Liquid‐crystal behaviour of some laterally substituted stiffchain polyesters containing 2‐phenylbenzoxazole units

摘要

AbstractThe synthesis and the phase behaviour of three laterally substituted stiff‐chain polymers containing 2‐phenylbenzoxazole units is reported. Polymers were obtained by reaction of 2‐(4‐acetoxyphenyl)‐6‐acetoxybenzoxazole with 2‐phenoxyterephthalic acid (polymer2a), 2‐phenylthioterephthalic acid (polymer2b) and 2‐hexadecylthioterephthalic acid (polymer2c). Polymers2aand2bare virtually non‐crystalline.2ais nematogenic, while for2ba smectic‐like liquidcrystal phase is observed, whose structural periodicity is probably connected with the intercalated stacking of the lateral phenyl groups along the direction of the chain axes. The solid phase of2cis of the sanidic type. On melting, a liquid‐crystal phase with equatorial periodicity is observed. This periodicity is probably related to the segregation of the stiff chains betwee