Comparison of phase situation in recently prepared chiral, racemic and achiral anticlinic high tilted compounds

Homologous series of three ring esters (biphenylates and benzoates) - chiral (S), racemic (R,S) and achiral (either isopropyl or 4-heptyl chain) were tested by DSC, X-ray and electrooptic methods. It was found that in chiral, racemic and achiral homologous series with a 4-heptyl chain, the smectic A phase is a strongly tilted phase of de Vries type, and molecules in the anticlinic phase are highly tilted within the layers (up to 45 degrees). The homologous series with an isopropyl chain gave a normal smectic A phase and low tilted synclinic or anticlinic phase. Chirality does not influence the smectic layer thickness or the molecular tilts in the smectic synclinic or anticlinic phase, but strongly influences the ability to form anticlinic order. The ability of the molecules to adopt anticlinic order is suppressed when a permanent helical structure or strong steric hindrance is absent.