The effect of the terminal trifluoromethyl group on nematic liquid crystal thermal stability

Abstract

The introduction of a terminal substituent into the molecule of a compound capable of forming liquid crystals enhances the clearing temperature of the nematic phase relative to that of the unsubstituted analogue. The efficiency of the trifluoromethyl group in this respect is assessed relative to that of other groups by incorporating the group in two Schiff's bases. No enantiotropic nematic phase was produced in either case, and ‘virtual’ transition temperatures had to be obtained. The low efficiency of the CF₃ group relative to that of other groups is discussed.