RAFT Polymerization of Dual Responsive Hyperbranched-Star Copolymers of Methacrylic Acid and Poly(Ethylene Glycol)

Smart polymers are materials that respond to external stimuli via reversible morphological changes, making them potential systems for drug delivery applications. In this study, dual-responsive star copolymers with a hyperbranched core composed of ethylene glycol dimethacrylate (EGDMA) - methacrylic acid (MAA) and poly(ethylene glycol) methyl ether methacrylate (PEGMA) arms were synthesized via two-step Reversible Addition-fragmentation Chain Transfer (RAFT) block copolymerization. The synthesis involved the formation of the hyperbranched MAA core followed by arm extension with PEGMA. The formation of the hyperbranched core and subsequent copolymerization with PEGMA were verified by FT-IR and 1H-NMR spectroscopic techniques. The distinct EGDMA peak was found at 4.3 ppm while the peak attributed to PEGMA was found at around 3.5 ppm. Furthermore, the synthesized block copolymers were both temperature and pH-responsive with LCST value at 57°C and morphological transition at pH 5.6. The synthesized smart polymer was also biocompatible based on Trypan blue cytotoxicity assay. The inherent dual responsive behavior and biocompatibility of the copolymer render it a good candidate for drug delivery systems.