Branching mechanisms in the polymerization of vinyl acetate

Abstract

AbstractA mechanism is proposed for branch formation in polyvinyl acetate. A simplified kinetic analysis gives the degree of branching in terms of six rate constant ratios. Four of these ratios were determined with satisfactory accuracy by very slow photopolymerization of highly purified vinyl acetate at 70°C. to different degrees of conversion. The polymers were believed to be near the maximum molecular weight obtainable at that temperature. Number‐average degrees of polymerization were estimated by quantitative determination of the double bond end groups. The correlation between these values and intrinsic viscosities was in good agreement with published osmotic and viscosity measurements. A fifth ratio was estimated less accurately by viscosity measurements on the polymers after alcoholysis and acetylation. A rough estimation of the sixth ratio was based on a cross‐linking experiment. These ratios were used to accurately predict the degradation on hydrolysis of a series of low molecular weight polymers. Calculations showed greater branching occurs in a single kettle continuous process than in the simple batch process.