Synthesis and Liquid Crystal Formation of Ionic Polymers Having Hydrophobic Side-Chains

Thermotropic ionic liquid crystal polymers were synthesized by ion complexation of polyacrylic acid and low-molecular-weight amines with hydrophobic chains. The ionic liquid crystal polymers obtained in this research clearly exhibited a thermotropic liquid-crystalline phase on the heating and cooling processes. The ionic liquid crystal polymers (PA/N-6-n) consisting of polyacrylate ions and cationic mesogens with an azobenzene core induced a smectic A phase. The thermal stability of the smectic A orientational structure in PA/N-6-n depended on a terminal group of the cationic mesogen. Moreover, the ionic liquid crystal polymers composed of the polyacrylate ions and ammoniums with long alkyl chains (without mesogenic cores) also revealed the smectic A phase. These results for the liquid crystal formation of the ionic liquid crystal polymers indicate that the ionic interaction acts effectively in producing the liquid-crystalline state through an ionic aggregation.