Modular photoinduced grafting onto approach by ketene chemistry

A modular approach for the synthesis of graft copolymers by the combination of reversible addition–fragmentation chain-transfer (RAFT) polymerization and photoinduced acylation processes is described. In the two-step approach, first the copolymers of benzodioxinone containing monomer, namely, 4-oxo-2,2-diphenyl-4H-benzo[d][1,3]dioxin-7-yl methacrylate (BDMA) and methyl methacrylate (MMA) in different feed ratios were prepared by RAFT polymerization. In the subsequent step, dichloromethane solutions of these copolymers (PMMA-co-PBDMA) were irradiated at λ = 300 nm in the presence of independently prepared hydroxyl functional polymers such as poly(ethylene glycol) (MeO-PEG-OH) and poly(ɛ-caprolactone) (PCL-OH). Side-chain esterification reaction between photochemically generated ketene groups and hydroxyl functionalities resulted in the formation graft copolymers. The intermediates and final graft copolymers were characterized by ¹H NMR, UV, IR, fluorescence, and GPC measurements. The success of the process was also confirmed by a model reaction using pyrene methanol.