Autoacceleration and Cyclization Effects on Styrene/Divinylbenzene Copolymerization

摘要

Copolymerizations of styrene with divinylbenzene (DVB) are carried out at low monomer concentrations in order to evaluate the incidence of cyclization reactions. The pendant double bond concentration in the synthesized polymers is measured using Fourier transform infrared spectroscopy. Reactions are carried out at monomer concentrations of 6% and 2% (v/v), DVB concentration in the range 15-80 wt% and temperatures in the range 60-90 degrees C. A previously developed model is used to interpret the results and analyze the cyclization effects. The predictions of the model accounting for cyclization reactions present a better agreement to the experimental data in comparison to predictions without cyclizations. Autoacceleration effects are observed for cases with higher DVB concentrations, in which the formation of highly entangled structures may have occurred. The model provides an estimate of 0.05 for the crosslink parameter (C-P) and 130 s(-1) for the rate constant of cyclization for the smallest sequence (three units) at 90 degrees C.