Synthesis of Aldehyde-Terminated Epoxidized Liquid Polybutadiene Rubber

Polybutadiene rubber is a synthetic elastomer with large scale applications in industry. Functionalization of polybutadiene and other polyolefins is a method to adjust their physical, chemical and mechanical properties [1]. However, preparation of functionalized polyolefins with controlled functionalities usually needs complex synthetic routs and accurate control of the reaction condition [2]. Herein, we prepared epoxide- and aldehyde-functionalized polybutadiene rubber by modification of pristine polybutadiene rubber. Polybutadiene rubber was dissolved in THF and treated with periodic acid. Periodic acid is an oxidizing agent which first reacts with vinyl groups (double bonds)to produce epoxide rings. The resulting epoxide groups can further react with periodic acid, and aldehyde groups are formed through epoxide ring opening and subsequent chain cleavage reactions. Therefore, an aldehyde-terminated epoxidized polybutadiene rubber is obtained at the end of the reaction (Fig. 1). The structure of the product was characterized by NMR spectroscopy and the presence of epoxide and aldehyde groups were confirmed. The epoxidation percent and molecular weight of the final product were also calculated. Because of the cleavage of the polymer chain, the molecular weight of the polymer is decreased and, thus, a viscous liquid functionalized polybutadiene rubber is obtained. Aldehyde-terminated epoxidized polybutadiene rubber with controlled molecular weights and epoxidation percents could be obtained by varying the amount of oxidant and the experimental conditions. This method is also promising for functionalizing other vinyl-containing rubbers.