Photoinitiation of MMA polymerization by thionine amine systems in the presence of SDS micelles

The photoinitiation of the polymerization of methylmethacrylate (MMA) by th e dye thionine in the presence of triethylamine and triethanolamine has bee n studied in the presence of SDS micelles, and compared with similar studie s in homogeneous methanol solutions. The conversion rates in the presence o f micelles were significantly faster than in the homogeneous solutions, and the amine concentrations at which the maximum rates were observed (similar to 0.7) were higher than in methanol (similar to 0.1). Association constan ts 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 tripl er. An expression for the concentration of the initiating radicals was dedu ced from this mechanism, and when using the experimentally determined const ants the fit to the polymerization data is quite good for amine concentrati ons 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. (C) 1999 Elsevier Science S.A. All rights reserved.