Graft copolymerization of 2-hydroxyethyl metacrylate onto poly(ε-caprolactone) via ATRP and investigation of its self-assembly behavior

This study aims to explore an effective route for the graft copolymerization of 2-hydroxyethyl metacrylate onto poly(ε-caprolactone) via ATRP technique and investigation of its self-assembly behavior. To aim this purpose, firstly α-bromo-ε-caprolactone, was synthesized by Baeyer–Villiger reaction and then used as a comonomer in the ring-opening polymerization of ε-caprolactone initiated with aluminum isopropoxide to produce poly(ε-caprolactone-co-α-bromo-ε-caprolactone) [P(CL-co-α-BrCL)] copolymer. The resulting copolymer was used as the macroinitiator for the controlled atom transfer radical polymerization (ATRP) of 2-hydroxyethyl metacrylate to produce a biodegradable poly(ε-caprolactone)-g-poly(2-hydroxyethyl metacrylate) [P(CL-g-HEMA)] graft copolymer. TEM images exhibited that a core-shell type nanostructure was formed with a hydrophilic outer shell and hydrophobic inner core from this copolymer. The self-assemble micelle aggregates had well defined spherical shape with a diameter of about 40 nm. The self-assembly behavior of the graft copolymer was further characterized by 1H NMR, its thermal behavior was studied by TGA and crystallization behavior was investigated by XRD and DSC.