Ionic liquids as modifier for the oligomerization of α-olefins to reactive poly (α-olefins) via traditional AlCl3 catalyst

Abstract

In the polymerization there are series of systems that are traditionally used because their procedures are well established, and it is not considered necessary to leave the comfort zone. Here, it is proposed to reevaluate the cationic initiator system with a trident of IL/AlCl3/H2O (IL: ionic liquid). Thus, different ILs comprising of similar anionic part, however various cationic moieties; based on triethanolamine (TEA), tributylamine (TBA), and pyridine (Pyr) precursors; were synthesized and evaluated together with AlCl3 in the cationic polymerization of 1-decene. According to the GPC results, while Pyr and TBA-based ILs suppressed molar mass of poly(α-olefins) (PAO), compared to PAO from neat AlCl3, TEA containing IL enhanced it. This affirms outstandingly higher performance of the IL/AlCl3 than AlCl3/H2O. According to the 13C NMR data, PAOs from IL containing initiators have higher content of long chain branching, which is beneficial to improved viscosity index characteristic. Kinematic viscosity results were in accordance with the molar mass and 13C NMR data. 1H NMR spectra point to the fact that PAOs derived from TEA and TBA-based ILs generate exo-olefins, a type of vinyl that leads to reactive oligomers with potential capacity for block copolymers. DFT theoretical calculations and studies of non-covalent interactions help to separate and understand how the nature of the IL translates into such different properties.