Influence of Type and Content of Various Comonomers on Long-Chain Branching of Ethene/α-Olefin Copolymers

One polyethylene and nine ethene/α-olefin copolymers differing in amount (0.4−2.9 mol %) and molar mass of the comonomer were characterized by NMR, SEC-MALLS, and rheology. Samples were polymerized using a [Ph2C(2,7-di-t-BuFlu)(Cp)]ZrCl2/MAO catalyst, with octene, octadecene, and hexacosene as comonomers, resulting in polymers of M w ≈ 190 kg/mol. The comonomer content was determined by melt-state NMR. For the homopolymer 0.37 and 0.30 LCB/molecule were found by NMR and SEC-MALLS, respectively. Rheological quantities, such as the zero shear rate viscosity (η0), increased with LCB as compared to linear samples of the same M w. The shape of the viscosity function and the linear steady-state elastic compliance ( ) showed a dependence on comonomer content and length. These findings are used to elucidate the various long-chain branching architectures. The highest comonomer content samples behaved like typical linear polymers in rheological experiments, while those with less comonomer contents were found to be long-chain branched. Besides the comonomer content, the type of comonomer has an influence on the branching structure.