Stabilization of Aqueous MMA Emulsions Using Mixtures of Surfactants and Implications on MMA Miniemulsion Polymerizations

摘要

Miniemulsion polymerization is a robust and simple method for manufacture of polymer nanoparticles. However, it is strongly dependent on the precursor monomer-in-water emulsion stability. Thus, the present study investigates the influence of concentration and combination of nonionic surfactants (resulting in different hydrophile–lipophile balances, HLB) on the stabilization of emulsions of methyl methacrylate in water. Backscattering profiles obtained with Turbiscan show that a combination of Tween80 and Span80 can grant the desired initial system stabilization, although the optimum HLB values depend on the amount of surfactant mixture. Miniemulsion polymerizations are then successfully performed with nonionic surfactant mixtures, providing high monomer conversion in less than 1 h and poly(methyl methacrylate) nanoparticles with average diameters ranging from 300 to 500 nm. Finally, it is observed that the addition of small amounts of an anionic surfactant to the surfactant mixture (10 wt.) can be very beneficial for the process, allowing the control of reaction rates, the production of smaller nanoparticles with average diameters from 100 to 300 nm, and the enhanced stabilization of the final solid dispersion, while simultaneously keeping the concentration of ionic surfactants small.