Hyperbranched Polyethylene Ionomers Containing Cationic Tetralkylammonium Ions Synthesized by Pd–Diimine-Catalyzed Direct Ethylene Copolymerization with Ionic Liquid Comonomers

Abstract

Synthesis of polyolefin-based ionomers through direct catalytic copolymerization of olefin with ionic comonomers has been challenging with no prior reports. We demonstrate in this article the first direct synthesis of a class of hyperbranched polyethylene ionomers containing positively charged tetralkylammonium ions and different counteranions (tetrafluoroborate, hexafluorophosphate, bis(trifluoromethane)sulfonimide, or hexafluoroantimonate) by copolymerization of ethylene with tetralkylammonium-containing acrylate-type ionic liquid comonomers (3–5, 7). The use of a Pd–diimine catalyst (1), which shows excellent stability toward the highly polar ionic group, is key to the direct synthesis. A detailed study on the catalytic copolymerization and the effects of the polymerization condition on the macromolecular chain parameters of the resulting ionomers has been performed. A range of ionomers differing in ion content and counteranion has been synthesized and characterized. Meanwhile, systematic studies on th...