible to produce copolymers in the entire composition range. The activity, the amount of comonomer insertion, and the molecular masses obtained in the propene/1-octene copolymerization are significantly higher compared to the respective values of the system propene/4-methyl-1-pentene. It is possible to synthesize polymers with glass transition temperatures ranging from -65 up to 26°C. Whereas the incorporation of more than 20 mol-% 1-octene leads to amorphous polymers, the propene/4-methyl-1-pentene copolymers with less than 15 and more than 60 mol-% 4-methyl-1-pentene are semicrystalline. All melting points vary in the range from 50 to 225°C. Wide angle X-ray scattering measurements indicate an increase of the γ-modification compared to the γ-modification with increasing comonomer content and crystallization temperature. Typical supermolecular morphologies different from spherulites and known for the γ-phase of the isotactic polypropene homopolymer are observed for the copolymers by polarized light microscopy.
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  • 68
    Digitale Medien
    Digitale Medien
    Sub-Tg annealing of the clathrate δ form of syndiotactic polystyrene (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2671-2675 
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    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Amorphous films of syndiotactic polystyrene were crystallized in dichloromethane, to obtain samples in the clathrate δ form; successively the samples were either annealed at temperatures below the glass transition temperature (Tg) or extracted with acetone. The samples obtained show, in the X-ray analysis, crystalline structures tending toward the “emptied” δ form, free of solvent molecules, as already described for sPS. The study of the transport properties, diffusion and sorption of dichloromethane vapor, shows that the annealed samples are characterized by a slightly lower diffusion coefficient, but much higher sorption at low activity of the vapour. This high sorption is explained by the penetration of solvent molecules both into the amorphous and the “emptied” crystalline phase, producing again the clathrate form at low vapour activity. The high sorption capability makes these samples promising as sorption media to remove traces of polluting chlorinated solvents both in the liquid and in the vapour phase.
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  • 69
    Digitale Medien
    Digitale Medien
    Preparation of new rigid backbone conjugated organic polymers with large fluorescence quantum yields (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2683-2688 
    Details
    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Palladium-catalyzed cross-coupling reactions between 5,5′-dibromo-2,2′-bipyridine and substituted phenyldiacetylenes provide a novel family of rigid backbone conjugated polymers 4a, 4b. The weight-average molecular weight determined by GPC, polystyrene standards, Mw was 23 350 g · mol-1 for 4a and 13 460 g · mol-1 for 4b, with a polydispersity index of 2.7 and 1.9, respectively. The highly luminescent polymers exhibit excellent solubility and can readily be processed into transparent films. The model compounds 5 and 6 show a fluorescence quantum yield close to unity.
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  • 70
    Digitale Medien
    Digitale Medien
    Ester-carbonate interchange reaction in the solid state: synthesis of poly(ester-carbonate) (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2689-2697 
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    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Poly(ethylene terephthalate-co-bisphenol A carbonate) was synthesized by ester-carbonate interchange reaction in the solid state. The polymerization reaction was carried out by heating two chemically distinct oligomers, namely, poly(aryl carbonate) and poly(ethylene terephthalate) in the temperature range of 180-230°C, during which period both chain extension as well as interchange reactions occurred. A copolymer of ηinh = 0.84 dL/g was obtained. With the progress of the interchange reaction the Tg of the copolymer slowly increases and reaches a maximum value of 102°C. The oligomer mixture, which exhibits initially two distinct Tm's, shows a single Tm at the end of the reaction. Formation of copoly(aryl ester-carbonate)s by an ester-carbonate interchange reaction was also found in the solid state at temperatures below 230°C. High molecular weight poly(aryl ester-carbonate)s with a Tg = 163°C and ηinh = 0.52 dL/g were prepared from the corresponding low molecular weight oligomers of poly(aryl ester) and poly(aryl carbonate)s.
    Zusätzliches Material: 10 Ill.
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  • 71
    Digitale Medien
    Digitale Medien
    Synthesis of poly(arylene ether ketone)s containing amide side groups via nitro displacement reaction (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2717-2721 
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    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: New amorphous poly(arylene ether ketone)s with amide substituents were prepared via nucleophilic nitro displacement reaction. The dinitro monomer, 1,4-bis[4-nitro-3-(1-piperidylcarbonyl)benzoyl]benzene, was synthesized through a masked acyl anion equivalent, bis(aminoacetonitrile). The weight average molecular weight (Mw) of the polymers is about 40 000, the glass transition temperature around 200°C. The polymers are soluble in common organic solvents such as chloroform, 1,1,2-trichloroethane, and N-methyl-2-pyrrolidone (NMP). The polymer from the dinitro monomer and bisphenol A is easily cast into a transparent and flexible freestanding film. 5% weight loss temperatures of the polymers are in the range from 409-418°C under N2.
