SYNTHESIS AND CHARACTERIZATION OF NOVEL SIDE-CHAIN LIQUID-CRYSTALLINEPOLYCARBONATES .3. DYNAMIC-MECHANICAL ANALYSIS OF THE SECONDARY RELAXATION PROCESSES

The dynamic mechanical properties of two homologous series of sidechai n liquid crystalline polycarbonates were studied. One series with oxyn itro-stilbene mesogenic groups and alkyl spacers of different lengths and another series with phenyl benzoate mesogenic groups with alkoxy t ails of different lengths. The influence of spacer length and tail len gth on the low temperature relaxation processes was investigated. For the polymer with an undecyl spacer also the influence of side group cr ystallinity on the secondary relaxations was analyzed. A gamma-relaxat ion could be ascribed to motions of either the spacer or the alkoxy ta il. Three different beta-relaxations could be ascribed to the carbonat e groups in the backbone and to the mesogenic groups in the frozen liq uid crystalline state and in the crystalline state, respectively. The alpha-relaxation, corresponding to the glass transition, showed a stro ng shift to lower temperatures with increasing spacer length but was h ardly influenced by the tail length.