A LASER LIGHT SCATTERING STUDY OF THE KINETICS OF THE EMULSION POLYMERIZATION OF METHYL METHACRYLATE IN AQUEOUS MEDIUM

Date of Completion

January 1981

Keywords

Chemistry, Polymer

Degree

Ph.D.

Abstract

This is an investigation of the kinetics of the earliest stages of the emulsion polymerization of Methyl Methacrylate in aqueous medium. The study is a continuation of earlier work done by Fitch, Tsai, Watson, Bakker-Ruszala and others, and attempts to further clarify the mechanism of particle formation in homogeneous systems.^ For the experiments the monomer concentration was varied below the point of saturation. Other variables were initiator and stabilizer concentration. Sodium dodecyl sulfate was used as stablizer, and the photodegradable compound biacetyl was used as initiator. The experiments were carried out under continuous illumination from a Hg-vapor initiating light source.^ A modified Brice-Phoenix 2000 DM light scattering photometer was used for the in situ detection of the polymerization process. A He/Ne laser was employed as the scattering light source allowing for high signal stability. The signals were detected simultaneously at two photomultiplier tubes, one at 0(DEGREES) and the other at 90(DEGREES) to the laser beam. The differential signal was subsequently recorded. Thus external noise could be minimized by subtraction. The differential signal was recorded as a function of time, and converted to Rayleigh ratios. Theoretical computations based on the Hansen-Ugelstad theory were carried out for comparison.^ The results indicate that capture and coagulation can be ruled out during the first few seconds of polymerization. It was also clearly shown that coagulation plays an important role later in the process. Evidence was also found for what could be called a binary solvent effect, where a higher monomer to water ratio would result in a higher solubility of the oligomeric chains, thus allowing oligomers to grow longer the higher the monomer concentration. ^

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