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The influence of surfactant type on monomer conversion and particle size of polystyrene particles prepared by horseradish peroxidase (HRP)-mediated miniemulsion polymerization was investigated.Miniemulsion polymerization is a versatile tool for synthesizing polymer particles. In principle, the stability of oil-in-water miniemulsions is attained by the use of a surfactant and a highly water-insoluble molecule (a so-called hydrophobe). Miniemulsions are produced by high-energy homogenization, and they usually yield stable and narrowly distributed monomer droplets; the polymerization of miniemulsions provides polymer particles of diameter 50500 nm. 1A horseradish peroxidase (HRP)-catalyzed redox system was reported to initiate vinyl polymerization of various monomers, e.g., acrylamide, 2 methyl methacrylate, 3 and styrene derivatives, 4 in which acetylacetone (ACAC) was adopted as a substrate for HRP to generate radicals in the presence of hydrogen peroxide (H 2 O 2 ). Very recently, we successfully demonstrated the preparation of polystyrene particles by enzyme-mediated miniemulsion polymerization with a polymerizable surfactant, i.e., N,N-dimethyl-N-n-dodecyl-N-2-methacryloyloxyethylammonium bromide (C 12 -DMAEMA), 5 using an HRP/H 2 O 2 /ACAC system in water.6 That report described how enzymatic miniemulsion polymerization could be used as a practical method for the preparation of relatively monodisperse polymer particles, because the approach involved a mild enzymatic process at room temperature. However, the use of surfactants other than C 12 -DMAEMA was not examined, and the role of C 12 -DMAEMA in enzymatic miniemulsion polymerization has not yet been made clear. It would be interesting to investigate the effect of surfactant type because the surfactant affects the polymerization efficiency and many performance properties of the resulting particles.In this study, the influence of the surfactant type on the enzymatic miniemulsion polymerization efficiency is discussed. Comparisons of four surfactants®anionic surfactant: sodium dodecyl sulfate (SDS), cationic surfactant: cetyltrimethylammonium bromide (CTAB), nonionic surfactant: polyoxyethylene lauryl ether (Emulgen 109P), and cationic polymerizable surfactant: C 12 -DMAEMA®were conducted for enzymatic miniemulsion polymerization (Figure 1). The effects of surfactant type on styrene conversion and particle size were investigated. To clarify the role of the surfactant in the enzymatic reaction, HRP activities in the presence of surfactants were also examined.Latexes were synthesized with SDS, CTAB, or Emulgen 109P, using the same molar amounts of surfactants as in the case of previously synthesized C 12 -DMAEMA latexes (The details of the synthetic procedure are shown in the Supporting Information.

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