Synthesis and characterization of random or gradient butadiene-p-methylstyrene copolymers via anionic polymerization

Copolymers of 1,3-butadiene and p-methylstyrene (p-MS) were synthesized via anionic polymerization. A benzophenone-potassium complex was added to tune the reactivity ratio of the two monomers, leading to random and gradient composition along the copolymer chain. The overall composition and microstructure could be controlled and well characterized by GPC and ¹H-NMR. The p-MS was distributed from gradient to random with increasing the content of the benzophenone-potassium complex, and the 1,2-microstructure in the polybutadiene sequence increased at the same time. The hydrogenation of the copolymer of 1,3-butadiene and p-MS resulted in the corresponding saturated copolymer with welldefined structure and narrow molecular weight distribution.