Control of particle size and carboxyl group distribution in soap-free emulsion copolymerization of methyl methacrylate–ethyl acrylate–acrylic acid

Polymer microspheres with narrow size distribution and with carboxyl groups on their surfaces were synthesized by soap-free emulsion polymerization of methyl methacrylate (MMA), ethyl acrylate (EA), and acrylic acid (AA), and the distribution of –COOH in the latex was determined by conductometric titration. Effects of ingredients on polymerization, latex particle size (D_p), and its distribution, and the distribution of –COOH were investigated. Results showed that monomer conversion and the amount of embedded –COOH (E_a) decreased, and D_p increased with increasing amounts of NH₄HCO₃. The amounts of surface –COOH (S_a) and water –COOH (F_a) and the number of –COOH on each square centimeter of the particles' surface (S_d) increased with increasing amounts of NH₄HCO₃ and AA. With the increase of initiator (APS) and AA, D_p deceased. E_a increased with the increase of AA. F_a increased and then remained constant, and S_d decreased with the increase of initiator. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 433–438, 2004