High intensity ultrasound initiated polymerization of butyl methacrylate in mini- and microemulsions

The polymerization of butyl methacrylate in oil-in-water emulsions stabilized by an anionic surfactant, sodium dodecylsulfate, was investigated using a chemical initiator free sonochemical polymerization technique. The effect of surfactant concentration on the rate of polymerization, the number of latex particles formed, particle diameters and the molecular weights of the polymers produced were examined. The rate of polymerization was significantly enhanced at surfactant concentration greater than 0.5 wt %. Stable latex dispersions containing nanoparticles (40-85 nm) with average polymer molecular masses of about 7 x 10⁶ g mol^-1 were obtained. The mechanism of latex particle formation is suggested to be through sonochemically produced radicals initiating polymerization of dispersed nanometer sized monomer droplets.