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  • Polymer and Materials Science  (46)
  • 2020-2024
  • 1990-1994  (37)
  • 1975-1979  (8)
  • 1970-1974  (1)
  • 1
    Digitale Medien
    Digitale Medien
    New oligomers with isatin. Condensation reactions of thiophene and 2,2′-bithiophene with isatin (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 178 (1990), S. 1-16 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Die seit langem in der Literatur als “Indophenin-Reaktion” bekannte Umsetzung von Isatin mit Thiophen wurde systematisch untersucht und auf die Umsetzung mit Bithiophen erweitert. Die Reaktionsprodukte wurden isoliert und durch FT-IR, UV, 1H-NMR, 13C-NMR sowie GPC charakterisiert.Im Gegensatz zu den Literaturdaten wurden Reaktionsprodukte mit höheren Molgewichten und anderer Molmassenverteilung gefunden. Die Reaktionsbedingungen - Lösungsmittel, Temperatur und Konzentration - sind für den Reaktionsablauf und die entstehenden Produkte von entscheidender Bedeutung.Füur die oligomeren Reaktionsprodukte werden neue Strukturen vorgeschlagen, die in Übereinstimmung mit allen analytischen Daten sind. Anhand eines Formelschemas werden die Reaktionen des Isatins mit Thiophen (Bithiophen) erläutert.
    Notizen: A systematic study of the well-known indophenin reaction between isatin and thiophene was extended to embrace bithiophene. The products of the reactions were isolated and characterized by FT-IR, UV, 1H-NMR, 13C-NMR, and GPC. The values of the thus determined molar masses and molar mass distributions differed from the data given in the literature. The reaction conditions - solvent, temperature, and concentration - are of crucial importance for the course of the reaction and the products obtained.New structures suggested for the oligomeric reaction products agree with all the analytical data. The reactions between isatin and thiophene (bithiophene) are explained schematically.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1990.051780101
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  • 2
    Digitale Medien
    Digitale Medien
    Computer simulation of hydrodynamic properties of semiflexible macromolecules: Randomly broken chains, wormlike chains, and analysis of properties of DNA (1990)
    New York : Wiley-Blackwell
    Biopolymers 29 (1990), S. 883-900 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The translational and rotational diffusion coefficients and the intrinsic viscosity of semiflexible, randomly broken, and wormilike chains have been obtained by Monte Carlo simulation in the context of the rigid-body treatment. Both approximate and rigorous rigid-body hydrodynamics are used, so that the error introduced by the approximate methods can be evaluated. A randomly broken chain and a wormilike chain having the same contour length and persistence length have the same radius of gyration but different values for any of the hydrodynamic properties. The two types of chains are compared in this regard. Considering that the cross section of the chain is represented by a cylinder better than by a string of spheres, we devise a cylindrical correction to be applied to the results simulated for chains of beads. Application is made to the analysis of experimental data for the translational and rotational coefficients of DNA fragments with up to 103 base pairs, obtaining the persistence length for each model. The values for the wormlike chain agree well with model-independent values obtained from radii of gyration and with other literature data at varying ionic strength. The randomly broken chain is equally able to reproduce the experimental length dependence of the properties, but the resulting persistence length may be too high.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360290603
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  • 3
    Digitale Medien
    Digitale Medien
    Polyene sequence distribution in degraded poly(vinyl chloride) as a function of the tacticity (1979)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 180 (1979), S. 2937-2945 
    Details
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Four fractions of poly(vinyl chloride) (PVC) having appreciably different tacticity distributions were prepared by selective extractions on samples polymerised at temperatures between +60 and -50°C. They were degraded thermally at 180°C in the solid state to conversions in the range 0,2 to 0,5% and in solution at 200°C to conversions in the range 1,6 to 5%. The polyene sequence distribution was investigated by ultra violet/visible (UV/VIS) and resonance Raman spectroscopy. The results show that the type of polyene sequence distribution depends markedly on the tacticity distribution of the polymer. Cross-linking reactions occur more readily as the syndiotacticity increases. The results are discussed and interpreted with reference to previous work relating degradation processes and tacticity.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1979.021801215
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  • 4
    Digitale Medien
    Digitale Medien
    Theoretical approach to cationic polymerization of alkenylfuranes (1990)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 191 (1990), S. 281-287 
    Details
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The molecular species proposed for the initial steps in the cationic polymerization of alkenylfurans were modeled by MNDO theoretically fully optimized structures. It was confirmed that the anomalous reactivity of ring C-5 of the monomers is determined by HOMO electron densitites, whereas calculated proton affinities from the semiempirical heats of formation fail to explain the low temperature experimental behavior of 2-vinylfuran (1c) from the point of view of stability of intermediate species. However, ab initio 4-31G calculations of proton affinities agree with the experimental facts and allow further explanations of the reactivity of furan derivatives in electrophilic media.
