Coordination Terpolymerization of Ethylene, Butadiene, and Styrene Using Thioanisole-Modified Rare-Earth Catalysts

The terpolymerization of ethylene (E), butadiene (BD), and styrene (St) is highly challenging due to their divergent reactivities and less compatible polymerization mechanisms. Herein, we report the successful coordination polymerization of E/BD/St by using newly designed thioanisole-modified constrained geometry configuration (CGC) rare-earth metal complexes. The isolated E-BD-St terpolymer possesses a unique structure composed of syndiotactic polystyrene (sPS) blocks, high cis-1,4 (ranging from 78.4 to 81.4%) polybutadiene (cis-1,4 PBD) blocks, and very short polyethylene (PE) or discrete E units incorporated into the above two types of blocks. The multiblock structure of the E-BD-St terpolymer enables microphase separation along with high compatibility with other rubbers. Consequently, the vulcanizate of SBR(styrene–butadiene rubber)/E-BD-St blend exhibits significantly higher tensile stress and superior elongation at break than those of the SBR/BR composite and SBR alone. The rolling resistance of the SBR/E-BD-St vulcanizate was also significantly improved. It is noted that E/BD/St terpolymerization was achieved by the yttrium complex─a metal center usually inert toward E polymerization, and the selectivity resulted from the concerted effects of the steric bulkiness or geometry of the ligand and the coordinating monomer. This work paves a new avenue for fabricating high-performance polymer materials from common monomers by the design of new catalysts that are unachievable via conventional methods.