COMPARISON OF THE MESOGENIC PROPERTIES OF MONOMERIC, DIMERIC, AND SIDE-CHAIN POLYMERIC LIQUID-CRYSTALS

A new series of homologous side-chain liquid-crystalline polymers based on a polystyrene, backbone has been prepared, the poly[[4-[[alpha-[(4-nitrophenyl)azo]phenyl-4'-oxy]-omega-alkyl]oxy]styrene]s. The thermal properties of these polymers have been studied, and it is shown that all members of the series exhibit a smectic phase. The thermal properties of the polymers are compared with those of the analogous monomers the 4-(alkyloxy)-4'-nitroazobenzenes, and of the dimers, the alpha,omega-bis(4-nitroazobenzene-4'-oxy)alkanes. It is found that both the clearing temperatures and the magnitude of the odd-even effect of the polymers lie between those of the monomers and dimers. We rationalize this behavior in terms of a virtual trimer model in which the backbone plays an integral role in determining the mesogenic characteristics of the polymer