Synthesis of Ultra-High molecular weight polyethylene elastomers by para-tert-Butyl dibenzhydryl functionalized α-Diimine nickel catalysts at elevated temperature

Abstract

The synthesis of polyethylene thermoplastic elastomers directly from ethylene as a feedstock is highly attractive in perception of their diverse applications and low cost. In this contribution, α-diimine nickel catalysts (Ni1-Ni4) with sterically bulky para-t-Bu dibenzhydryl moieties at ortho-position as well as different electron-donating and -withdrawing groups at para-position have been synthesized, characterized and applied for ethylene polymerization. These catalysts were found to be highly active with maximum activity up to 7.04 × 106 g·mol−1·h−1, producing polyethylene with ultra-high molecular weight of up to 333.4 × 104 g·mol−1. More remarkably, these catalysts have thermal stability of up to 140 °C. The t-Bu rich nature enables their good solubility in non-polar aliphatic hydrocarbons, which are industrially desired polymerization solvents. Furthermore, these catalysts generate polyethylene thermoplastic elastomers especially at industrially high temperature of 140 °C, with great mechanical properties and strain recover (SR) values of up to 75 %. The properties including high thermal stability, polymerization in aliphatic hydrocarbons, and capabilities of yielding elastic ultra-high molecular weight polymers make them highly attractive for potential industrial applications.