Intramolecular branching in polyvinyl acetate

Abstract

Abstract The polymerisation of vinyl acetate at various temperatures between+18°C. and −50°C. to various conversions has been carried out to obtain polymers with different degrees of branching. All polymer samples showed a fall in intrinsic viscosity after hydrolysis and reacetylation. This change is related to the amount of branching in the original polymer, but the relationship did not become clear for unfractionated material. One sample was fractionated, and the fractions studied by following the changes in intrinsic viscosity and osmotic molecular weight occurring on hydrolysis and reacetylation. The fractionated sample was made from radio‐active initiator, which enabled the number of catalyst‐fragments per molecule to be counted. An intramolecular branching mechanism is proposed to explain the incidence of branch points in molecules which are in effect linear.