How ionic liquid composition affect Raffinate 1 polymerization in a cationic system?

This research investigates the polymerization of Raffinate 1 under mild conditions using AlCl₃-based initiating systems incorporating five different ionic liquids: [MIM]⁺[HSO₄]⁻, [Py]⁺[HSO₄]⁻, [CycIM]⁺Cl⁻, [PVIMCyc]⁺Cl⁻, and [PVIM]⁺[HSO₄]⁻. The resulting polybutenes were characterized to determine exo-olefin content, number-average molecular weight (Mₙ), and molecular weight dispersity (Ð). The exo-olefin content of the polymers was below 12 %, with Mₙ values ranging from 6000 to 9500 g/mol and Ð values below 2.03. Compared to the neat AlCl₃/ethanol system, the incorporation of ionic liquids generally led to polybutenes with lower Mₙ, comparable or slightly higher Ð, and similar exo-olefin content. Deconvolution of the GPC curves revealed that all polymers featured three distinct active sites. Among these, the site producing low-molecular-weight polymer chains exhibited the lowest activity, contributing less than 10 wt% to the total polymer population. Additionally, Density functional theory calculations via Natural Bond Orbital analysis showed that the average NBO charge on aluminum in the (AlCl₃)₂ dimer complexes was more positive for ILs than for PILs and S-ILs. These NBO charges revealed a nonuniform distribution between the two aluminum centers upon bonding with the hydroxyl group, with an increase in positive charge on the aluminum center coordinating the hydroxyl.