Diblock copolymers with azobenzene side-groups and polystyrene matrix: Synthesis, characterization and photoaddressing

Diblock copolymers with a photoaddressable dispersed phase containing p-methoxy substituted azobenzene side groups and a polystyrene matrix were synthesized and characterized. The block copolymers were prepared by a sequential living anionic polymerization of butadiene and styrene. The poly(1,2-butadiene) segment was hydroborated and the hydroxy-functions converted by a polymeranalogous reaction with the azo chromophore as side groups. The block copolymers were synthesized with different compositions by varying the length of the polystyrene segment and the length of the functionalized segment in order to obtain different morphologies. In this paper, for the first time a comparison of the cis-trans photo-isomerization behavior and photoaddressing with respect to different morphologies of the block copolymers is presented. To complete the comparison, the corresponding homopolymer and a statistical copolymer were also synthesized and investigated. A different photoaddressing behavior between homopolymer, statistical copolymer and the block copolymers was observed. One principal difference and advantage for photoaddressable block copolymers is the lack of a formation of surface gratings which occurs in homopolymers and statistical copolymers.