Abstract
Ethylene–1-hexene copolymer materials, ranging from semicrystalline linear low-density polyethylene (LLDPE) to completely amorphous polyethylenes (PEs), are prepared from ethylene alone in a single reactor by the tandem polymerization of bis(2-dodecylsulfanyl-ethyl)amine–CrCl3 (SNS–Cr) and (N-tert-butylamido) (tetramethylcyclopentadienyl)–titanium dichloride (CGC–Ti) at 75 °C and under atmospheric pressure. The polymerization activities are on the order of 105–106 g (mol Ti)−1 h−1. 1-Hexene incorporation in the resulting copolymers can be adjusted by varying the Cr–Ti molar ratio and/or applying a short period of pre-trimerization. Copolymers with high 1-hexene incorporation up to 15 mol% are obtained. Few vinyl and vinylene chain ends are detected by 13C NMR, suggesting that 1-hexene does not act as a chain-transfer agent. Narrow molecular-weight distributions with polydispersities from 1.9 to 2.6 are obtained, characteristic of a single-active-site nature of the catalyst system.
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