A redox initiating system, consisting of t-butyl hydroperoxide (tBHPO), isoascorbic acid (iAA), and ethylenediaminetetraacetic acid ferric-sodium salt (FeEDTA) was employed in emulsion polymerizations of methyl methacrylate (MMA) at high solids contents of 30 wt % in water. The system was stabilized using, linoleic acid (LA)-functionalized and nonfunctionalized surfactants based on methoxy-PEG (MPEG) and epsilon-caprolactone (CL). To optimize polymerization conditions and to avoid coagulation and solidification during the reaction, the temperature, the amount of initiator, the chemical characteristics of the surfactant, and the surfactant to monomer ratio were varied. MPEO45-CL6.5-LA (the subscripts refer to the average number of repeating monomer units) was found to be the most suitable surfactant, as it performs adequately under suboptimal reaction conditions. In the emulsion polymerization of MMA in water at similar to 30 wt %, best results were obtained at a reaction temperature of 60 degrees C, with an initiator system comprising tBHPO iAA and FeEDTA, and a surfactant to monomer ratio of 10/90 by weight or higher. Under these conditions, stable PMMA latices with average particle sizes of 200-300 nm were obtained at complete monomer conversion. (C) 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4234-4244, 2009