High-Performance Elastomer from Trans-1,4 Copolymerization of Ethylene and Butadiene

Copolymerization of ethylene (E) and butadiene (BD) is rather difficult due to their unmatched reactivity and incompatible mechanism, and high-efficient preparation of amorphous and random E/BD copolymers with high molecular weight is more challenging. Herein, we report the copolymerization of E and BD using the half-sandwich fluorenyl scandium complex and the constrained geometry configuration scandium complexes attached to pyridinyl fluorenyl and N-heterocyclic carbene fluorenyl ligands. The scandium precursor bearing moderate sterics and medium Lewis acidity exhibited the highest activity thus far reported (1.64 x 10(6) g mol(sc)(-1) h(-1)), since either E or BD unit-ended active species facilitates cross-propagation to successfully avoid the poisonous effect of high BD loading for E incorporation. Therefore, high-molecular weight copolymers featuring trans-1,4 regularity and alternating sequence in major were isolated. Noted that, there are small percentages of cis-1,4/1,2-units and cyclohexane ring along the E/BD copolymer backbones. This structural defect dramatically reduces the melting temperature and enthalpy of the copolymers and damages the crystallinity, strikingly, which endows E/BD copolymer vulcanizates excellent mechanical and physical properties on tensile strength, puncture resistance, aging resistance, and rolling resistance as well as abrasion resistance, surpassing the commonly employed natural rubber and styrene-butadiene rubber.