Self-Assembly And Photo-Responsive Behavior Of Azobenzene-Based Copolymer

In this work, A series of azobenzene containing block copolymers were applied as building blocks to prepare aggregates via self-assembly process. Their self-assembly behaviors in selective solvent were carried out as functions of copolymer architecture and initial copolymer concentration. The photo-responsive and photo-deformation behaviors of the aggregates were well studied.(1) Self-assembly and photo-deformation behaviors of novel azobenzene copolymers poly(ethylene oxide) monomethyl ether-block-polystyrene-block-{poly[6-(4-methoxy-azobenzene-4'-oxy) hexylmethacrylate]}2 [MPEO-b-PS-b-(PMMAZO)2] were investigated. It was found that by tailoring the molecular structure and copolymer concentration, various self-assembled aggregates were obtained. At a lower concentration, all the copolymers self-assembled into simple vesicles. With increasing the polymer concentration, large compound vesicles were formed. Upon irradiation with a polarized light, the aggregates were elongated. Large compound vesicles were found to deform into compact spindles with very large axial ratio.(2) The self-assemble behavior of MPEO-b-PS-b-PMMAZO in aqueous system is studied. The influence of mixture of PS or PMMAZO is carried out. With the addition of PS homopolymer, the size of the aggregates first decrease and then increase. While the size of the hybrid micelles increases with the addition of PMMAZO homopolymer. Upon irradiation with a polarized light, the aggregates were elongated. The elongated axial ratio increase as functions of the PMMAZO and the irradiation time.(3) The self-assembly behavior and stumili-responsive properties of their aggregates in aqueous solution of poly(ethylene oxide) monomethyl ether-block-poly(acrylic aid)-block-poly[6-4-methoxy-azobenzene-4'-oxy) hexyl methacrylate] (MPEO-b-PAA-b-PMMAZO) were investigated. It was found that these copolymers can form various aggregation structures by tailing the molecular structure. The Rh of the aggregates change significantly by changing the pH value.