CHIRAL RADIAL PENTAYNES EXHIBITING CHOLESTERIC DISCOTIC PHASES

The synthesis of some new chiral radial pentaynes exhibiting enantiotr opic cholesteric discotic (N-D) phases at moderate temperatures is pr esented. By alteration of the lateral substituents we were able to obt ain the phenomenon of selective reflection as well as a temperature in duced helix inversion. In the latter, dilution with a nematic discotic compound has no influence on the inversion temperature, indicating th at the phenomenon arises from a molecular property of the chiral compo und. By adding another cholesteric radial pentayne with an almost temp erature independent pitch, the inversion temperature is shifted linear ly with composition in the cholesteric mixture confirming the additivi ty of the helical twisting power for chiral compounds in a cholesteric discotic system.