Kinetics and behavior of copolymerization in emulsion and microemulsion systems

Copolymerization of 2-ethylhexyl acrylate and acrylonitrile in emulsions an d microemulsions containing sodium dodecyl sulfate as an emulsifier was inv estigated, as a function of initiator concentration, temperature, monomer-f eed composition, and surfactant concentration. The emulsions were observed to turn into transparent/translucent and stable latexes, mimicking the prop erties of true microemulsion latexes, on polymerization. The rate of emulsi on polymerization was found to be faster than that of the microemulsion pol ymerization. The rate of polymerization, percentage conversion, and final n umber of latex particles were found to be a function of initiator concentra tion, reaction temperature, and acrylonitrile concentration in feed. The ra te of polymerization showed a dependency of -0.05 power of the surfactant c oncentration in the area covering emulsion and microemulsion regions. Intri nsic viscosity values showed that the products from true microemulsion poly merization were of higher molecular weight than those from "emulsion-to-mic roemulsion" The decrease in the particle size with conversion in emulsion p olymerization was attributed to the role of the coemulsifier 2-ethylhexyl a crylate and engulfing of the initial polymerization system by the local hea t production during polymerization.