Ferroelectric and antiferroelectric liquid crystals of chiral swallow-tailed materials with an ester group linked to achiral alkyl chains

Abstract

Two homologous series of chiral materials, 3-pentyl (S)-2-{6-[4-(4′-alkanoyloxyphenyl)benzoyloxy]-2-napthyl}propionate, PmPBNP(m=7-11), and 2-ethyl-1-butyl (S)-2-{6-[4-(4′-alkanoyloxyphenyl)benzoyloxy]2-napthyl}propionate, EBmPBNP(m=7-11), derived from a chiral moiety, (S)-2-(6-methoxynaphthyl-2)propionic acid, in conjugation with swallow-tailed groups attached to the external side of the chiral centre, have been synthesized and their mesomorphic phases studied. Members of the PmPBNP series, with the exception of P7PBNP and P8PBNP, showed an enantiotropic antiferroelectric SmC*_A whereas, members of the EBmPBNP series, with the exception of EB7PBNP, showed an enantiotropic ferroelectric SmC*_A phase. The maximum spontaneous polarization for these materials was in the range 20–60 nC cm⁻². The electro-optic responses measured for both series of materials in ferroelectric and antiferroelectric phases displayed thresholdless V-shaped switching.