Catalytic Epoxidation of Polybutadiene Rubber Using H2O2/CH3COOH and Na2WO4

Post-polymerization functionalization of polybutadiene and other rubbers is very interesting since it can be served to modify the properties of these rubbers. The double bonds present in the main chain of polybutadiene can be used for its functionalization and modification [1]. As one of the most well-known chemical reactions which can be performed on double bonds, epoxidation can be used to modify the properties of polybutadiene rubber. However, the yield of epoxidation of rubbers is very low for many common oxidation reagents and methods, and undesired side reactions can also occur [2]. Therefore, it is promising to develop new methods and reagents for efficient epoxidation of polybutadiene and other rubbers. We used sodium tungestate as catalyst to improve the efficiency of epoxidation of polybutadiene rubber and increase the yield of the reaction. Polybutadiene rubber was dissolved in THF and epoxidized by H2O2/acetic acid as oxidant in the presence of sodium tungestate as catalyst (Fig. 1). After extraction and purification, the modified rubber was characterized instrumentally. NMR spectra confirmed epoxidation of polybutadiene rubber and no significant byproduct was detected. The results indicate that epoxidation is the main reaction performed in the mixture and no undesired side reactions occurs during the process. The epoxidation percent of the product was also calculated. It was found that the epoxide content of the product can be adjusted by controlling the experimental condition such as reactant ratios and other experimental conditions. Epoxidation was increased by increasing the amount of oxidant/catalyst system. The reaction proceeded with high yield in mild condition and epoxidized polybutadienes with high epoxidation percents up to 35% was obtained.