Linear, Y-shaped, and H-shaped amphiphilic azobenzene copolymers: Facile synthesis and topological effect on self-assembly and photoresponsive property

Abstract

Novel linear (AB-type), Y-shaped (AB2-type), and H-shaped (B2AB2-type) amphiphilic block copolymers of poly(ethylene glycol) (PEG) with polymer containing azobenzene chromophores (PAzo) were successfully synthesized by the head-to-tail acyclic diene metathesis (ADMET) polymerization. Three types of acrylate functional ADMET chain stoppers were first prepared through the Michael addition reaction and esterification. Then, a series of amphiphilic copolymers were obtained via through ADMET polymerization of azobenzene-functionalized asymmetric α,ω-diene monomer using the as-prepared PEGs with acrylate end groups as macromolecular chain stoppers. Finally, the amphiphilic copolymers could spontaneously self-assemble into spherical nanoparticles in an aqueous medium. In view of the photoresponsive blocks of PAzo, the solution photochemical properties of the solution and the sizes of these spherical aggregates can be manipulated by changing the parameters such as UV and visible lights. The differences in structure of the copolymers induced profound effects on photoresponsive performance.