Power-law distribution of molecular weights of nonlinear emulsion polymers

Abstract

AbstractIt is shown that power-law distributed polymers can be synthesized via nonlinear emulsion polymerization. Theoretical simulation results demonstrate that emulsion polymers formed with polymer transfer reactions during interval II approach a power-law distribution as polymerization proceeds. The exponent α of the weight fraction distribution, W(M) ~ M -α, satisfies the simple relationship α = 1/Pb, where Pb is the probability that the chain end is connected to a backbone chain. This relationship can be used to estimate the polymer transfer constant on the basis of the measured molecular weight distribution. The branched polymer structure is significantly different from randomly branched polymers. The expected branching density of the large-polymer limit is equal to that for Pb = 1 of randomly branched polymers, irrespective of the magnitude of Pb in the emulsion polymers. A preliminary investigation shows that power-law distributed polymers can also be synthesized via crosslinking emulsion polymerization.