Salt Effect on the Aggregation Behavior of 1-Decyl-3-methylimidazolium Bromide in Aqueous Solutions

Abstract

Understanding of the specific salt effect on the aggregation behavior of ionic liquids (ILs) is relevant to multiple applications. In this work, the influence of a series of 15 salts on the aggregation behavior of [C(10)mim]Br in aqueous solutions has been investigated by conductivity, fluorescence, and dynamic light scattering. It was shown that NaCl, NaBr, NaI, CH(3)CO(2)Na, NaSCN, NaNO(3), NaBrO(3), NaClO(3), C(6)H(5)COONa, Na(2)CO(3), Na(2)SO(4), Na(2)C(4)H(4)O(6), and Na(3)CH(5)O(7) have salting-out effect, whereas FeBr(3) and AlBr(3) have salting-in effect on the aggregation of [C(10)mim]Br in aqueous solutions. The effect of anions of the added sodium salts on the critical aggregation concentration (CAC), degree of anionic binding (beta), and aggregation number (N(agg)) of the IL basically follows the Hofmeister series, and the CAC values decrease but the beta and N(agg) values increase with increasing concentration of the salts. Hydrophobicity of the anions is suggested to play important roles in the salt effect on the aggregation of [C(10)mim]Br in aqueous solutions. Furthermore, the IL aggregates were found to grow slowly as the increase of the salt concentrations under studied static conditions, and resulting in the increased aggregation number of the IL. These results are expected to be useful in the applications of ionic liquids.

Surface adsorption and micelle formation of imidazolium-based zwitterionic surface active ionic liquids in aqueous solution

“…However, temperature, pH, and low salt concentration have a slight effect. This behavior is similar to that of some zwitterionic surfactants, such as C 12 H 25-N(CH 3 ) 2 CH 2 COO À [43] and dioctanoylphosphatidylcholine (diC 8 PC) [64], but is different from that of cationic SAILs, such as [C n mim]Br [20,41]. This demonstrates the surface adsorption and micelle behavior of the zwitterionic SAILs are analogous to traditional zwitterionic surfactants rather than cationic SAILs.…”

“…Numerous SAILs based on imidazolium, pyridinium, pyrrolidinium cations with different hydrocarbon chain lengths were studied extensively using a variety of methods, such as surface tension, 1 HNMR, steady-state fluorescence spectroscopy, and conductivity measurements [10][11][12][13][14]. Additionally, the effects of anionic nature (e.g., Cl À , Br À , NO À 3 , I À , BF À 4 , CF 3 SO À 3 , CH 3 COO À , ClO À 4 ) [15][16][17][18], various organic additives [19], and salts [20] on the aggregation behavior of SAILs in aqueous solutions were investigated. All the above studies indicate that we can control the aggregation behavior of SAILs in aqueous solutions by altering the alkyl chain length, cationic ring structure, and anionic type, as well as organic additives and salts.…”

Aggregational Attitude of Hexadecyltrimethylammonium Bromide in Aqueous Solutions of Sodium Salt at 298.15k

“…Reports has shown that [2,31] counter-ions with large size bind more effectively to micelle surface which promote decrease in electrostatic repulsion between the head groups of surfactant, thereby increase surfactant aggregational tendency resulting into depression of its CMC value. Addition of salt to aqueous media of HTABr lead to the partial reduction of the water of hydrophobic hydration around the alkyl chain of the non-associated surfactant monomers which decreased the energy required to break down this structure during micellization process [18].…”

Effect of mixed micellization on dimensions of 1-butyl-3-methylimidazolium dodecylsulfate micelles in presence of electrolytes

“…The modification of interfacial activity and aggregate size/ morphology are crucial for their optimum performance. Such modifications can be achieved by modifying surfactants' own structure [71][72][73] or mixing them with each other [63,64,[74][75][76][77] as well as with additives like salts and different organic compounds [21,[43][44][45][46][47][78][79][80][81]. Considering the need to control aggregate size, vital for various applications, we attempted to investigate the mixed micellization between [bmim] [DS] and Brij30 in presence of two different ions (Na + and NH 4 + ) using dynamic light scattering (DLS), small angle neutron scattering (SANS) and Rheological measurements.…”