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  • Artikel  (39)
  • Chemistry  (39)
  • P-4-BCMU  (1)
  • Topochemie
  • 1990-1994  (39)
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  • Artikel  (39)
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  • 1
    Digitale Medien
    Digitale Medien
    Steric effects in 3-substituted polythiophenes: comparing band gap, nonlinear optical susceptibility and conductivity of poly(3-cyclohexylthiophene) and poly(3-hexylthiophene) (1992)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 193 (1992), S. 1195-1206 
    Details
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: We present the synthesis, characterization (NMR, mass spectroscopy, IR) and polymerization of 3-cyclohexylthiophene. Although anodic polymerization is ineffective, it was possible to polymerize 3-cyclohexylthiophene with FeCI3 as the oxidizing reagent, the resulting poly(3-cyclohexylthiophene) (PC6T) having a peak molar mass of 73 000 g · mol-1. NMR-Investigations reveal that the coupling ocurred mainly via the 2,5-positions, and the band gap, as determined from UV-vis spectroscopy and cyclic voltammetry, was 2,3-2,4 eV. The nonlinear susceptibility χ(3)(-3ω; ω ω ω) of the neutral polymer and the electrical conductivity of the CIO4- and PF-6 salts were determined. The effect of the steric requirements of the cyclohexyl substituent was estimated by comparing the polymer to a poly(3-hexylthiophene) (PN6T) of the same molar mass and with a comparable number of defects (mainly head-to-head and tail-to-tail coupling of the subunits). In the case of PC6T the band gap of the neutral polymer is larger by 0,3 to 0,4 eV, the nonlinear susceptibility has approximately half the value, and the electrical conductivity of the oxidized polymer is two orders of magnitude lower than the corresponding values of PN6T. These effects are explained by the increased sterical requirements of the cyclohexyl substituent, which forces the thiophene rings out of a coplanar conformation and thus reduces the conjugation length.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1992.021930516
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  • 2
    Digitale Medien
    Digitale Medien
    Langmuir-Blodgett mono- and multilayers of preformed poly(octadecyl methacrylate)s, 1. Surface-area isotherms of atactic and isotactic poly(octadecyl methacrylate)s and transfer into multilayers (1991)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 192 (1991), S. 2203-2213 
    Details
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: In order to elucidate some of the parameters controlling the transfer of compressed monomolecular layers of preformed poly(octadecyl methacrylate)s (PODMA) onto substrates by the so-called Langmuir-Blodgett technique, an investigation was undertaken of PODMA's of different tacticity and different molecular weights. For the preparation of multilayered structures it was necessary to decrease the interaction between the side chains. This could be accomplished by introducing side chain inhomogeneities especially in the form of comonomers with shorter alkyl side chains. The transferability of a monolayer could be correlated with features in the pressure-area diagrams, as there is a liquid-analogous state formed when shorter alkyl chains are introduced; moreover a partial “melting” with lowering of the collaps pressure of the layer is seen. It appeared that with isotactic PODMA regular Y-type transferY-Type transfer: During one dipping and withdrawing cycle, two layers are transferred. Z-Type transfer: Only during withdrawing one layer is transferred. took place, whereas with the atactic polymers at the beginning a Z-type transfer occurred, gradually changing into a Y-type transfer. Applying the concept of decreasing interaction of the side chains it was possible to prepare multilayers of isotactic and atactic PODMA's.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1991.021921002
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  • 3
    Digitale Medien
    Digitale Medien
    Langmuir-Blodgett mono- and multilayers of preformed poly(octadecyl methacrylate)s, 2.Part 1: cf. ref.1 Structural studies by IR spectroscopy and small-angle X-ray scattering (1991)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 192 (1991), S. 2215-2229 
    Details
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Langmuir-Blodgett (LB) mono- and multilayers of preformed atactic and isotactic poly(octadecyl methacrylate)s were studied on gold surfaces and silicon wafers. The average orientation of the carbonyl bond of the ester group was found to be about 50° with respect to the normal to the substrate, and the side chains were concluded to be oriented perpendicular to the substrate. Furthermore, the degree of side chain orientation increased on going from a single monolayer to a multilayer. This is explained by an interdigitation of the side chains during or after the transfer process. A peculiar transfer behavior of the atactic samples is discussed in terms of the effect of disorder of the first layer on the transfer process. On heating multilayers of the polymers, melting of the crystalline domains formed by the side chains was observed at temperatures of about 35°C to 40°C. However, the layer structure appeared to be stable up to 100°C. The oriented structure was completely recovered after cooling down to room temperature.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1991.021921003
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  • 4
    Digitale Medien
    Digitale Medien
    Structural study of the aging and thermal evolution of polyiodide chains in doped trans-polyacetylene (1992)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 193 (1992), S. 853-864 
    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 evolution of the structure of iodine chains in iodine-doped polyacetylene has been followed as a function of temperature. It is shown that these chains exhibit a disorder of the second kind characterized by the lack of long-range order in chain direction. A low-temperature improvement of intra-chain order demonstrates that a substantial part of this disorder is thermal in nature. A parallel is drawn to similar effects frequently observed in crystalline iodine chain organic charge transfer salts. Furthermore, fresh samples with a nominal composition CHI0,24 are unstable under the X-ray beam. They exhibit a slow transition toward an apparently stable form corresponding to CHI0,19. The diffraction pattern in chain direction of this form can be quantitatively explained with a simple model using triiodide chains only. A comparison with other models proposed in the literature is made.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1992.021930404
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  • 5
    Digitale Medien
    Digitale Medien
    A new radical cation salt: Electrocrystallization of trans-1,2-bis(2-naphthyl)ethene and model character of the resulting salt for conducting arylenevinylene polymers (1992)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 193 (1992), S. 575-582 
    Details
