Ethylene/Propylene Copolymerization and Their Terpolymerization with 5-Ethylidene-2-norbornene over Catalytic Systems Based on Half-Sandwich Titanium Complexes with Organoaluminum and Organoboron Activators

Abstract

Half-sandwich titanium complexes, specifically Cp*TiCl₃ and Cp*Ti[O(2,6-ⁱPr₂-Ph)]Cl₂, were investigated as catalytic precursors for the synthesis of ethylene/propylene copolymers and ethylene/propylene/5-ethylidene-2-norbornene terpolymers. For this purpose, a variety of activators were tested: modified polymethylaluminoxane; boron-containing compounds such as B(C₆F₅)₃ and Ph₃CB(C₆F₅)₄ in combination with triisobutylaluminum (TIBA); isobutylaluminoxane (IBAO), and isobutylaluminum aryloxide (2,6-^tBu₂,4-Me-PhO-)AlⁱBu₂ (Al_BHT). In the copolymerization of ethylene and propylene, the catalysts exhibited high activity when activated by MMAO-12 and TIBA+Ph₃CB(C₆F₅)₄ but low activity with TIBA+B(C₆F₅)₃ and Al_BHT. With IBAO as an activator, these catalysts were found to be totally ineffective. The catalysts exhibited low activity in terpolymerization. It was further revealed that more than one type of active sites was generated in the catalytic systems: these sites were responsible for simultaneous formation of low-molecular-weight and ultrahigh-molecular-weight polymers. The composition of the copolymers as well as their thermophysical and physicomechanical properties were shown to depend on the type and composition of the catalytic system.