Tandem Action of SNS–Cr and CGC–Ti in Preparation of Ethylene–1‐Hexene Copolymers from Ethylene Feedstock

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–CrCl 3 (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 10 5 –10 6 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 13 C 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. image