title: Horseradish peroxidase mediated free radical polymerization of methyl methacrylate.
abstract: This paper reports the free radical polymerization of methyl methacrylate (MMA) catalyzed by horseradish peroxidase (HRP). A novel method was developed whereby MMA polymerization can be carried out at ambient temperatures in the presence of low concentrations of hydrogen peroxide and 2,4-pentanedione in a mixture of water and a water-miscible solvent. Polymers of MMA formed were highly stereoregular with predominantly syndiotactic sequences (syn-dyad fractions from 0.82 to 0.87). Analyses of the chloroform-soluble fraction of syndio-PMMA products by GPC showed that they have number-average molecular weights, Mn, that range from 7500 to 75,000. By using 25% v/v of the cosolvents dioxane, tetrahydrofuran, acetone, and dimethylformamide, 85, 45, 7 and 2% product yields, respectively, resulted after 24 h. Increasing the proportion of dioxane to water from 1:3 to 1:1 and 3:1 resulted in a decrease in polymer yield from 45 to 38 and 7%, respectively. Increase in the enzyme concentration from 70 to 80 and 90 mg/mL resulted in increased reaction kinetics. By adjustment of the molar ratio of 2,4-pentanedione to hydrogen peroxide between 1.30:1.0 and 1.45:1.0, the product yields and Mn values were increased. On the basis of the catalytic properties of HRP and studies herein, we believe that the keto-enoxy radicals from 2,4-pentanedione are the first radical species generated. Then, initiation may take place through this radical or by the radical transfer to another molecule.
authors.affiliation: Polytechnic University, NSF Center for Biocatalysis and Bioprocessing, Six Metrotech Center, Brooklyn, New York 11201, USA.
authors.forename: B
authors.initials: B
authors.lastname: Kalra
authors.forename: R A
authors.initials: RA
authors.lastname: Gross
mesh_terms: D005609:Free Radicals / Q000737:chemistry*; D006735:Horseradish Peroxidase / Q000737:chemistry*; D006861:Hydrogen Peroxide / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D019904:Polymethyl Methacrylate / Q000737:chemistry*; D012997:Solvents; D013696:Temperature
chemical_list: D005609:Free Radicals; D012997:Solvents; D019904:Polymethyl Methacrylate; D006861:Hydrogen Peroxide; D006735:Horseradish Peroxidase