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.