Asymmetric dimeric liquid crystals with charge transfer groups

Abstract

Two series of asymmetric dimers, the α-(4-n-butylanilinebenzylidene-4′-oxy)-ω-(4-nitroazobenzene-4′-oxy) alkanes and the α (4-dimethylaminoanilinebenzyl-idene-4′-oxy)-ω-(4-nitroazobenzene-4′-oxy)alkanes have been synthesized. Their thermal properties are compared with those of the symmetric dimers, the α,ω-bis(4-nitroazobenzene-4′-oxy)alkanes and the αω-bis(4-n-butylanilinebenzyl-idene-4′-oxy)alkanes. The asymmetric dimers exhibit a semectic A phase for which the ratio of the layer spacing to the molecular length is approximately 0.5; this is thought to imply an intercalated structure in which different parts of the molecule interleave. We propose that this structure is stabilized by a charge transfer interaction.