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: A single-crystal radical cation salt was obtained by anodic oxidation of trans-1,2-bis-(2-naphthyl)ethene (1,2-DNE) with SbF-6 as the counter-ion. The crystal structure of (1,2-DNE)SbF6 was solved and found to be similar to the radical cation salts of unsubstituted naphthalene. The crystal structure is disordered, i.e. two orientations of the 1,2-DNE molecules are statistically occupied. The molecular overlap, resulting from these two orientations, models the structure of the salt of poly(2,6-naphthylenevinylene). In contrast to most other radical cation salts which are one-dimensional conductors, a conduction mechanism of higher dimensionality is predicted on the basis of the crystal structure of (1,2-DNE)SbF6. The identical type of disorder is also present in the crystal structure of trans-1,2-bis(1-naphthyl)ethene.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1992.021930302
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  • 6
    Digitale Medien
    Digitale Medien
    Bright field image of banded texture in lyotropic liquid crystals of a polydiacetylene (1993)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 194 (1993), S. 1289-1297 
    Details
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Formation of a banded texture was observed in thin films of a polydiacetylene prepared from the lyotropic nematic phase subject to flow. The banded texture was experimentally investigated by polarizing light microscopy and transmission electron microscopy. The banded structure is initially formed in a nematic phase of the polymer and could be imaged by TEM after its transformation to a lamellar phase which is the polymer analogon to a smectic phase in low-molecular-weight compounds. A mathematical description of the texture is given. During further relaxation of the system in the lyotropic state the initial orientation is lost by the formation of disclinations.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1993.021940503
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  • 7
    Digitale Medien
    Digitale Medien
    Soluble poly(para-phenylene)s, 3.Part 2: cf. 1. Variation of the length and the density of the solubilizing side chainsDedicated to Dr. A. Hüthig on the occasion of his 90th birthday (1990)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 191 (1990), S. 1991-2003 
    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 synthesis of a variety of alkyl-chain-substituted poly(para-phenylene) (PPP) derivatives, including those with systematically decreased density of side chains, is described, using for their preparation the Pd-catalyzed polymerization method recently developed in Mainz (Mainz route to PPP's). The degrees of polymerization achieved range between 30 and 50, allowing the synthesis of structurally well-defined and soluble PPP's with more than hundred 1,4-phenylene rings attached to each other.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1990.021910902
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  • 8
    Digitale Medien
    Digitale Medien
    A novel synthetic route to rigid-rod polyimides (1992)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 193 (1992), S. 1847-1858 
    Details
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: A new synthetic approach to soluble, rigid-rod, aromatic polymides is described. The polycondensation is done by a Pd-catalyzed aryl-aryl coupling of N,N′-bis(4-bromo-2,5-didodecyl-phenyl)-1,2:4,5-pyromellitic diimide (2) and 2,5-didodecyl-1,4-benzenediboronic acid (3). Here, the imide structure is already preformed in monomer 2. A structurally identical polymer is synthesized by the classical procedure condensing 1,2:4,5-pyromellitic dianhydride (PMDA) (4) and 4,4″-diamino-2,5,2′,5′,2″,5″-hexadodecyl-p-terphenyl (5). Both polymers are characterized in detail by 1H and 13C NMR spectroscopy, membrane osmometry and size exclusion chromatography. The average degree of polycondensation is of the order of 15. The thermal behaviour of the polymers is studied by differential scanning calorimetry and thermogravimetrical analysis.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1992.021930806
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  • 9
    Digitale Medien
    Digitale Medien
    Synthesis of silicone macrocycles having a single functional side group by hydrosilylation under high dilution (1992)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 193 (1992), S. 2929-2943 
    Details
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Macrocyclic poly(dimethylsiloxanes) (PDMS) having a single ester side group were prepared by coupling hydrosilane end-groups of telechelic PDMS and olefinic functions of methyl 3,5-diallyloxybenzoate under high-dilution conditions. The theoretical and preparative aspects of the continuous-flux technique that was used to perform the Pt-catalyzed hydrosilylation reaction were examined in the light of the results of a previous kinetic study. Excessive amounts of catalyst, or high temperature, lead to the formation of colloidal Pt, the poor chemical selectivity of which is not acceptable. When the addition reaction is performed under conditions allowing homogeneous catalysis, the reaction takes place with a steady-state concentration in reactive groups as low as 2 · 10-3-4 · 10-3 mol/L over periods as long as 24-36 h. the isolation of the monofunctional cyclic products by semi-preparative size-exclusion chromatography techniques from the linear condensation products and from more complicated multifunctional cycles is possible if the starting telechelic PDMS is of narrow molecular weight distribution.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1992.021931118
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  • 10
    Digitale Medien
    Digitale Medien
    Copolymers of ethyl p-vinylbenzenesulfonate for the preparation of polyelectrolytes of reproducible ion content (1993)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 194 (1993), S. 1237-1248 
    Details
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Ethyl p-vinylbenzenesulfonate (ESS) for which a new synthesis is described has been copolymerized with vinylcarbazole, styrene, p-methylstyrene and p-bromostyrene in N,N-dimethylformamide at 60°C using azoisobutyronitrile as initiator. Copolymer compositions and copolymerization parameters have been evaluated. Q, e-values for ESS are 4,19 and -0,11. Thermal properties of the copolymers have been investigated by differential scanning calorimetry and thermogravimetric analysis. Polyelectrolytes have been prepared either by polymer analogous hydrolysis of the sulfonic acid esters followed by conversion of the free acids into alkali metal salts or by using the alkylating properties of the esters towards tertiary amines or pyridines to form the appropriate sulfonic acid ammonium or pyridinium salts. The latter method offers the opportunity to synthesize polyelectrolytes with a well defined content of chromophores.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1993.021940417
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