Polymerization and characterization of ethylene/propylene and ethylene/1‐octene copolymers produced with bridged Zr‐ and Hf‐based metallocenes

Ethylene/propylene (E/P) and ethylene/1‐octene (E/O) copolymers were polymerized with two bridged metallocene catalyst systems, Et(Ind)2ZrCl2/MAO and Et(Ind)2HfCl2/MAO, respectively. The copolymers produced and some commercial reference copolymers were characterized by DSC, SEC, DMA and 13C NMR. The Hf‐catalysed E/P polymerizations showed much lower activities than the corresponding Zr‐catalysed polymerizations but gave polymers with high molar mass. The Hf‐based copolymers also showed two melting peaks which may be indicative of several active sites of the catalyst. A comparison of E/P copolymers, containing about 20 mol‐% propylene and produced with Zr, Hf and homogeneous V‐catalysts, respectively, indicated that the Hf and V‐catalysts gave material more similar to each other. The E/O copolymers produced with Zr‐catalysts gave very low molar masses and the reactivity ratios, calculated from the NMR data, indicated that the Hf‐catalyst has a slightly higher reactivity for 1‐octene and the Zr‐catalyst some better reactivity for ethylene. Segregation fractionation studies by DSC indicated that a lower 1‐octene feed gives more heterogeneous copolymers and the DMA measurements reveal the existence of a linear correlation between the 1‐octene content and the intensity of the tan δmax peak.