Manfred Gordon

Electron microscopic study of the locus of a latex reaction

Abstract The outstanding example of the study of reaction loci in an emulsion system is Harkinss work in the field of emulsion polymerization. A simpler case presents itself for study when chemical reactions are carried out with preformed polymer emulsions (latexes), as in the hydrochlorination of polyisoprene latex. Here the reaction consists in the progressive conversion of the individual unsaturated isoprene units to their hydrochlorinated form: (see PDF for diagram) the polymer particles preserving their identity throughout the reaction. The hydrochloric acid arrives at the site of reaction by a series of diffusion processes from the vapor phase and through the continuous aqueous phase. In principle there are still two loci at which the isoprene units may react with this reagent: in the bulk of the particle and at (or near) the interphase between the aqueous acid and the polymer particle. We were led by kinetic experiments to conclude that the two loci do react at different rates and by different mec...

803. Kinetics and mechanism of hydrochlorination of synthetic and natural polyisoprene latex

Abstract The kinetics of hydrochlorination of synthetic polyisoprene emulsions, prepared by new and simple methods, are studied for comparison with the same reaction of natural latex. Nearly identical zero-order rate constants apply to both substrates at 300° K and 1 or 2 atmospheres of hydrogen chloride, despite differences in the detailed structure of the polymers. The conclusion that the substrates are not concerned in the rate control follows, since the rates of chain reactions which might give zero-order constants are very sensitive to the detailed structure of the polymers. Two initial rate abnormalities are observed. The first is shown to be due to a fast surface reaction, the second probably reflects the presence of a basic retarder in natural rubber particles only. Similar abnormalities of the cyclization reaction, reported earlier, are explained similarly. The effects of energetic factors and concentration on the hydrochlorination rate support visualization of the simple rate-determining step as...