Liquid-crystalline physical gels: Self-aggregation of a gluconamide derivative in mesogenic molecules for the formation of anisotropic functional composites

Liquid-crystalline physical gels have been obtained by the self-aggregation of a gluconamide derivative through intermolecular hydrogen bonding in liq uid crystals. These liquid-crystalline gels are microphase-separated compos ites consisting of the solid fibrous aggregates of the gelling agent and th e liquid-crystalline phase of mesogenic molecules. Thermoreversible three s tates, isotropic liquid, normal (isotropic) gel, and liquid-crystalline gel , have been achieved for the mixtures of liquid crystals and the gelling ag ent. As the concentration of the gelling agent increases, the sol-gel trans ition temperature and the enthalpy change of the transition from isotropic to anisotropic increase. The increase of the enthalpy change suggests that some mesogenic molecules are anchoring strongly to the surface of the fibro us gelling agents. Variable-temperature infrared spectra show that the asso ciation and the dissociation of intermolecular hydrogen bonding of the gell ing agent occur in the process of the sol-gel transition. Liquid-crystallin e gels are responsive to electric fields in a twisted nematic (TN) cell. Th ese anisotropic gels would be applicable to new dynamically functional mate rials.