Facile Synthesis of Soap-Free Latexes of Methacrylic Copolymers via Sulfur-Free Reversible Addition–Fragmentation Chain Transfer Emulsion Polymerization

Conventional reversible addition–fragmentation chain transfer (RAFT) emulsion polymers contain sulfur residues and low-molar-mass surfactants that contribute to undesired odor and deleterious effects of final materials. Herein, we show how living polymer chains obtained by catalytic chain transfer polymerization of surface-active monomers allyloxy polyoxyethylene(10)nonyl ammonium sulfate and methyl methacrylate can be used as an efficient stabilizer in sulfur-free RAFT (SF-RAFT) emulsion polymerization, resulting in soap-free latexes. The reactive surfactant concentration could decrease to 0.8 wt % in the final emulsion; meanwhile, the resultant latexes show good colloidal stability with an average particle size ranging from 110 to 135 nm. Furthermore, semibatch SF-RAFT emulsion polymerization results in a well-controlled polymerization process, as evidenced by the smooth increase in molecular weight of polymer chains as the polymerization progressed. It is also apparent from the chain extension experiments that the SF-RAFT emulsion polymerization of methacrylic monomers exhibits a living characteristic.