Polymer and Materials Science
Wiley InterScience Backfile Collection 1832-2000
Chemistry and Pharmacology
The discotic liquid-crystalline polymers poly[oxy(3,7,10,11-tetrapentoxy-2,6-triphenylenediyl)-oxycarbonyltetradecamethylenecarbonyl] (1), containing discotic mesogenic groups in the main chain and poly[methyl(3,6,7,10,11-pentapentoxy-2-triphenylenyloxyundecyl)siloxane] (2) with disc-like groups attached to the polymer chain by flexible spacers, are studied by X-ray diffraction, solid-state nuclear magnetic resonance, differential scanning calorimetry and dynamic mechanical measurements, in order to determine the dynamic and structural transitions. It is shown that low-temperature softening in both polymers is caused by the mobility of short aliphatic side chains attached to the discotic units. Once formed, the columnar mesomorphic structure is stable up to the temperature of isotropization. For the main-chain polymer, a third transition is observed in samples quenched from the melt. The transition is related to the mobility of the main chain in an amorphous structure, where the discotic units are not organized in columns.
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