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  • 72
    Digitale Medien
    Digitale Medien
    Synthesis of photoreactive α-4-azidobenzoyl-ω-methoxy-poly(ethylene glycol)s and their end-on photo-grafting onto polysulfone ultrafiltration membranes (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2723-2729 
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    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Covalent end-on grafting of poly(ethylene glycol) (PEG) onto a polysulfone (PSf) surface using α-4-azidobenzoyl-ω-methoxy-PEG (ABMPEG) is described. Photoreactive ABMPEG was synthesized by reacting monomethoxy-PEG (MPEG) with 4-azidobenzoyl chloride, yielding complete substitution of the hydroxyl groups. After adsorption from aqueous solutions, ABMPEG was photo-grafted under wet conditions onto PSf ultrafiltration (UF) membranes. Contact angle (CA) measurements showed the increased hydrophilicity of modified membranes and the irreversibility of the modification. Bovine serum albumin (BSA) adsorption decreased by 70% and the permeability decay after protein adsorption became less severe for the modified membranes compared to unmodified reference membranes.
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  • 73
    Digitale Medien
    Digitale Medien
    Synthesis and electropolymerization of new p-nitrophenyl-functionalized thiophene derivatives (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2737-2746 
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    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Electrooxidative polymerization of three new p-nitrophenyl-functionalized thiophene derivatives leads to materials which show the electroactivities of both nitrobenzene and polythiophene. However, other than the reversible redox transition in solution, the nitro groups exhibit a complex nature of the cyclic voltammetric curve in the obtained solid polymeric films. It was found that the electrochemical behavior of the nitro groups has a dramatic effect on the conjugated π-electron systems of the substituted polythiophenes. Upon electrochemical addressing of the nitro groups the electroactivities of the corresponding polymers decrease rapidly compared to their analogous polymers without nitro groups. FTIR studies of these polymers revealed that after the reduction/oxidation process of the nitro groups still a large amount of electrolyte salt remains in the polymer films. As typical of functionalized polythiophenes, however, these new polymers can be switched under controlled conditions between their oxidized and neutral forms and exhibit the typical properties of electroactive polythiophenes, e.g., electrochromism.
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  • 74
    Digitale Medien
    Digitale Medien
    Polyesters bearing furan moieties, 2Part 1: cf.ref.1. A detailed investigation of the polytransesterification of difuranic diesters with different diols (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2755-2765 
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    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: A two-step transesterification procedure was applied to combinations of difuranic diesters and both aliphatic and furanic diols. The reaction parameters (including the nature of the catalyst) were varied in both phases of the process and the results compared with those published for similar systems based on aromatic diesters. The best results related to the first phase of the synthesis were obtained using Zn(AcO)2, Pb(AcO)2 or Ti(OBu)4 at 200°C with a large excess of diol. The second phase, which led to the actual polymer at 200-240°C, called upon the catalytic action of SnC2O4, Sb2O3 and Ti(OBu)4 and was prolonged until the viscosity of the media ceased to increase. Specific problems, related to some fragile moieties, limited the success of these polymerizations to a number of combinations which gave polyesters bearing regular structures and molecular weights in the tens of thousands.
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  • 75
    Digitale Medien
    Digitale Medien
    Design, characterization and processing of cellulose-S-acetyl: a precursor to an electroactive cellulose (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2777-2783 
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    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The synthesis and characterization of Cell-SAc 3, a cellulose isopentyl (IP) ether with additional pendant S-acetyl (SAc) moieties (degree of substitution DSIP = 2.5, DSSAc = 0.4) are reported. Cell-SAc forms stable monolayers at the air-water interface once spread from dilute chloroform solution. The pressure-area isotherm of Cell-SAc is nearly identical to the parent Cell-IP 1, both exhibiting an expanded liquid phase at surface areas of 70 and 67 Å, respectively. The similarity of the two isotherms shows that the presence of the S-acetyl substituent does not result in an increase in the molecular area, at which the liquid-crystal analogous phase occurs. This observation suggests that the side-chains with the pendant S-acetyl group are oriented away from the water surface. Monolayers of Cell-SAc can be efficiently transferred onto silicon and hydrophobized glass or quartz substrates by a downstroke and upstroke technique. Resulting multilayers were characterized using X-ray reflection, FTIR, and UV-vis spectroscopy. The presence of S-acetyl moieties was found to increase the monolayer thickness relative to the parent Cell-IP. The cleavage of the S-acetyl group within the LB film is reported.
