Influence of type and content of various comonomers on long-chain branching of ethene/α-olefin copolymers

One polyethylene and nine ethene/alpha-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 [Ph(2)C(2,7-di-t-BuFlu)(Cp)]ZrCl(2)/MAO catalyst, with octene, octadecene, and hexacosene as comonomers, resulting in polymers of M(w) approximate to 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 (eta(0)), 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 (J(e)(0)) 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.