Thermal and X-ray diffraction studies of liquid crystals incorporating a perfluoroalkyl group

Abstract

Thermal properties of perfluoroalkyl 4-(4-alkoxybenzoyloxy)benzoates (1), 4-(4-alkoxyphenoxycarbonyl)benzoates (2), and 4-trans-(4-alkoxyphenoxycarbonyl)cyclohexanecarboxylates (3) have been examined, and the layer spacings of the smectic A and C phases were obtained by X-ray diffraction experiments. The perfluoroalkyl group facilitates the formation of smectic A and C phases (S_A and S_C, respectively). For compound 1, the molecular arrangements in the S_A and S_C phases are concerned with the chain length of the alkoxy group, that is the layer spacing of the S_A phase agrees with the calculated molecular length when the alkoxy group is the octyloxy group, and exceeds it when it is the butoxy one. The derivatives of compound 2 show only the S_A phase, having a somewhat interdigited arrangement. Compound 3 preferentially forms the S_A phase. The results are discussed in terms of the molecular structures and local interactions.