Effect of additives on the initial stage of emulsion polymerization of methyl methacrylate using polyvinyl alcohol as a protective colloid

Model experiment of emulsion polymerization of methyl methacrylate was carr ied out at a diluted monomer concentration of 1%, in the presence of 1% pol yvinyl alcohol based on water as a protective colloid using ammonium persul fate as an initiator. The polymerization proceeded smoothly yielding stable emulsion with about 80 nm particle size. Fractionation of the polymers in the emulsion revealed that 90% of polymethyl methacrylate and 60% of polyvi nyl alcohol were grafted. Addition of alcohols such as isopropyl alcohol to the system decreased the grafting to a great extent, resulting in the incr ease in the particle size. This was attributed to the decrease in hydrogen abstraction reaction from polyvinyl alcohol with sulfate radical, due to th e competing hydrogen abstraction reaction from low molecular weight alcohol .