Incommensurability induced by intermolecular hydrogen bonding

Non-symmetric dimesogens are composed of two different mesogenic units link ed via a flexible spacer. In this study, a new type of non-symmetric dimeso gen has been built through the self-assembly via intermolecular hydrogen bo nding between appropriately designed H-bond donor (3-cholesteryloxycarbonyl pentanoic acid) and acceptor (aromatic mesogen with a pyridyl group) moieti es. As for covalently linked dimesogens, several types of smectic periodici ties are observed for these H-bonded cholesteryl compounds depending on the length of the terminal chain of the acceptor moiety: a smectic periodicity resulting from associated dimesogens is observed for long terminal chains, while short chain homologues display an intercalated structure correspondi ng to half the molecular length. The competition between these two incommen surate lengths can induce an incommensurate smectic phase where the two sme ctic periodicities coexist at long range.