I. Investigation of occlusion phenomena in free radical vinyl monomer lymerization. II. Development of turbidimetric titration as a rapid method of complex polymer system analysis



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An investigation of the heterogeneous solution polymerization of methyl methacrylate resulted in the correlation of the rate of polymerization and molecular weight of the polymer product with the differences in hildebrand solubility parameters between the precipitating polymer and the reaction medium. This work was extended into a study of the effects of the initial heterogeneous solution polymerization conditions on the ability of the precipitated polymer to occlude macroradicals. This ability to occlude macroradicals was determined by the subsequent formation of a block copolymer on the addition of a different second monomer. Emulsion polymerization was used to produce shell-core polymer particles with unique solubility properties. The emulsion polymerizations of styrene and methyl methacrylate were modified to give increased rates of polymerization by a reduction in the rate of termination. This was accomplished by adding a suitable nonreactive solvent to the monomer which is a poor solvent for the resulting polymer. A correlation, similar to that observed in heterogeneous solution polymerization, was found between the solubility parameter of the nonreactive solvent and the rate of polymerization of the emulsion system. Turbidimetric titration was used as an analytical technique for the separation of complex copolymer systems. It was found that low polymer concentrations (i.e. less than 1.0 mg/100 ml) greatly increased the effectiveness of the technique. Apparatus was designed and constructed which allowed these low concentrations to be used routinely.