Salt Effect on the Aggregation and Thermodynamic Properties of Ionic Liquid ۱-Dodecyl-۳-methylimidazolium Bromide in Aqueous Solutions

Ionic liquids (ILs) have received considerable attention as greener replacements for traditional volatile organic solvents in a variety of 􀂿elds such as chemical synthesis, catalytic chemistry, electrochemical device, separation, and biomass dissolution because of their unique physicochemical properties [۱]. Recently, it has been reported that self-aggregation of imidazolium ILs occurs in solutions because of their inherent amphiphilic nature. Material preparation in ILs, chromatographic application of ILs, and environmental pollution control by ILs are often closely dependent on such aggregation behavior. Thus, the study of aggregation behavior of ILs in solutions is highly desired for the understanding of how IL participates in practical applications as a component [۲]. In recent years, a number of research publications indicated aggregates formation of ILs in aqueous solutions. It was found that the aggregation behavior of ILs can be regulated and controlled by designing the alkyl chain length, cationic structure, and anionic type of the ILs. Literature survey reveals that aggregation behavior of ILs can also be tuned by the addition of some inorganic salts, but the related investigation is verylimited [۳]. Therefore, a systematical study on the effect of the salt nature on the aggregation behavior of ILs is necessary from the viewpoint of fundamental and applied aspects. This work aims to study the regulated and controlled effect inorganic cations of the added salts on the aggregation behavior of ۱-dodecyl-۳-methylimidazolium bromide ([C۱۲mim]Br) in aqueous solutions. For these purposes, ۵ chloride salts (NaCl, KCl, NH۴Cl, (CH۳)۴NCl, MgCl۲) were selected, and conductivity at ۲۹۸.۱۵ to ۳۱۳.۱۵ K, osmotic coefficient at ۳۰۸.۱۵ K, volumetric at ۲۸۸.۱۵ to ۳۱۳.۱۵ K are combined to study the salt effect on the aggregation of [C۱۲mim]Br. The results have been discussed from the in􀃀uence of the nature and size of salt on the critical micelle concentration (CMC), the degree of cationic binding at the aggregates surface (B), thermodynamic parameters of micellization (ΔGm°, ΔHm° , ΔSm° ), of the ionic liquid in aqueous solutions.

کلیدواژه ها:

Ionic liquid ، Aggregation ، Salt effect