Imidazolium-Based Zwitterionic Surfactants: Characterization of Normal and Reverse Micelles and Stabilization of Nanoparticles

Abstract

This paper presents the physicochemical properties of micellar aggregates formed from a series of zwitterionic surfactants of the type 3-(1-alkyl-3-imidazolio)propane-sulfonate (ImS3-n), with n = 10, 12, 14, and 16. The ImS3-n dipolar ionic surfactants represent a versatile class of dipolar ionic compounds, which form normal and reverse micelles. Furthermore, they are able to stabilize nanoparticles in water and in organic media. Aqueous solubility is too low at room temperature to allow characterization of micellar aggregates but increases with addition of salts, allowing determination of aggregation number and cmc. As expected, these parameters depend on the length of the alkyl chain, and cmc values follow Klevens equation. In the presence of NaClO4, all ImS3-n micelles become anionoid by incorporating ClO4(-) on the micellar interface. A special feature of these surfactants is the ability to form reverse micelles and solubilize copious amounts of saline solutions in chloroform. (1)H NMR and infrared spectroscopic evidence showed that the maximum water to surfactant molar ratio w0 achievable depends on the concentration and type of salt dissolved. Reverse micelles of the ImS3-n surfactants can be used to stabilize metallic nanoparticles, whose size may be tuned by the amount of water dissolved.

Chemical Tuning of Zwitterionic Ionic Liquids for Variable Thermophysical Behaviours, Nanostructured Aggregates and Dual‐Stimuli Responsiveness

“…It is proposed that the combined electrostatic interactions between the oppositely charged neighbouring zwitterionic groups of the ZILs along with hydrophobic interactions between the alkyl/vinyl/aryl substituents is responsible for the generation of ZIL aggregates in turbid suspensions. ILs usually do not aggregate, but some IL surfactants do aggregate into micelles in aqueous solution . These ZILs underwent self‐association into hierarchical aggregates of different morphologies from spheres to tripods, tetrapods, fern‐like, flower‐like, dendrite etc.…”

“…Recently, Stoffelen and Huskens reported azo‐carboxybetaine‐based self‐assembled zwitterionic supramolecular nanoparticles with pH and photo responsiveness in water . Another far less investigated ZI molecule, known as zwitterionic surfactant, was shown to be aggregated to reverse micelles in different solvents . Xie et al.…”

The mixing behaviour of anionic and nonionic surfactant blends in aqueous environment correlates in fatty acid ester medium

“…Sodium bis(2-ethylhexyl) sulfosuccinate (AOT, 99%) and polyoxyethylene (20) sorbitan trioleate (Tween-85) are purchased from Sigma, USA. AOT is dried at 60 • C for 48 h in a vacuum, stored over P 2 O 5 in a desiccator, and used without further purification.…”

“…[15,16]. In spite of extensive studies of micelles and RMs using similar set of surfactant(s) [17][18][19][20], a proper understanding at a molecular level is still in demand. In the presence study, we have investigated the effect of mixing of two surfactants (anionic and nonionic) on the physicochemical characterization of the mixed micellar solutions as well as the corresponding RMs in order to optimize and design their properties.…”

“…We explore the micellization behavior of an anionic, sodium di-2-ethylhexylsulfosuccinate (AOT) and nonionic, polyoxyethylene (20) sorbitan trioleate (Tween-85) surfactant and their mixtures in water. Micelle formation has been investigated using extensive surface tension measurements and analysis of experimental data.…”