Material design for polymer/azobenzene liquid crystal/metal salt composite films possessing thermo‐ and photoresponsive ionic conductivity

Various azobenzene derivatives and polymers were attempted as materials for thin composite films containing a polymer, a liquid crystal, and lithium perchlorate which can undergo ionic-conductivity switching induced by light or heat. Poly(vinyl chloride) -based composite films containing enantiotropic azobenzene liquid crystals 1, exhibited significant ionicconductivity change based on thermo- and photoinduced phase transitions of 1, the temperature dependence on the ionic conductivity reflecting the enantiotropic phase transition behavior of the liquid crystals. Marked, reversible ionic-conductivity switching on alternating irradiation of UV and visible lights was attained with the composite films containing 1, especially 1 (n = 12). Incorporation of monotropic liquid crystals 3 to the composite films allowed bistability in the temperature dependence on the ionic conductivity. Employment of a polycarbonate resin and poly(methyl methacrylate) as the polymer material of the composite films gave similar ionic-conductivity changes to the poly(vinyl chloride) composite films, whereas polyethyleneoxide brought about some different results in the photoinduced ionic-conductivity change.