Photoinduced Reversible Semicrystalline-to-Amorphous State Transitions of Stereoregular Azopolyesters.

We report the synthesis of isotactic azobenzene-based polyesters (azopolyesters) with main-chain chirality via highly enantioselective resolution copolymerization of racemic azobenzene-containing epoxides with cyclic anhydrides. All polyesters with trans-azobenzene moieties were found to be semicrystalline materials with melting temperatures of 153-231 °C, while the corresponding isotactic cis-azopolyesters were amorphous. The azobenzene groups in the copolymers exhibited reversible trans-to-cis and cis-to-trans photoisomerization upon irradiation with light.