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  • 76
    Digitale Medien
    Digitale Medien
    Tissue-compatible multiblock copolymers for medical applications, controllable in degradation rate and mechanical properties (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2785-2796 
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    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: A class of degradable, phase-segregated multiblock copolymers is presented. The new copoly(ester-urethane)s, termed DegraPolTM/btgc, consist of crystallizable poly[(3-R-hydroxybutyrate)-co-(3-R-hydroxyvalerate)]-segments and amorphous segments from ε-caprolactone, diglycolide and ethylene glycol. As junction unit an aliphatic diisocyanate, TMDI, is applied. The copoly(ester-urethane)s are thermoplastic elastomers (Tm = 120-136°C) and are processable without degradation. For medical applications, materials are needed in which the degradation rate and the mechanical properties are independently adjustable to the medical needs. The mechanical properties of DegraPolTM/btgc, e.g., elasticity and toughness, can be controlled by the weight fraction of crystallizable segment; the elastic moduli of DegraPol/btcg are adjustable between 50 MPa and 500 MPa and were only little influenced by the chemical structure and the composition of the soft segment. By insertion of ‘weak links’ in the form of easily hydrolyzable glycolyl-glycolate ester bonds into the amorphous segments, we attempted to synthesize degradable polymers in which the hydrolytic degradation rate can be controlled by the amount and the sequence distribution of these bonds. We report on the synthesis and on the thermal and mechanical properties of such polymers.
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  • 77
    Digitale Medien
    Digitale Medien
    New chitin-based polymer hybrids, 3Part 2: cf. ref.4. Miscibility of chitin-graft-poly(2-ethyl-2-oxazoline) with poly(vinyl alcohol) (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2805-2811 
    Details
    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The miscibility of blends of poly(vinyl alcohol) (PVA) with chitin-graft-poly(2-ethyl-2-oxazoline) (1) and poly(2-ethyl-2-oxazoline) homopolymer (PEtOZO) was investigated. Calorimetric results showed a single glass transition temperature (Tg) in the entire range of compositions for both blend systems, which indicated that PVA is miscible with both the graft copolymer 1 and PEtOZO. The Tg of PVA is also shifted to lower temperature upon blending with the graft copolymer 1. IR analysis revealed the existence of specific interactions via hydrogen bonding between the hydroxyl groups in PVA and the carbonyl groups in the poly(2-ethyl-2-oxazoline) side chain of graft copolymer 1. The results show that the interaction of graft copolymer 1 with PVA is increased by introduction of longer poly(2-ethyl-2-oxazoline) side chains. Thermal decomposition (TG) measurements supported the compatibility of PVA with graft copolymer 1 and with PEtOZO, and showed that the thermal stability of PVA is improved upon blending with 1 or PEtOZO.
    Zusätzliches Material: 6 Ill.
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  • 78
    Digitale Medien
    Digitale Medien
    Moisture transport studies on newly developed aromatic and aromatic/aliphatic copolyester thin films (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1025-1035 
    Details
    ISSN: 0887-6266
    Schlagwort(e): polymer thin films ; thermosets ; microelectronics ; moisture ; physical aging ; Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: In polymers for microelectronics applications, moisture is known to have a deleterious effect upon device reliability. In this paper, the moisture transport behaviors of a newly developed family of all-aromatic and aromatic/aliphatic copolyester thermosetting films were described. The moisture uptake as a function of temperature, relative humidity, sample thickness, and processing conditions were presented via conjugate moisture sorption tests.1 It was found that the post curing near but below Tg resulted in an increase in both total moisture uptake and diffusion coefficient due to the effect of physical aging and the generation of sample defect volume. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1025-1035, 1998
    Zusätzliches Material: 18 Ill.
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  • 79
    Digitale Medien
    Digitale Medien
    Pressure-volume-temperature properties and free volume parameters of PEO/PMMA blends (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1061-1080 
    Details
    ISSN: 0887-6266
    Schlagwort(e): polymer blends ; dilatometry ; free volume ; specific volume ; excess volume ; compressibility ; thermal expansivity ; equation of state ; scaling parameters ; crystallinity ; glass transition ; Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Melt-miscible polymer blends of poly(ethylene oxide)/atactic poly(methyl methacrylate (PEO/a-PMMA)) were prepared by melt-mixing and characterized by pressure-volume-temperature (PVT) dilatometry in the pressure and temperature range of 0 to 200 MPa and 20 to 200°C, respectively. The PVT data were analyzed in terms of two equations of state (EOS). The empirical Tait EOS was applied in the glassy, semicrystalline, and equilibrium melt state, and the Simha-Somcynsky EOS theory was applied in the equilibrium melt and glassy state. The Simha-Somcynsky EOS theory contains a free volume function. The temperature, pressure, and composition dependence of the free volume fraction h calculated from the Simha-Somcynsky EOS theory was studied. As a function of blend composition we observe that the free volume fraction, thermal expansivity, and compressibility all deviate mainly positively from linearity while the specific volume deviates mainly negatively from linearity. These findings are reconciled with composition-dependent free volume parameters, the free volume and cell volume as well as with self- and cross-interaction parameters derived from the Simha-Somcynsky EOS theory as applied to polymer mixtures. Moreover, the pressure dependence of glass and melting transitions as well as crystallization kinetics have been investigated. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1061-1080, 1998
    Zusätzliches Material: 18 Ill.
