CHIRAL RADIAL PENTAYNES EXHIBITING CHOLESTERIC DISCOTIC PHASES

The synthesis of some new chiral radial pentaynes exhibiting enantiotropic cholesteric discotic (N-D*) phases at moderate temperatures is presented. By alteration of the lateral substituents we were able to obtain the phenomenon of selective reflection as well as a temperature induced helix inversion. In the latter, dilution with a nematic discotic compound has no influence on the inversion temperature, indicating that the phenomenon arises from a molecular property of the chiral compound. By adding another cholesteric radial pentayne with an almost temperature independent pitch, the inversion temperature is shifted linearly with composition in the cholesteric mixture confirming the additivity of the helical twisting power for chiral compounds in a cholesteric discotic system.