Synthesis and photoresponsive behavior of azobenzene-containing side-chain liquid crystalline diblock polymers with polypeptide block

Well-defined azobenzene-containing side-chain liquid crystalline diblock copolymers composed of poly[6-(4-methoxy-azobenzene-4′-oxy) hexyl methacrylate] (PMMAZO) and poly(γ-benzyl-L-glutamate) (PBLG) were synthesized by click reaction from alkyne- and azide-functionalized homopolymers. The alkyne-terminated PMMAZO homopolymers were synthesized by copper-mediated atom transfer radical polymerization with a bromine-containing alkyne bifunctional initiator, and the azido-terminated PBLG homopolymers were synthesized by ring-opening polymerization of γ-benzyl-L-glutamate-N- carboxyanhydride in DMF at room temperature using an amine-containing azide initiator. The thermotropic phase behavior of PMMAZO-b-PBLG diblock copolymers in bulk were investigated using differential scanning calorimetry and polarized light microscopy. The PMMAZO-b-PBLG diblock copolymers exhibited a smectic phase and a nematic phase when the weight fraction of PMMAZO block was more than 50%. Photoisomerization behavior of PMMAZO-b-PBLG diblock copolymers and the corresponding PMMAZO homopolymers in solid film and in solution were investigated using UV-vis. In solution, trans-cis isomerization of diblock copolymers was slower than that of the corresponding PMMAZO homopolymers. These results may provide guidelines for the design of effective photoresponsive anisotropic materials. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013.