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

A homologous series of eleven five-ring symmetrical bent-core compounds containing terminal -alkyl carboxylate groups were synthesized, characterized and their dielectric and electro-optical properties have been investigated. The lower homologues ( = 6-11) of the series show B 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 B' 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 ( = 16, 18) exhibit only a B' phase.