Photo-tunable multi-arm star azobenzene side-chain polymer with hyperbranched polyether core

A hyperbranched polymer containing azo chromophore groups on the periphery has been successfully synthesized by atom transfer radical polymerization using hyperbranched polyester bearing peripheral bromoacetyl groups as the initiator and 4-[(E)-phenyldiazenyl]phenyl acrylate as monomer and CuBr/2,2′-bipyridine (bpy) as the catalyst. The resultant products were characterized by FT-IR, NMR, TEM, and EA. The photo-tunable azobenzene-functionalized hyperbranched polymer as well as the corresponding azo monomer showed photoresponsive behavior of the azobenzene type molecules. UV–vis spectra of the azobenzene-functionalized hyperbranched polymer in tetrahydrofuran showed isomerization of azobenzene units upon irradiation with UV (365 nm).