Chain Transfer to Monomer and Polymer in the Radical Polymerization of Vinyl Neo-decanoate

Abstract

Molecular weight distributions of poly(vinyl neo-decanoate) produced by the bulk polymerization of the monomer to low conversions were investigated to obtain values of the rate constants for the chain transfer to monomer ('Cm'). The value of 'Cm' of 7.5(±0.6)x10⁻⁴ was obtained from a logarithmic plot of the number distribution at 5, 25, and 50°C, which suggests that the activation energy for chain transfer is in the order of 20-25 kJ.mol⁻¹. These plots were linear between the number and weight-average degrees of polymerization, but not over the whole molecular weight range for which a significant signal was observed in the gel permeation chromatography (GPC) trace. Modeling suggests that the deviations observed at high molecular weights can be explained by branching of the chains through chain transfer to the polymer, with a branching density as low as 10⁻⁵ , without affecting the slope at low values of the number of monomer unit, N. This deviation from the expected distribution of linear chains was used to estimate the branching densities at low conversion.