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  • 80
    Digitale Medien
    Digitale Medien
    VTF to arrhenius crossover in temperature dependence of conductivity in (PEG)xNH4ClO4 polymer electrolyte (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1201-1209 
    Details
    ISSN: 0887-6266
    Schlagwort(e): polymer electrolytes ; NMR ; conductivity ; glasses ; Arrhenius and VTF dependences ; Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: We have studied the temperature variation of conductivity and 1H NMR linewidth of (PEG)xNH4ClO4 (x = 20, 30, 46, 100, 200, & 1000) polymer electrolyte systems. The temperature dependence of the conductivity shows two distinct behaviors, the low temperature VTF dependence crossing over to Arrhenius dependence at higher temperatures. The departure from the VTF behavior is found to be composition dependent. NMR spectra indicate the presence of large fractions of crystalline regions that start to melt around the crossover temperature. We understand the deviation from the VTF behavior as a consequence of this crystalline to elastomer transition. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1201-1209, 1998
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  • 81
    Digitale Medien
    Digitale Medien
    In situ FTIR spectroscopic study on crystallization process of isotactic polystyrene (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1227-1233 
    Details
    ISSN: 0887-6266
    Schlagwort(e): FTIR spectroscopy ; isotactic polystyrene ; crystallization process ; induction period ; Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The melt crystallization process of isotactic polystyrene (i-PS) was studied by means of in situ Fourier transform infrared (FTIR) spectroscopy, with a focus on the conformational changes during the induction period. The spectra obtained during the induction period suggested the occurrence of some ordered structure that is characterized by higher regularity and packing of the helical moieties than observed in the melt. This ordered structure was clearly different from the amorphous structure, and close to the crystal structure. The Avrami analysis indicated that the formation process of the ordered structure at the late stage of the induction period is similar to the growth process of the crystallites after the induction period. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1227-1233, 1998
    Zusätzliches Material: 10 Ill.
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  • 82
    Digitale Medien
    Digitale Medien
    Mechanical and dielectric properties of segmented polyurethane elastomers containing chemical crosslinks in the hard segment (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 237-251 
    Details
    ISSN: 0887-6266
    Schlagwort(e): segmented ; polyurethanes ; crosslinked ; mechanical ; dielectric properties ; Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Mechanical and dielectric properties of two series of segmented polyurethanes having soft segment concentration of 50 and 70% and a varying degree of crosslinking through the hard segment were studied. The degree of crosslinking in each series was varied by varying the butane diol/trimethylol propane ratio in the chain extender mixture. Tensile strength, elongation at break decrease, but elastic recovery increases monotonically with increasing crosslinking. The plateau modulus in the dynamic mechanical test decreases and then increases with increasing TMP content. Crosslinking causes broadening of the soft segment glass transition as seen by permittivity and loss factor measurements. It also affects high temperature behavior (above the glass transition of the hard segment); it lowers permittivity, loss factor, and ionic conductivity. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 237-251, 1998
    Zusätzliches Material: 15 Ill.
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  • 83
    Digitale Medien
    Digitale Medien
    Thermoplastic elastomer gels. I. Effects of composition and processing on morphology and gel behavior (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2379-2391 
    Details
    ISSN: 0887-6266
    Schlagwort(e): block copolymer ; thermoplastic elastomer ; physical gel ; polymer micelle ; Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Thermoplastic elastomer gels (TPEGs) composed of a poly[styrene-b-(ethylene-co-butylene)-b-styrene] triblock copolymer and a low-volatility, midblock-compatible mineral oil have been investigated at different oil concentrations to ascertain the effect of composition on TPEG morphology and mechanical properties. The impact of thermal processing is also examined by comparing gels thermally quenched to 0°C or slowly cooled to ambient temperature. Transmission electron micrographs reveal that gels with 70 to 90 wt % oil exhibit styrenic micelles measuring ca. 24 nm in diameter. Variation in composition or cooling rate does not have any perceivable effect on micelle size or shape, whereas the rate at which the gels are cooled influences the extent of microstructural order and the time to rupture (tR) at constant strain. Dynamic rheological testing confirms the presence of a physically crosslinked network at TPEG compositions ranging from 70 to 90 wt % oil, independent of cooling rate. Results presented here suggest that the dynamic elastic shear modulus (G′) scales as tαR where α varies from 0.41 to 0.59, depending on cooling rate. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. B Polym. Phys. 36: 2379-2391, 1998
    Zusätzliches Material: 12 Ill.
