Multiphase separation model for binary mixed micelles

Aggregation of Mixed (Cationic + Anionic) and (Cationic + Nonionic) Surfactant Systems within a (Lanthanide Salt:Urea) Deep Eutectic Solvent

Deep eutectic solvents (DESs) are emerging as versatile media to support and facilitate various molecular aggregation processes, including surfactant self-assembly. The effect of a type IV DES consisting of La(NO3)3·6H2O and urea in a 1:3.5 molar ratio named (La:U) as a solubilizing medium on the self-aggregation of (cationic + anionic) and (cationic + nonionic) surfactant mixtures with N-dodecyltrimethylammonium bromide (DTAB), sodium dodecyl sulfate (SDS), and Triton X-100 (TX-100) as cationic, anionic, and nonionic surfactants, respectively, is investigated. The surfactant mixtures are found to readily self-aggregate within the (La:U) DES across the complete composition range under ambient conditions. The critical aggregation concentrations (CACs) of both (DTAB + SDS) and (DTAB + TX-100) surfactant mixtures lie between the CACs of the respective surfactants in the mixture, indicating that, owing to its ionic nature, the (La:U) DES effectively screens the charges present on the surfactant headgroups. While for the (DTAB + SDS) mixture, this observation is in contrast to that in aqueous media, it is similar to that in water for the (DTAB + TX-100) mixture. Both investigated surfactant mixtures exhibit a mostly negative interaction parameter (β) within the DES, implying the presence of predominantly attractive interactions between DTAB and SDS/TX-100. The thermodynamic parameters estimated for both surfactant mixtures within the (La:U) DES indicate aggregation to be a spontaneous process. While it appears to be both enthalpically and entropically driven, it is predominantly entropically driven. Using fluorescence spectroscopic methods, the aggregation number (Nagg) of the self-assembly of mixed surfactant systems is estimated and the solute solvation microenvironment afforded by these aggregates within the (La:U) DES is also ascertained. The outcomes will help expand the application potential of such polar DESs by establishing them as alternate and effective media for mixed surfactant aggregation.

Scrutinizing Self-Assembly, Surface Activity and Aggregation Behavior of Mixtures of Imidazolium Based Ionic Liquids and Surfactants: A Comprehensive Review

The desire of improving various processes like enhanced oil recovery (EOR), water treatment technologies, biomass extraction, organic synthesis, carbon capture etc. in which conventional surfactants have been traditionally utilized; prompted various researchers to explore the self-assembly and aggregation behavior of different kinds of surface-active molecules. Ionic liquids (ILs) with long alkyl chain present in their structure constitute the advantageous properties of surfactant and ILs, hence termed as surface-active ionic liquids (SAILs). The addition of ILs and SAILs significantly influence the surface-activity and aggregation behavior of industrially useful conventional surfactants. After a brief review of ILs, SAILs and surfactants, the prime focus is made on analyzing the self-assembly of SAILs and the mixed micellization behavior of conventional surfactants with different ILs.