Pressure-Sensitive Supported FI Catalyst for the Precise Synthesis of Uni- and Bimodal Polyethylene

Abstract

Pressure-sensitive phenoxy-imine titanium catalyst (FI-catalyst) was successfully synthesized by covalently immobilizing it on the surface of functionalized polystyrene (PS) nanoparticles, which acted as a support and a giant ligand simultaneously. The supported catalyst shows high catalytic activities in ethylene polymerization. Utilizing this catalyst, a serious of unimodal polyethylenes with tailored molecular weights ranging from 2 000 000 to 300 000 were produced under various reaction pressures and temperatures. Particularly, when the polymerization pressure was shifted during the reaction, the ethylene polymer with bimodal molecular weight distribution was successfully synthesized in only a single reactor. Differential scanning calorimetry analysis of the resultant polyethylene revealed a large difference between crystallinities at the first and second heating cycles, indicating that the synthesized polyethylene is of low entanglement.