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  • 84
    Digitale Medien
    Digitale Medien
    General matrix formula for the weight-average molecular weights of crosslinked polymer systems (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2423-2433 
    Details
    ISSN: 0887-6266
    Schlagwort(e): gelation theory ; nonlinear polymerization ; nonrandom crosslinking ; molecular weight distribution ; Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: On the basis of the first-order Markovian statistics, we propose a general matrix formula for the weight-average molecular weight of crosslinked polymer systems, explicitly given by M̄w = M̄w,0 + WX0 (I - X)-1 Sf. This equation is valid for both step and chain-growth polymerizations, including those in a nonequilibrium state irrespective of the reactor types used. In the context of the present theory, the onset of gelation is simply stated as a point at which the largest eigenvalue of the matrix X reaches unity (i.e., det(I - X) = 0). The present theory provides a unified point of view for various types of gelling systems. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. B Polym. Phys. 36: 2423-2433, 1998
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  • 85
    Digitale Medien
    Digitale Medien
    1-Opto-thermal properties of fibers annealing effect on the birefringence variations of polyester fibers (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 555-565 
    Details
    ISSN: 0887-6266
    Schlagwort(e): polyester ; annealing ; birefringence ; mechanical loss factor ; orientation ; density ; crystalline ; profile ; Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Polyester (Egyptian) fibers were annealed at constant temperature (190°C) with different annealing times. Density, crystallinity, mean square density fluctuation, mechanical loss factor, and molecular orientation were calculated. Densities and mechanical loss factor were determined using an acoustic method. Changes in the molecular orientation were evaluated from the resulting optical data using the polarizing Pluta interference microscope. Correlation of data obtained by one method with another leads to relational changes in optothermal properties and in the molecular orientation. Changes of refractive index profiles of annealed PET fibers are provided. Illustrations using graphs and microinterferograms are shown. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 555-565, 1998
    Zusätzliches Material: 9 Ill.
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  • 86
    Digitale Medien
    Digitale Medien
    Infrared investigation of the silicon oxide phase in [perfluoro-carboxylate/sulfonate (bilayer)]/[silicon oxide] nanocomposite membranes (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 595-606 
    Details
    ISSN: 0887-6266
    Schlagwort(e): IR ; perfluoro(sulfonate/carboxylate) bilayer ; sol-gel reactions ; Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: [Perfluoro-organic]/[silicon oxide] hybrids were formed by conducting sol-gel reactions of tetraethylorthosilicate within a perfluoro(carboxylate/sulfonate) bilayer membrane in the Co+2 form. FTIR and 29Si solid-state NMR spectroscopies were used to probe general aspects of molecular structure within the silicon oxide phase as a function of its relative content. The internal gel structure is considerably unconnected in terms of the population of Si—O—Si groups in cyclic vs. linear substructures and degree of Si atom coordination about bonded SiO4 units. In situ (HO)xSiO2[1-1/4x] intrastructure become increasingly less connected and more strained with regard to bonding geometry with increasing percent silicon oxide. Structural differences are seen between the silicon oxide component incorporated in carboxylate and sulfonate layers. These inorganically modified perfluorinated ionomers have potential as fast-proton conducting membranes for fuel cells and as permselective membranes in liquid pervaporation cells. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 595-606, 1998
    Zusätzliches Material: 11 Ill.
