The effect of lateral substitution on smectic C formation

Two related ester systems having fluoro, chloro, bromo, methyl or cyano lateral substituents have been synthesised. The effect of lateral substitution on the thermal stability of the liquid crystal phases, and particularly the smectic C phase, was examined. In some instances, a small polar group was shown to increase the stability of the smectic C phase relative to the unsubstituted analogue. The position of the lateral substituent is important. Some of the compounds exhibit a very wide smectic C phase.