Polymeric ferroelectric liquid crystals with a 2-methylalkanoyl group-effect of substitution in the core benzene ring

Abstract

Polymeric ferroelectric liquid crystals with a 2-methylalkanoyl group in their mesogenic side chains exhibit large spontaneous polarization and are expected to respond quickly to an electric field. We prepared and examined novel polymeric liquid crystals. They contained a 2-methylbutanoyl or a 2-methyloctanoyl group, in which the ortho position to the alkanoyl group on the core was replaced by a fluorine atom, a hydroxy group, or a methyl group. We studied the effect of the substitutions on their properties and found that they lower the clearing points. The low spontaneous polarizaion of the polymer that underwent the fluorine substitution can be explained by the electronegativity of the fluorine atom. IR analysis verified that the substituted hydroxy group formed an intramolecular hydrogen bond with the adjacent alkanoyl carbonyl group. The steric hindrance introduced by the methyl substitution increased the tilt angle and slightly increased the intermolecular distance between the mesogens.