抄録
We investigated photoinduced plasticization of polymer composites containing azobenzene derivatives and nematic liquid crystals (LCs). At the initial state, a composite had a structure in which an azo-containing LC formed small domains by a phase separation from a polymer matrix and the whole composite showed glassy state and a high storage modulus over 107 Pa at room temperature. On irradiation of the composite with ultra-violet light which induces trans-cis photoisomerization of an azobenzene derivative, we observed the photochemical nematic-to-isotropic phase transition of the azo-containing LC domains. At the same time, the storage modulus and the glass transition temperature of the composites were reduced (photoinduced plasticization). In a composite with an appropriate composition, we successfully achieved glass-rubber transition by means of the photoinduced plasticization based on the photochemical phase transition of an azo-containing LC. The photoinduced plasticization of the composites would be attributed to the differences in the plasticization abilities of nematic and photochemically-induced isotropic phases of an azo-containing LC. By using the photoinduced softening of the azobenzene-functionalized composites, we have developed photoresponsive adhesives and self-healing materials.
