Ethylene/Propylene Copolymerization and Ethylene/Propylene/5-Ethylidene-2-Norbornene Terpolymerization Using Half-Sandwich Titanium Complexes with α-Naphthoxide Ligands as Catalysts

A novel half-sandwich titanium complex, Cp*Ti(1-C10H7O)Cl2, containing an α-naphthoxide fragment, was synthesized. Modified methylaluminoxane (MMAO-12) and perfluoroaryl boron-containing activators B(C6F5)3 and [Ph3C][B(C6F5)4] combined with triisobutylaluminum were used to activate the precatalyst. The resulting catalysts produced binary and ternary copolymers of ethylene with propylene and 5-ethylidene-2-norbornene. The composition, molecular weight characteristics, and thermophysical properties of the copolymers—including those of ethylene/propylene copolymer samples after stepwise isothermal melt crystallization—were characterized. The copolymerization performance of the catalysts was compared with previously studied similar systems based on the half-sandwich titanium complex Cp*Ti(O2,6iPr2C6H3)Cl2. The properties of the copolymers were also assessed comparatively. The synthesized catalytic systems produced polymer mixtures consisting of low-molecular-weight (comonomer-enriched) fractions and high-molecular-weight polyethylene fractions, likely due to the generation of two different types of active sites responsible for producing bimodal copolymers.