Formation of a novel bio-based elastomer from polybutadiene and epoxidized soybean oil via post-living anionic polymerization

The aim of this research was to develop a novel bio-based elastomer, chain-end functionalized polybutadiene (PBD), from epoxidized soybean oil (ESO), to be used as a processing aid for commercial PBD. This material was successfully synthesized in this study via post-living anionic polymerization of poly(butadienyl) lithium and ESO. The gel permeation chromatography revealed that the products had a mixture of molecular weights, comprising roughly three, two, and one times higher than that of the pure PBD. The majority of the molecules in the product had a two-fold higher molecular weight at the peak value (M-P) than the original PBD chain. The result obtained from the reaction of PBD anions with epoxidized methyl oleate indicated that the ester group showed the higher reactivity toward the PBD anion than the epoxide group. Therefore, the formation of bio-based elastomer from the PBD anions and ESO occurred via the nucleophilic substitution of PBD anion with the carbon atom of the ester group with the loss of the leaving group, the alkoxide, and then followed by nucleophilic addition of another PBD anion to the newly formed ketone, yielding an alcoholate anion. The alcoholate anion was then terminated by hydrogen abstraction from methanol, leading to the formation of chain-end epoxidized fatty acid ester functionalized PBD. The ring opening of the epoxide group of the ESO also took place simultaneously, yielding the product with the three-fold higher M-P than the original PBD. However, the ring opening of epoxide group was decreased when the size of the PBD anion and the amount of the ESO in the reaction were increased.