An efficient initiator system containing AlCl3 and supported ionic-liquid for the synthesis of conventional grade polyisobutylene in mild conditions

Abstract

Ionic liquid based systems are used to facilitate the cationic polymerization of isobutylene to conventional grade polyisobutylene (PIB) using AlCl3 as an initiator. Specifically, the compound 1-butyl-3-methylimidazolium chloride (IL) is employed as a reference system due to its simplicity, as well as the polyionic liquid (PIL), prepared via radical polymerization of 1-butyl-3-vinylimidazolium chloride, and the halloysite clay (Hal) supported ionic liquid (S-IL). The overall results stated that the designed AlCl3/S-IL initiator system can be used as a safer and greener alternative to the industrially used BF3 system, in the development of isobutylene polymerizations under mild reaction conditions to conventional grade PIB for viscosity improvement applications. The microstructure and final properties of the as-synthesized PIB was unraveled and compared to Indopole 2100, as a commercial PIB. DFT calculations were performed to understand the different performance of IL and PIL with respect to the S-IL system, and also to show why the catalyst loading for the latter system is lower, as well as to understand how each of the three systems sequesters the catalyst AlCl3. Since the interaction is non-covalent or ionic, in addition to NBO charges, NCI plots were also used.