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Mundil, Robert; Hermanova, Sona; Peschel, Martin; Lederer, Albena; Merna, Jan (2018): On the topology of highly branched polyethylenes prepared by amine-imine nickel and palladium complexes: the effect of ortho-aryl substituents. In: Polymer International, Vol. 67, No. 7: pp. 946-956
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Series of nickel and palladium complexes bearing amine-imine ligands in various ortho-aryl and backbone positions were prepared and investigated in ethene polymerization. Ethene polymerization initiated by symmetrically ortho-substituted nickel and palladium amine-imine catalysts is controlled. Mono-substitution in the ortho-aryl positions of nickel complexes is not as efficient in protecting centers from chain transfer as di-substitution. Both the central metal and the size of the ortho-aryl substituent have a significant effect on the polyethylene (PE) topology. Based on detailed characterization by high temperature SEC-IR-, SEC with multi-angle laser light scattering and C-13 NMR data, PEs prepared by nickel amine-imine complexes have a linear rather than dendritic topology. In contrast, palladium amine-imine complexes with small ortho-aryl substituents at low ethene pressure were shown for the first time to form dendritic PEs with topology comparable to PEs formed by -diimine palladium catalyst.