EMULSION COPOLYMERIZATION AND TERPOLYMERIZATION OF STYRENE, METHYL-METHACRYLATE, AND METHYL ACRYLATE .1. EXPERIMENTAL-DETERMINATION AND MODEL PREDICTION OF COMPOSITION DRIFT AND MICROSTRUCTURE IN BATCH REACTIONS

Part I of this series the reactivity ratios of the comonomer pair meth yl acrylate-methyl methacrylate were determined with low-conversion bu lk polymerizations. It was shown that the binary reactivity ratios of the systems styrene-methyl acrylate, styrene-methyl methacrylate, and methyl acrylate-methyl methacrylate describe composition drift in low- conversion bulk terpolymerizations with these monomers reasonably well . A computer model was developed to simulate the composition drift in emulsion co- and terpolymerizations. The composition drift in two batc h emulsion copolymerization systems (styrene-methyl acrylate and methy l acrylate-methyl methacrylate) and one emulsion terpolymerization sys tem (styrene-methyl acrylate-methyl methacrylate) was investigated bot h experimentally and with the model. Experimental results were compare d with model calculations. The copolymer chemical composition distribu tions (CCD) were determined with gradient polymer elution chromatograp hy (GPEC(R)). This technique was also used for the first time to obtai n information about the extent of composition drift in emulsion terpol ymerizations. Cumulative terpolymer compositions were determined with H-1-NMR as a function of conversion and with this information the thre e-dimensional CCD was obtained. The composition drift was analyzed wit h respect to free radical copolymerization kinetics (reactivity ratios ) and monomer partitioning. It was shown that in most emulsion copolym erizations the composition drift is mainly determined by the reactivit y of the monomers and to a lesser extent by monomer partitioning, exce pt in systems where there is a large difference in water solubility. T he model predictions for cumulative terpolymer composition as a functi on of conversion and the three-dimensional terpolymer CCD showed excel lent agreement with the experiments. The GPEC(R) elution chromatogram of the terpolymer was found to be in accordance with the predicted CCD and the experimentally determined CCD. (C) 1996 John Wiley & Sons, In c.