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  • Polymer and Materials Science  (3)
Datenquelle
Materialart
Erscheinungszeitraum
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  • 1
    Digitale Medien
    Digitale Medien
    Molecular order in a homlogous series of liquid-crystalline side group polymers from multidimensional carbon-13 and silicon-29 NMR spectroscopy (1994)
    Weinheim : Wiley-Blackwell
    Acta Polymerica 45 (1994), S. 204-209 
    Details
    ISSN: 0323-7648
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The variation in the degree of orientational order as a function of molecular site is investigated in a homologous series of liquid-crystalline side group polymers based on a polysiloxane backbone using multidimensional carbon-13 and silicon-29 NMR spectroscopy. Significant differences in ordering behavior are observed amongst the members of the series as the length of the flexible spacer group is increased. In particular the degree of order on the polymer backbone and the size of the order gradient away from the aligned mesogen are correlated with the parity of the spacer chain.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/actp.1994.010450311
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  • 2
    Digitale Medien
    Digitale Medien
    Local motions in polymeric and low molar mass supramolecular hydrogen bond assemblies: One- and two-dimensional 2H-NMR studies, full papers (1995)
    Weinheim : Wiley-Blackwell
    Acta Polymerica 46 (1995), S. 291-299 
    Details
    ISSN: 0323-7648
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Supramolecular structures based on 4-(3,5-dioxo-1,2,4-triazolidin-4-yl) benzoic acid (U4A) units act as effective junction zones in functionalized polybutadienes, resulting in the formation of thermoplastic elastomers. The dynamics on a molecular scale of the phenyl rings have been probed by 2H-NMR. In the polymeric system, there are three spatially separated environments, which are reflected in the mobility of the polar units. Phenyl rings which are incorporated in the structures are either rigid or undergo 180° phenyl flips. The small fraction of free functional groups move isotropically and their mobility is coupled to the dynamics of the polybutadiene matrix. In two model compounds, where the polymer backbone is replaced by a 1-butenyl (tBu-dU4A) or a C12H24-chain (C12-dU4A), the packing of the single molecules is more perfect, resulting in better-defined dynamics of the molecules. The one-dimensional 2H-NMR spectra can be described quantitatively assuming a distribution of correlation times over 3 decades for the C12-dU4A and 2 decades for the tBu-dU4A, respectively. From the average jump rates the activation energies are determined as 101 kJ/mol and 102 kJ/mol. The geometry of the motional processes is defined by the environment in the clusters up to the order-disorder transition temperature as determined by DSC. The two-dimensional spectra of the model compounds show an elliptical exchange pattern, indicating well-defined slow 180° phenyl flips on a time scale of 100 ms up to 3 s.
    Zusätzliches Material: 15 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/actp.1995.010460402
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  • 3
    Digitale Medien
    Digitale Medien
    Influence of a brushed polyimide surface on photoinduced reorientation processes in dye-containing liquid crystalline polymers (1996)
    Weinheim : Wiley-Blackwell
    Acta Polymerica 47 (1996), S. 35-39 
    Details
    ISSN: 0323-7648
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Infrared spectroscopy is used to study the influence of the polarization of the irradiating light and the substrate surface treated with polyimide on the reorientation process of dye-containing liquid-crystalline side-group copolymers. The depolarization of the linearly polarized light on brushed polyimide surfaces affects the reorientation process and as a consequence the irradiation direction becomes the new order axis after irradiation. Relaxation processes are observed after short irradiation times, since a new stable equilibrium state has not been reached. In contrast, complete reorientation, achieving changes in order parameter of 0.9, is observed after long irradiation times. The system is then stabilized in the new orientational distribution and no relaxation processes occur. The relaxation processes can be explained by a combination of matrix response and thermal cis-trans back relaxation of the azobenzene.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/actp.1996.010470105
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