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

Abstract

This research investigates the polymerization of Raffinate 1 under mild conditions using All₃-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−1 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

This research was funded by the Iran National Science Foundation under the grant number of 4023556, and by the Spanish Ministerio de Ciencia e Innovación with projects PID2021-127423NB-I00 and PID2024-155989NB-I00, and the Generalitat de Catalunya with project 2021SGR623. Financial supports from the project 3 A-Italy, MICS–PNRR MUR-M4C2-I 1.3 (PE00000004) are gratefully acknowledged

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