The Preparation and Liquid Crystal Behaviour of Pyrimidines and Dioxans Incorporating a Dimethylene Linking Group

Abstract

The preparation of 2-(4-cyanophenylethyl)-5-alkylpyrimidines and frans-2-(4-(cyano-phenylethyl)-5-alkyl-l,3-dioxans, which incorporate a dimethylene linking group into phenylpyrimidine and phenyldioxan structures, is described. The pyrimidinyl compounds exhibit only virtual nematic-isotropic transitions and the dioxan compounds have monotropic nematic-isotropic transitions. Comparisons are made between the liquid crystal behaviour of these compounds and similar materials not incorporating the linking group. Comparisons are also made with related systems incorporating the bicyclo(2.2.2) octane ring and with systems in which the dimethylene group links two phenyl rings.

The materials described have been found to exhibit interesting dielectric properties. The pyrimidine compounds, for example, have higher perpendicular and parallel permittivities than the corresponding materials without the dimethylene linkage.