Styrene-containing mesogens. Part 1: photopolymerisable nematic liquid crystals

Abstract

Several members of a novel series of styrene-containing liquid crystal monomers, based on the cyanobiphenyl mesogenic group, possess thermally stable nematic phases. These materials display a large odd–even effect, relating to the length of the flexible spacer between the styrene and cyanobiphenyl units, which is very similar to previously described liquid crystal ‘dimers’ composed of two cyanobiphenyl units. It is shown that styrene (i.e. 4-vinylphenoxy) is an excellent terminal group for cyanobiphenyl mesogens as compared to a number of other phenyloxy groups. In addition, a compatible bifunctional mesogenic crosslinker is described. Photopolymerisation of an aligned film of a low-melting eutectic mixture derived from these compounds is achieved using cationic initiation in aerobic conditions.