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  • 87
    Digitale Medien
    Digitale Medien
    Construction of ternary phase diagrams in nonsolvent/solvent/PMMA systems (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 607-615 
    Details
    ISSN: 0887-6266
    Schlagwort(e): ternary phase diagram ; binodal curve ; Flory-Huggins theory ; interaction parameter ; membrane formation ; Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: In this work, the ternary phase diagrams in three nonsolvent/solvent/PMMA systems (n-hexane/n-butyl acetate/PMMA, water/acetone/PMMA, and n-hexane/acetone/PMMA) were constructed by theoretical calculation and experimental measurement. Binodal curves were calculated by using the Flory-Huggins theory for three-component systems and measured by titrating the PMMA solution with nonsolvent until the onset of turbidity. By using concentration-dependent nonsolvent/solvent and solvent/PMMA interaction parameters and constant nonsolvent/PMMA interaction parameters, good agreement has been obtained between the calculation and the measurement. The values of nonsolvent/solvent interaction parameters were taken from the literature sources, and the values of solvent/PMMA and nonsolvent/PMMA interaction parameters were measured by vapor sorption and swelling equilibrium, respectively. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 607-615, 1998
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  • 88
    Digitale Medien
    Digitale Medien
    Atomic level picture of stress relaxation in polymer melts (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 143-154 
    Details
    ISSN: 0887-6266
    Schlagwort(e): polymer simulation ; stress relaxation ; molecular dynamics ; Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: We have been developing a physical picture on the atomic level of stress relaxation in polymer melts by means of computer simulation of the process in model systems. In this article we treat a melt of freely jointed chains, each with N = 200 bonds and with excluded-volume interactions between all nonbonded atoms, that has been subjected to an initial constant-volume uniaxial extension. We consider both the stress relaxation history σ(t) based on atomic interactions, and the stress history σe(t; NR) based on subdividing the chain into segments with NR bonds each, with each segment regarded as an entropic spring. It is found that at early times σ(t) 〉 σe(t; NR) for all NR, and that, for the remainder of the simulation, there is no value of NR for which σ(t) = σe(t; NR) for an extended period; by the end of the simulation σ(t) has fallen just below the value σe(t; 50). The decay of segment orientation, 〈P2(t; NR)〉, and of bond orientation 〈P2(t; 1)〉, is computed during the simulation. It is found that the decay of the atom-based stress σ(t) is closely related to that of 〈P2(t; 1)〉. This result may be understood through the concept of steric shielding. The change in local structure of the polymer melt during relaxation is also studied. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 143-154, 1998
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  • 89
    Digitale Medien
    Digitale Medien
    The effect of concentration, temperature, and molecular weight on the dynamics of rigid-rod molecules in semi-dilute solutions (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 181-190 
    Details
    ISSN: 0887-6266
    Schlagwort(e): dynamics ; rigid-rod ; semidilute ; birefringence ; rotational diffusivity ; Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The dynamics of rigid-rod-like molecules are studied using rheo-optical techniques. Measurements of flow birefringence as a function of shear rate are utilized to understand the scaling behavior of rotational diffusivity with respect to concentration and temperature. The concentration scaling exponent increases with increasing concentration and the scaling laws are valid in narrow concentration windows. The Doi-Edwards (DE) scaling law Dr ∼ c-2, holds at very high concentrations (cL3 〉 150). The concentration scaling exponent decreases dramatically with increasing temperature at concentrations, cL2d 〉 1. Scaling of rotational diffusivity, with respect to temperature and solvent viscosity in the semidilute regime, does not follow the predictions of DE theory (and related caging ideas). On the contrary, a model proposed by Fixman was found to explain both the temperature and concentration dependence of the rotational diffusivity. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 181-190, 1998
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  • 90
    Digitale Medien
    Digitale Medien
    Structure and physical properties of segmented polyurethane elastomers containing chemical crosslinks in the hard segment (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 221-235 
    Details
    ISSN: 0887-6266
    Schlagwort(e): segmented ; polyurethanes ; crosslinked ; properties ; Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Two series of segmented polyurethanes, one containing 50% soft segments and the other with 70% soft segments were synthesized. Chemical crosslinks were introduced through the hard segment in a controlled way. Chemical polyurethane networks were characterized by swelling. The effect of the degree of crosslinking on properties was examined. It was found that chemical crosslinks in the hard segment reduce the mobility of the soft phase and destroy the crystallinity of the hard phase, but they improve heat stability of the hard domains. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 221-235, 1998
    Zusätzliches Material: 13 Ill.
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  • 91
    Digitale Medien
    Digitale Medien
    Effect of permeation temperature on permeation and separation of a benzene/cyclohexane mixture through liquid-crystalline polymer membranes (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 281-288 
    Details
    ISSN: 0887-6266
    Schlagwort(e): side-chain liquid-crystalline polymer membrane ; pervaporation ; benzene/cyclohexane mixture ; state-transformation ; benzene permselectivity ; Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: When a benzene/cyclohexane mixture of 10 wt % benzene was permeated through side-chain liquid-crystalline polymer (LCP) membranes by pervaporation at various temperatures, the permeation rate increased with increasing permeation temperature. The LCP membranes also exhibited a benzene permselectivity. The permselectivity for the benzene/cyclohexane mixture through the LCP membrane was different in the glassy, liquid-crystalline, and isotropic states. The LCP membrane had different apparent activation energies for permeation at each state. LCP membrane in the liquid-crystalline state had the highest apparent activation energy of the three states. Results suggest that the benzene permselectivity was influenced by changes in the LCP membrane structure, i.e., a state-transformation. It was found that a balance of the orientation of mesogenic groups and the flexibility of the siloxane chains was very important for benzene permselectivity. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 281-288, 1998
    Zusätzliches Material: 7 Ill.
