Ambient temperature living radical copolymerization of styrene and methyl methacrylate with sodium hypophosphite as reducing agent

A facile, safe and economical reducing agent, sodium hypophosphite (NaH2PO2 center dot H2O), has been successfully employed for ambient temperature living radical copolymerization of styrene (St) and methyl methacrylate (MMA). Such effective reducing agent significantly improved the reactivity of low reactive St monomers during the copolymerization, where the reactivity ratios of St and MMA were determined to be 0.50 and 0.36 by Finemann-Ross method. Thus the copolymerizations proceeded fast and showed typical living/controlled features, as evidenced by pseudo first-order kinetics of polymerization, linear increase in molecular weight versus monomer conversion, and low polydispersity index values. Effects of the concentration of reducing agent and the monomer feed ratio on the copolymerization were investigated in detail. Furthermore, gel permeation chromatography and H-1-NMR analyses as well as chain extension experiments confirmed the high chain-end functionality of the resultant copolymer.