Synthesis and Characterization of Novel Combined Type Ferroelectric Liquid Crystalline Polymers Having Polyester Main Chains

Abstract

A novel synthetic route for the preparation of a new class of side chain liquid crystal (LC) polymers with an aromatic polyester main chain utilizing a diacid chloride/diol solution polycodensation is detailed in this report. Mesogenic α,β-diols, (S)-(−)-4-(((methylbutyl)oxy)carbonyl)phenyl 4‘-(((bis(6-hydroxyhexyl)methylsilyl)alkyl)oxy)biphenyl-4-carboxylate, which are composed of a long methylene spacer with a carbon−silicon−carbon linkage at the center and a side chain mesogen connected via the silicon atom, exhibited smectic A (SA) and chiral smectic C (S-C) mesophases. Molecular weights of the LC polymers of the above diols with terephthaloyl chloride and biphenyl-4,4‘-dicarbonyl chloride were found to be in the range 7000−20 000. The polymer having a terephthalic ester moiety and a hexyl spacer was found to be isotropic at room temperature. When the side chain hexyl spacer was replaced by an octyl spacer, the polymer exhibited an enantiotropic room-temperature S*C phase. When a biphenyl moiety was introduced to the main chain, instead of a phenyl group, the polymer isotropization temperature increased, suggesting a strong LC character. In this series, when the side chain spacer was hexyl and octyl, the polymers exhibited LC phases with a fine grain texture, while the polymer with a decyl spacer exhibiting a fan textured S*C phase. The latter polymer was switchable by an external electric field.