Synthesis of Block Copolymers by Combination of Atom Transfer Radical Polymerization and Visible Light Radical Photopolymerization Methods

A novel two-step procedure for the preparation of block copolymers by combination of atom transfer radical polymerization (ATRP) and visible light radical photopolymerization (VLRP) methods is described. In the first step of the procedure, omega-bromide functional polystyrene (PSt-Br) was synthesized by ATRP of styrene (St) in toluene at 110 degrees C using ethyl-2-bromopropionate and copper bromide/N,N,N',N", N''-pentamethyldiethylenetriamine as initiator and ligand, respectively. Visible light irradiation of these polymers in the presence of dimanganese decacarbonyl [Mn-2(CO)(10)] produced macroradicals at omega-chain ends capable of initiating radical polymerization of various monomers, namely methyl methacrylate (MMA), butyl acrylate (BA), and vinyl acetate (VA). In this way, depending on the termination mode of the monomer involved AB or ABA type block copolymers consisting of PSt and respective segments were readily formed. The final polymers and intermediates at various stages were characterized by H-1 NMR spectroscopy and gel permeation chromatography (GPC).