Preparation of polyethylene elastomers via controlled chain-walking ethylene polymerization for enhanced impact modification of polypropylene

Abstract

To develop a new polyolefin thermoplastic elastomer, it is crucial to focus on enhancing the impact modification of polypropylene. In this contribution, the successful synthesis of polyethylene thermoplastic elastomers with great mechanical and elastic properties via chain-walking ethylene polymerization using bulky α-diimine nickel catalysts bearing both the t-butylated dibenzhydryl and the p-substituted phenyl moieties. These bulky groups providing greater solubility and steric hindrance also led to great thermal stability and high activities of up to 1.1 × 10⁷ g·PE·mol·Ni^–1·h^–1, generating high molecular weight polyethylene with moderately branched microstructures (64–87 branches/1000 C). The branched polyethylene exhibited thermoplastic elastomer characteristics and demonstrated excellent elastic recovery properties up to 78%–85% by Ni2 and Ni3 respectively which is higher compared to Ni1 (SR % = 67%). Most importantly, the impact properties of polypropylene can be enhanced through the incorporation of a polyethylene elastomer blend, resulting in superior performance.