Abstract
Spirobicromane (SPI) are supposed to have a drastic influence on the mesomorphism due to their rigid, bent geometry and bulkiness; therefore, we attempted to build the SPI unit into conventional thermotropic polyester and examine its effect on mesomorphism. In this study, thermotropic copolyester series I and II, with their SPI moieties aggregated or evenly distributed in the polymer chain, can be prepared according to single- and two-step polycondensation reactions of different amounts of SPI, 1,7-heptanediol (HD), and terephthaloyl bis(4-oxybenzoyl chloride) (TOBC), respectively. Thermal transition temperatures (Tm and Ti) for both copolyester I and II series decreased with the increasing SPI moieties incorporated and no liquid crystalline properties were observed for copolyesters with SPI content more than 20mol%. With more aggregated SPI moieties in the chain, copolyester I series possess higher isotropization temperature and better smectic order as compared to copolyesters II of the same composition, in which the detrimental SPI moieties are assumed to be evenly distributed to efficiently prevent an ordered chain packing in the mesomorphic state.
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