Abstract
The photoinitiation of the polymerization of methylmethacrylate (MMA) by the dye thionine in the presence of triethylamine and triethanolamine has been studied in the presence of SDS micelles, and compared with similar studies in homogeneous methanol solutions. The conversion rates in the presence of micelles were significantly faster than in the homogeneous solutions, and the amine concentrations at which the maximum rates were observed (∼0.7) were higher than in methanol (∼0.1). Association constants of the dye, monomer, and amines to the micelles were determined, as well as the quenching rate constants of the dye's excited states by the monomer and the amines in these systems. An overall mechanism is proposed for the production of amine free radicals which includes the postulation of a triplex. An expression for the concentration of the initiating radicals was deduced from this mechanism, and when using the experimentally determined constants the fit to the polymerization data is quite good for amine concentrations up to the maximum conversion rate. At higher amine concentrations other processes may be participating in the process decreasing the efficiency of the production of free radicals.
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