Odd–even effects in bent-core compounds containing terminal n-alkyl carboxylate groups

Abstract

A homologous series of eleven five-ring symmetrical bent-core compounds containing terminal n-alkyl carboxylate groups were synthesized, characterized and their dielectric and electro-optical properties have been investigated. The lower homologues (n = 6–11) of the series show B₂ structures with an interesting odd–even effect concerning their local director tilt and polar arrangements. This odd–even effect probably is due to steric (entropic) reasons, which are not suppressed by the relatively low polar interaction. Three of the middle homologues display a B₇′ phase, which is bistable and shows linear electro-optical switching with a transition to the chiral antiferroelectric smectic phase at a lower temperature. The higher homologues (n = 16, 18) exhibit only a B₇′ phase.