DEGRADATION OF EPOXIDIZED POLYENES IN THE PRESENCE OF PHTHALIC-ACID

Viscometry was used to follow the epoxidation of polybutadiene and styrene-butadiene triblock copolymers (SBS) with monoperoxyphthalic acid (MPPA). Long reaction periods lead to an abnormal increase and then a drop in reduced viscosity. The increasing viscosity is due to repulsion between the oxitrane group and its ring-opening product with phthalic acid, while the viscosity drop can be correlated with a decrease in molecular weight. Long-term storage of the epoxidized polyenes in the reaction solution containing phthalic acid, which is the derived product from MPPA, also leads to a dramatic decrease in molecular weight. The occurrence of degradation was confirmed by gel permeation chromatographic (GPC) analysis of molecular weight and molecular weight distribution. Chloroform accelerated the degradation reaction, possibly through the generation of hydrochloric acid. The degraded products were isolated and analyzed by GPC and NMR. A free radical mechanism was proposed for the oxidative degradation of epoxidized polyenes after excessive reaction.