HRP-mediated polymerizations of acrylamide and sodium acrylate

Previously, we reported the horseradish peroxidase (HRP) mediated free radical polymerization of methyl methacrylate.1 The reaction medium was restricted to water/water-miscible co-solvent mixtures that solubilize both the monomer and enzyme. This paper describes HRP-mediated acrylamide polymerizations in aqueous medium with and without the addition of surfactants. Also, studies were conducted on polymerizations in concentrated emulsions using sorbitane monooleate as the surfactant. In aqueous medium, within 3 h, 98% yields of poly(acrylamide) were attained. By adding either anionic bis(2-ethylhexyl)sodium sulfosuccinate (AOT) or cationic cetyltrimethylammonium bromide (CTAB), the polymerization proceeded more rapidly so that within 60 and 75 min, respectively, 94% polymer yields were reached. When conducted in a concentrated emulsion formed with sodium monooleate, nearly quantitative yields resulted in 1.25 h. The weight average molecular weight (Mw) of the products ranged from 128 to 210 K and 106 to 154 K in aqueous medium and concentrated emulsions, respectively. In both of the above reaction systems, there was no apparent effect of the enzyme on the regulation of chain stereochemistry. The HRP-mediated polymerization of sodium acrylate conducted in aqueous medium gave poly(sodium acrylate) in yields up to 88% within 24 h with Mw ca. 119 K.