Synthesis and liquid crystalline properties of trimellitimides and their sulfur analogues

A series of novel ester imides and thioimides have been synthesized from N-substituted trimellitimides and 4-hydroxybiphenyl or 4'-alkoxy-4-hydroxybiphenyls. The correlation between structure and behavior of the obtained compounds was studied. It has been found that imides without alkoxy tails are nonliquid crystalline while compounds possessing 4'-O-substituted biphenol moieties exhibit smectic phases. An introduction of sulfur atoms into an imide ring instead of oxygen atoms resulted in the fact that appropriate thioimides show monotropic SmA phases while the parent imides were nonliquid crystalline. Compounds with short aliphatic substituents (C1 - C4) show only SmA phases. The longer tails (C5) induce also SmC phases.