SYNTHESIS AND PROPERTIES OF COMB-LIKE LIQUID-CRYSTALLINE POLYMERS WITH ELECTROOPTICALLY ACTIVE MESOGENIC SIDE-GROUPS

A system of non-centrosymmetric mesogens (4, nitrobenzylidene-2'-methy lphenol(M2) and 4, cyanobenzylidene-2'-methylphenol(M5)) and their cor responding alkanol phenoxy ethers (M2C8 and M5C8) was investigated. Th e mesomorphic properties of mixtures of these low molecular mass compo unds were established. The properties of home and random copolymers of M2 and M5 attached as side-groups via a C8 spacer to a poly(methyl me thacrylate) backbone were studied. A phase diagram was obtained. The t hermo-mechanical relaxation properties of this system were also invest igated by means of thermostimulated currents. While monotropic namatic mesophases dominate the low molecular mass M2C8-M5C8 system, the copo lymers display an enantiotropic nematic behaviour. Two relaxation proc esses dominate the thermomechanical response of this copolymer system. One is interpreted as related to the segmental motion of the backbone (alpha-peak), the second, to the motion of the mesogenic groups (delt a-peak). While the parameters related to the alpha peak relaxation suc h as the activation energy or relaxation times are not strongly affect ed by copolymer composition, the delta relaxation is affected by the c omposition of the copolymer.