(83c) Dynamically Cross-Linked Polyolefin Elastomers with Highly Improved Mechanical and Thermal Performance

Polyolefin elastomer (POE) has important applications in automotive industry, medical equipment, and electrical engineering. However, further improvement of their mechanical performance and heat resistance without reducing their processing properties is urgently desired while remains a great challenge. Herein, we propose the use of dynamic cross-linking method to address this issue. We first prepared copolymers of ethylene, 1-octylene, and 5-vinyl-2-norbornene with Mws of 120~170 kDa and modified them via thiol-ene click chemistry to introduce hydroxyl groups at contents of 0.8~2.1mol.%. They were further cross-linked with bis-dioxaborolane via melt extrusion. The cross-linked POEs (CPOs) present significantly improved tensile strength and Young's modulus by 137% and 74.1%, respectively, while little change of the elongation at break. They also maintain a steady storage modulus plateau of 2.9 MPa above 100℃, in contrast to a drop to 0.2 MPa for pristine POEs. Moreover, these CPOs with dynamic boronic ester linkers could be reprocessed with a recovery ratio of tensile strength at break to 81.1% after reprocessing three times. Our strategy thus permits the development of higher-performance POE materials without degradation of their recyclability.