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  • 92
    Digitale Medien
    Digitale Medien
    Dispersion polymerization of styrene in ethanol-water media: Monomer partitioning behavior and locus of polymerization (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 325-335 
    Details
    ISSN: 0887-6266
    Schlagwort(e): dispersion polymerization ; styrene ; water-ethanol mixtures ; partitioning behavior ; Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: A simulation model has been developed to predict the partitioning behavior of styrene in dispersion polymerization in ethanol-water mixtures. The composition of both the continuous phase and the dispersed phase are quantitatively estimated throughout the polymerization process. The presence of water in the system causes a considerable increase of the styrene partitioning in favor of the particles. Thus, at 70°C and for an initial composition of ethanol/water/styrene = 63.3/26.9/9.8, the concentration of styrene in the particles is about 4.8 times higher than that in the serum instead of about one in pure ethanol. The higher the polymerization temperature, the lower the styrene concentration in the particles; the higher the initial styrene concentration, the higher the styrene concentration in the particles, whereas the partition coefficient is not largely effected. In contrast, neither the interfacial tension nor the final particle size do significantly alter the simulation results. The predicted data from this model have been successfully applied to clarify the mechanisms involved in dispersion polymerization, in terms of stabilization and of kinetic events. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 325-335, 1998
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  • 93
    Digitale Medien
    Digitale Medien
    Markovian approach to nonlinear polymer formation: Free-radical polymerization with chain transfer to polymer (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 357-371 
    Details
    ISSN: 0887-6266
    Schlagwort(e): gelation theory ; nonlinear polymerization ; molecular weight distribution ; branched polymers ; polymer modification ; Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: A Markovian model is proposed for nonrandom branching reactions, by using free-radical polymerization that involves chain transfer to polymer as an example. Free-radical polymerizations are kinetically controlled; therefore, each primary polymer molecule experiences different history of branched structure formation. By assuming that the primary chains with the identical birth time conform to the same chain connection probabilities, the nonlinear structural development can be viewed as a system in which the primary chains formed at different birth times are combined into nonlinear polymers in accordance with the first-order Markov chain statistics. An explicit formula for the weight-average chain length is derived in a matrix form. The onset of gelation is simply stated as a point at which the largest eigenvalue of the transition matrix X reaches unity, i.e., det(X - I) = 0. This criterion for the onset of gelation can be considered as an extension of the Flory/Stockmayer theory to a nonequilibrium reaction system. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 357-371, 1998
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  • 94
    Digitale Medien
    Digitale Medien
    Copolymerization of hexafluoropropylene and tetrafluoroethylene: Effect on chain conformation and crystal structure (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2811-2819 
    Details
    ISSN: 0887-6266
    Schlagwort(e): PTFE/hexafluoropropylene copolymers ; crystal ; disorder ; Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: A series of new copolymers of tetrafluoroethylene (TFE) and hexafluoropropylene (HFP) containing up to 50 mol % of the hexafluoropropylene comonomer have been investigated with respect to chain conformation and crystal structure using wide-angle X-ray diffraction (WAXD). Increasing HFP content leads to significant departures from the highly ordered crystalline structure of the homopolymer PTFE; the helical conformation of the chain relaxes and untwists to accommodate the larger —CF3 pendant group in the HFP unit. Simultaneously the lateral hexagonal packing of the helices becomes less ordered and the a-dimension of the hexagonal cell increases. The above effects are progressive with increasing HFP content. At 50 mol % HFP incorporation the structure is a disordered crystalline phase. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2811-2819, 1998
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 95
    Digitale Medien
    Digitale Medien
    Nonexponentiality parameter in polymethyl(α-n-alkyl) acrylates (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2865-2868 
    Details
    ISSN: 0887-6266
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: No abstract.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 96
    Digitale Medien
    Digitale Medien
    Near infrared studies of styrene-sodium methacrylate ionomers (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2877-2886 
    Details
    ISSN: 0887-6266
    Schlagwort(e): ionomers ; NIR ; chemometrics ; Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Near Infrared (NIR) spectroscopy coupled with chemometrics techniques were utilized to study the composition and properties of styrene-sodium methacrylate ionomers. Predictive models were obtained for mol % ionic content, as well as for the ionic cluster glass transition temperature, storage modulus, and tan δ peak parameters. The results illustrate the feasibility of using NIR and chemometrics algorithms as a property predictive tool, as well as the potential for the development of full calibration models. The chemometric parameters are discussed based on correlations with ionomer NIR spectral features and the role water molecules play as a probe for the associated structure of the ionomer. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2877-2886, 1998
