Combining RAFT Dispersion Polymerization and Surface-Initiated ATRP for Surface Engineering of Polymeric Microspheres

We report an orthogonal polymerization strategy integrating reversible addition-fragmentation chain transfer (RAFT) polymerization and atom transfer radical polymerization (ATRP) to synthesize monodisperse surface-functional polymeric microspheres. ATRP initiator-functionalized macro-RAFT agents were employed in photoinitiated RAFT dispersion polymerization of methyl methacrylate (MMA) to yield uniform PMMA microspheres bearing ATRP initiators at the corona. Subsequent surface-initiated ATRP enabled the grafting of well-defined linear polymer chains, including poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA), poly(<i>N</i>-isopropylacrylamide) (PNIPAM), poly(<i>N</i>,<i>N</i>-dimethylacrylamide) (PDMA), and poly(poly(ethylene glycol) methyl ether methacrylate) (PPEGMA), without loss of particle uniformity. Incorporation of trithiocarbonate-containing comonomers via surface-initiated ATRP further allowed orthogonal surface-initiated RAFT polymerizations to generate graft copolymer architectures. This modular ATRP-RAFT approach affords precise control over the microsphere morphology and surface chemistry, providing a versatile platform for constructing functional polymeric microspheres for various applications.