Thermotropic liquid-crystalline main-chain viologen polymers: homopolymer of 4,4'-bipyridyl with the ditosylate of 2,5-hexanediol and its copolymers with the ditosylate of 1,10-decanediol

摘要

The 1,1'-dialkyl-4,4'-bipyridinium salt is usually known as viologen. This moiety can be incorporated either along the backbone of the polymer chain or as pendent group attached to a polymer chain, resulting in main-chain and side-chain viologen polymers, respectively. The liquid crystallinities, that is, both the thermotropic and lyotropic properties of viologen polymers have received considerable attention in the field of ionic liquid-crystalline polymers. Bhowmik et al. as well as others reported that the main-chain viologen polymers are an amphotropic class of polymers. They are usually prepared by the Menshutkin reaction of 4,4'-bipyridyl with α,ω-methylene ditosylate in acetonitrile. They exhibit smectic phases at their T_m values and have smectic-to-isotropic transition (T_i) values, which are well below their decomposition temperatures.