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 97
    Digitale Medien
    Digitale Medien
    Electrochemical fabrication of all organic heterojunction for polythiophene and its derivatives (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2905-2910 
    Details
    ISSN: 0887-6266
    Schlagwort(e): polyalkylthiophenes ; heterojunction ; BF3-diethyl ether ; electropolymerization ; Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: A new kind of all-organic heterojunction consisting of polythiophene and its derivatives was prepared by the electrochemical method in the presence of boron trifluoride diethyl ether as supporting electrolyte on indium-tin oxide glass electrode. It was observed that sequential-different oxidation potential among layers of polythiophenes is a prerequisite for the heterojunction to show rectification effect. The carrier-flow of the three semiconductors for PBrT/PT/PMT heterojunction was discussed in detail. Its rectification ratio, barrier height, and ideality factor were 392 (±2 V), 0.89 eV, and 8.1, respectively. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2905-2910, 1998
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 98
    Digitale Medien
    Digitale Medien
    Influence of associations on self-diffusion of styrene-methylmethacrylate random copolymers in semidilute acetone solution (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2931-2939 
    Details
    ISSN: 0887-6266
    Schlagwort(e): associations ; random copolymers ; self-diffusion ; Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The self-diffusion of four styrene-methylmethacrylate random copolymers dissolved in acetone, a thermodynamically bad solvent for the styrene sequences in the copolymer, were investigated by pulsed-field gradient NMR. The echo attenuations Sinc(q,t) are dominated by diffusion of clusters. At higher concentrations, physical gelation sets in (formation of a transient network), which is manifested in an anomalous, restricted diffusion at short observation times. The measured fluctuations of the positions of the chain segments in the transient network have an amplitude of about 100 nm. The free long-range diffusion attained at long observation times shows a much stronger concentration dependence than in the nonassociating solvent benzene. The results are in accord with light-scattering investigations. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2931-2939, 1998
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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  • 99
    Digitale Medien
    Digitale Medien
    Melting behavior, miscibility, and hydrogen-bonded interactions of poly(ε-caprolactone)/poly(4-hydroxystyrene-co-methoxystyrene) blends (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 95-104 
    Details
    ISSN: 0887-6266
    Schlagwort(e): blends ; melting behavior ; miscibility ; FTIR ; hydrogen bond interactions ; Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The miscibility of poly(4-hydroxystyrene-co-methoxystyrene) (HSMS) and poly(ε-caprolactone) (PCL) was investigated by differential scanning calorimetry and Fourier transform infrared spectroscopy (FTIR). HSMS/PCL blends were found to be miscible in the whole composition range by detecting only a glass transition temperature (Tg), for each composition, which could be closely described by the Fox rule. The crystallinity of PCL in the blends was dependent on the Tg of the amorphous phase. The greater the HSMS content in the blends, the lower the crystallinity. The polymer-polymer interaction parameter, χ32, was calculated from melting point depression of PCL using the Nishi-Wang equation. The negative value of χ32 obtained for HSMS/PCL blends has been compared with the value of χ32 for poly(4-hydroxystyrene) (P4HS)/PCL blends. The specific nature, quantitative analysis, and average strength of the intermolecular interactions in HSMS/PCL and P4HS/PCL blends have been determined at room temperature and in the molten state by means of Fourier transform infrared spectroscopy (FTIR) measurements. The FTIR results have been in good correlation with the thermal behavior of the blends. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 95-104, 1998
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 100
    Digitale Medien
    Digitale Medien
    A new approach for estimating the recrystallization rate and equilibrium melting temperature (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 133-141 
    Details
    ISSN: 0887-6266
    Schlagwort(e): recrystallization rate ; equilibrium melting temperature ; differential scanning calorimetry (DSC) ; poly(butylene terephthalate) (PBT) ; Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: A method is described for measuring the heat and rate of recrystallization following partial melting. The method uses a specific sequence of temperatures with a differential scanning calorimeter, and the melting and recrystallization processes were confirmed by optical observations. The method was applied to poly(butylene terephthalate). The rate of recrystallization was found to be roughly two orders of magnitude faster than isothermal crystallization from the melt. The melting temperatures obtained from recrystallization were used in the Hoffman-Weeks equation to deduce 236°C as the equilibrium melting temperature for poly(butylene terephthalate). © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 133-141, 1998
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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