Mesomorphic and Dielectric Properties of the p-n-Hexyloxybenzoic Acid-p-n-Heptyloxybenzoic Acid Liquid Crystal System

The p-n-hexyloxybenzoic acid (I)-p-n-heptyloxybenzoic acid (II) system was investigated by thermal and X-ray phase analyses and dielcometry. Solid solutions of three types were found in the low-temperature region of the system, namely, solid solution based on I ( up to 15 mol % II); solid solution based on a compound with the equimolar ratio of the components (gamma); and solid solution based on II (> 15 mol % II). The range of the two-phase equilibrium (N + I) was 2 degrees-4 degrees; a continuous nematic solution ( N) formed in the system. The temperature and composition dependences of dielectric anisotropy Delta epsilon were characterized. The gamma compound showed negative dielectric anisotropy, Delta epsilon = -1.4, which was constant over the whole temperature range of the nematic phase.