    Zusätzliches Material: 3 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1990.021910202
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  • 5
    Digitale Medien
    Digitale Medien
    Blends of poly(hydroxy ether of bisphenol-A) with poly(2-vinylpyridine) and poly(4-vinylpyridine) (1993)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 194 (1993), S. 501-510 
    Details
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Poly(hydroxy ether of Bisphenol-A), so-called Phenoxy resin (structure-based IUPAC name: poly[oxy(2-hydroxytrimethylene)oxy-1,4-phenyleneisopropylidene-1,4-phenylene]), is shown to be miscible with poly(4-vinylpyridine) (P4VPy, poly[1-(4-pyridyl)ethylene]) and poly(2-vinylpyridine) (P2VPy, poly[1-(2-pyridyl)ethylene]) over the entire composition range. Miscibility of the blends is evidenced by their glass transition temperatures being intermediate between the pure polymers for the blends of P4VPy and Phenoxy but being higher than the average for the case of the P2VPy/Phenoxy blends. Hydrogen bonding between the components was detected through infrared spectroscopy, which was also used in the study of mixtures of low-molecular-weight analogues, in order to calculate the free energies of mixing according to the association model of Painter and Coleman.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1993.021940213
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  • 6
    Digitale Medien
    Digitale Medien
    Acetylene-terminated amide oligomers (1993)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 194 (1993), S. 953-962 
    Details
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Six new acetylene-terminated (AT) oligomers were synthesized by reaction of 3-ethynylbenzoyl chloride and 4-ethynylbenzoyl chloride with three aromatic diamines containing four aromatic rings. The functionalization led quantitatively to AT oligomeric diamides of well defined composition, as confirmed by IR, 1H NMR and 13C NMR spectroscopy. The materials exhibited comparatively high melting points, over 200°C; thus, heating promoted curing before melting or simultaneously with melting, with the only exception of one sample that could be isolated in the amorphous state. Heating at 325°C led to insoluble cured materials, with excellent thermal resistance and glass transition temperatures Tg around 300°C.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1993.021940318
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  • 7
    Digitale Medien
    Digitale Medien
    Composites from furfuryl alcohol and inorganic solids by cationic initiation, 2Part 1: cf. ref.1.. Spectroscopic studies of poly(furfuryl alcohol)-silica composites obtained by trifluoroacetic acid initiation (1993)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 194 (1993), S. 1537-1544 
    Details
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Furfuryl alcohol polymerizes in a suspension of dispersed inorganic solids such as silica in 1,2-dichloroethane using trifluoroacetic acid as initiator. Depending on the experimental conditions the reactions load to (1) agglomeration of particles, (2) composite and soluble polymer formation, (3) composite formation. The chemical structure of the soluble polymers is not regular but the furfurylic sequence is predominant. The polymer grafted on the surface of the solid is a strongly reticulated poly(furfuryl alcohol), which also possesses conjugated double bonds that are involved in an acid-base equilibrium with trifluoroacetic acid.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1993.021940602
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  • 8
    Digitale Medien
    Digitale Medien
    Polymerization of furfuryl alcohol with trifluoroacetic acid: the influence of experimental conditions (1992)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 193 (1992), S. 1-9 
    Details
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Furfuryl alcohol was polymerized by trifluoroacetic acid in methylene chloride to give a colored polymer. This polymer possesses two main sequences in which the furan rings are connected by methylene groups (sequence 1) or by dimethylene ether groups (sequence 2). The polymer is not linear but highly branched, as detected by 1H and 13C NMR spectroscopy. Variations of the experimental conditions, such as the presence of air, the trifluoroacetic acid concentration, the reaction temperature and the solvent, do not allow a significant increase in the linear structure of the polymer. However, an increase in the acid concentration or an increase in temperature produce a decrease in the ether-bridged structure (sequences 2).
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1992.021930101
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  • 9
    Digitale Medien
    Digitale Medien
    Polymer precursor synthesis of alumina fibers (1991)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 29 (1991), S. 495-503 
    Details
    ISSN: 0887-624X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: High strength alumina fibers were fabricated with a polymer precursor process which was monitored with 13C-NMR, elemental analysis, gas evolution, SEM, and X-ray diffraction. Methylaluminoxane was chain extended by reaction with H2O, the unreacted methyl groups were converted to propanoyloxyl and i-propanoyl groups in molar ratios of 0.2 : 0.8 to 0.4 : 0.6 to afford spinning dope of adequate fluidity which can be spun into filaments with suitable stability. These precursor fibers were hydrolyzed in two stages at ambient temperatures and at 320-350°C, and then calcined at 950°C. The resulting alumina fibers have average tensile strengths up to 1.1 GPa and modulus of greater than 140 GPa.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pola.1991.080290406
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  • 10
    Digitale Medien
    Digitale Medien
    Stereoselective nucleophilic substitution of poly(vinyl chloride) with sodium thiophenate in cyclohexanone solution: Influence of the reaction temperature on the mechanism (1992)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 30 (1992), S. 99-104 
    Details
    ISSN: 0887-624X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Nucleophilic substitution of PVC with sodium thiophenate was carried out in cyclohexanone solution at 5, 25, 40, 60, and 70°C. The initial rate obeys an Arrhenius law from 25 to 60°C, with an activation energy of 70 kJ/mol. Conversion limits are observed which strongly depend on the temperature. The stereoselectivity of the reaction with respect to the configurational triads does not depend on the temperature: the distribution of configurations is only dependent on the conversion. Assuming an SN2 substitution mechanism governed by steric factors, the Monte Carlo simulation procedure described in a prior study is shown to give a good account for all temperatures above 40°C assuming for the mm, mr or rm, and rr triads a reactivity such as Rmm = 2 Rmr and Rrr nil at low temperature and very low at temperatures ≥ 40°C. The low conversion limits observed at 5 and 25°C cannot be explained by a limited accessibility of a part of the polymer. Finally, it is shown that the elimination reaction, which remains limited, does not interfere with the substitution process.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pola.1992.080300112
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