Reactive Surfactants in Heterophase Polymerization. 9. Optimum Surfmer Behavior in Emulsion Polymerization

In an attempt to define the conditions for the optimum use of polymerizable surfactants (surfmers), two anionic maleate surfmers were applied in various emulsion copolymerization systems including styrene/butyl acrylate/acrylic acid, vinyl acetate/VEOVA 10/acrylic acid, vinyl acetate/butyl acrylate/acrylic acid, and methyl methacrylate/butyl acrylate/vinyl acetate. It was found that the reactivity ratios were the most important variable controlling the incorporation of the surfmer into the polymer chains. The surfmer conversion also depended on the particle size: the larger the particle size, the lower the surfmer conversion. It was also found that when the surfmer copolymerized well with the monomers attaining high conversions from the beginning of the process onward, a significant part of the surfmer was buried in the particle interior, leading to unstable latexes. On the basis of the results, an optimum surfmer behavior was defined. Some preferable combinations of surfmer reactive groups and comonomers in terms of reactivity ratios were suggested. Several strategies were proposed to attain the optimum surfmer behavior, and for some of these strategies, experimental examples were given.