COMBINED TYPE LIQUID-CRYSTALLINE POLYMERS COMPOSED OF POLY(P-PHENYLENE TEREPHTHALATE) MAIN-CHAIN AND AZOBENZENE MESOGENIC SIDE-GROUPS ATTACHED THROUGH POLYMETHYLENE SPACERS

A series of combined main chain-side group thermotropic polyesters hav ing varying lengths of oxypolymethyleneoxy spacers between the aromati c polyester main chain and the side azobenzene mesogenic unit have bee n synthesized and their liquid crystalline properties have been invest igated. The thermal and liquid crystalline (LC) properties of the poly mers were studied by differential scanning calorimetry (DSC), thermogr avimetric analysis (TGA), optical microscopy, and X-ray diffractometry . The main chain is the poly(p-phenylene terephthalate) structure, and side mesogenic groups are attached through spacers onto terephthaloyl units. The spacer length was varied from oxytrimethyleneoxy (PAZO-3) to oxyhexamethyleneoxy (PAZO-6). A polymer with a longer spacer oxydec amethyleneoxy (PAZO-10), also was included in this investigation. The polymers with spacers up to the oxyhexamethyleneoxy spacer form nemati c LC phases. In contrast, the polymer (PAZO-10) with the oxydecamethyl eneoxy spacer was found to form a layered morphology in the mesophase. Moreover, a fiber spun from PAZO-10 revealed a biaxial molecular orie ntation where the side mesogenic groups including the spacer were orie nted slightly tilted to the main chain. Other compositions produced on ly the fibers of the oriented nematic phases.