Molecular arrangement and antiferroelectric behaviour

The crystal structures of two chiral molecules giving a antiferroelectric m esophase have been solved. These structures and some other analogs (Hori et al) present the same characteristic features: they adopt a L-shape with th eir chiral alkyl chains perpendicular to their polyaromatic cores; they pre sent smectic C-like sheets, in which contiguous molecules are antiparallel and associated through transversal dipoles (mode II type); the intersheet i nteractions between the chiral alkyl chains are quite strong. The crystal s tructure of another chiral compound giving a S-A mesophase was compared to the preceeding ones. The chiral alkyl chains are in the elongation of the c ore; contiguous molecules are parallel and associated according to a differ ent mode we named mode III; the interactions between the sheets are quite w eak.