Ultrasound-assisted polymerization of methyl methacrylate using the reactive surfactant Hitenol BC10 in a semicontinuous heterophase process

Semicontinuous heterophase polymerization was used to polymerize methyl methacrylate (MMA) with the reactive surfactant Hitenol BC10 (polyoxyethylene(10) alkylphenyl ether ammonium sulfate, HBC10) in the presence of ultrasound at 50 degrees C. The effects of HBC10 concentrations and the monomer addition rate (R-a) on kinetics, colloidal behavior, and molar masses were studied. Latexes with polymer content between 20 and 24 % were obtained. Particle size distributions (PSD) of latexes without HBC10 were bimodal, whereas those obtained in the presence of HBC10 were mono-modal in all cases. The average particle diameters (D-p) were in the range of 39-63 nm decreasing with the HBC10 concentration and increasing with R-a. Polymerization rates (R-p) were decreased, by increasing the HBC10 concentration, which was ascribed to chain transfer events to HBC10. It was also observed that R-p increased with R-a; however, monomer-starved conditions were favored at lower R-a values. Very high-average molecular weights were observed (1.63 x 10(6) <= M-w <= 2.34 x 10(6) g/mol) which decreased when HBC10 concentration increased, and increased with R-a. The corresponding poly-dispersity indexes (M-w/M-n) were in the range of 1.55-2.30, showing relatively wide molar masses distributions. It was observed from differential scanning calorimetry that polymers with HBC10 presented two T-g (123 and 178 degrees C) which was ascribed to HBC10 incorporated to PMMA chain, corroborated by H-1 NMR.