High-Performance Elastomer from Trans-1,4 Copolymerization of Ethylene and Butadiene
Kai Zhang, Yanli Dou, Yang Jiang, Zhen Zhang, Shihui Li, Dongmei Cui
Abstract
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 × 106 g molSc–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.