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 (SA and SC, respectively). For compound 1, the molecular arrangements in the SA and SC phases are concerned with the chain length of the alkoxy group, that is the layer spacing of the SA 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 SA phase, having a somewhat interdigited arrangement. Compound 3 preferentially forms the SA phase. The results are discussed in terms of the molecular structures and local interactions.