Iodine‐Transfer Polymerization (ITP) of Ethylene and Copolymerization with Vinyl Acetate
Résumé
The first example of a controlled radical polymerization of ethylene using iodine transfer polymerization (ITP) is performed under mild conditions (≤ 100 °C and ≤ 200 bar). Different commercially available, cheap, and non-toxic iodo alkyls (R-I) were used as chain-transfer agents (CTAs) in combination with 2,2'-azobis(2-methylpropionitrile) (AIBN) to investigate the impact of the R-group on the polymerization behaviour. These systems showed no rate retardation and no significant loss of chain ends. The formed well-defined end-capped polyethylene-iodine (PE-I) species is very stable upon storage. Narrow molar-mass distributions with dispersities around 1.6 were obtained up to number average molar masses Mn of 7300 g mol-1. The copolymerization by ITP (ITcoP) of ethylene with vinyl acetate (VAc) to form poly(ethylene-co-vinyl acetate) (EVA) copolymer was also successful. By fine tuning the ethylene pressure and the vinyl acetate content, a broad range of copolymers containing from 0 to 85 mol% of VAc unit was achieved. By reactivating the iodo chain-end, block copolymer structures composed of ethylene and VAc such as poly(ethylene-co-vinyl acetate)-b-polyethylene (EVA-b-PE) or gradient block copopolymers EVA-b-EVA with different content of VAc in the blocks were obtained for the first time using ITP. This highly versatile synthetic platform provides a straightforward access to a diverse range of well-defined PE based polymer materials. Finally, reactivity trends were explored by a theoretical mechanistic study.
Domaines
Chimie
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