The Chameleon‐Like Nature of Zwitterionic Micelles: The Effect of Ionic Liquid Addition on the Properties of Aqueous Sulfobetaine Micelles

Abstract

We used fluorescence probing, ζ potentials, and dynamic light scattering measurements to study the interactions between the zwitterionic surfactant N-hexadecyl-N,N-dimethylammonio-1-propanesulfonate (SB-16) and three ionic liquids (ILs), 1-ethyl-3-methylimidazolium ethylsulfate ([C(2)mim][C(2)SO(4)]), 1-ethyl-3-methylimidazolium n-butylsulfate ([C(2)mim][C(4)SO(4)]), and 1-ethyl-3-methylimidazolium n-hexylsulfate ([C(2)mim][C(6)SO(4)]). The three ILs have the same cationic part and their anionic parts differ only in the length of the alkyl chain. The aim of our work is to offer a comparative study and establish the role of the alkyl chain length of the anion of ILs on 1) the incorporation of these anions in the zwitterionic micelles of SB-16 (selectivity of anions) and 2) the physicochemical properties of aqueous solutions of SB-16. Results show that, at lower concentrations (i.e. ≤20 mM), the different ILs modify the properties of the aqueous SB-16 solution in similar manner. All of them bring about a decrease in the critical micelle concentration (CMC) and also in size, and increase the aggregation number of the SB-16 micelles; these effects are more dramatic when [C(2)mim][C(6)SO(4)] is used as the additive rather than [C(2)mim][C(4)SO(4)] and [C(2)mim][C(2)SO(4)]. It is proposed that, in case of [C(2)mim][C(6)SO(4)], the presence of a hexyl chain on the hexylsulfate ion allows the ion to align itself with the tail part of SB-16, whereas, in the case of [C(2)mim][C(2)SO(4)], the presence of ethyl chain in the ethylsulfate ion is not sufficient to bring about a similar alignment of the ethylsulfate anion with the tail part of SB-16. This difference in the location of the anions of the ILs is responsible for the different behavior of the ILs.

Zwitterionic micelles as a soft template for the extremely rapid synthesis of small hollow gold nanocontainers

“…Moreover, with the addition of ILs, DAF and DAH the size of the SB-16 micellar aggregate decreases irrespective of the temperature, this is well supported by our earlier observations. 61 The f potential indicates the degree of repulsion between adjacent similarly charged aggregates in the solution. The absolute value of f potential is the potential difference between the dispersion medium and the stationary layer of fluid attached to the dispersed micellar aggregates.…”

“…The relatively higher negative value of f potential in case of DAH can be accounted for by the presence of long alkyl chain in hexanoate ion which helps in the incorporation of DAH in micellar system. 61 Using 28 mM aqueous solution of N-hexadecyl-N,N-dimethylammonio-1-propanesulfonate (SB-16) zwitterionic surfactant, we have prepared our desired soft template. Although, the critical micelle concentration of SB-16 was found to be 0.096 mM, 61 we have chosen higher concentration of SB-16, owing to the fact that the CMC changes drastically with the addition of ionic liquids.…”

“…61 Using 28 mM aqueous solution of N-hexadecyl-N,N-dimethylammonio-1-propanesulfonate (SB-16) zwitterionic surfactant, we have prepared our desired soft template. Although, the critical micelle concentration of SB-16 was found to be 0.096 mM, 61 we have chosen higher concentration of SB-16, owing to the fact that the CMC changes drastically with the addition of ionic liquids. 61 Two identical solutions were prepared by adding 20 mL of 20 mM HAuCl 4 to 3 ml of SB-16 solution and then stirring for 5 min at 298 K. Following this, to each of the prepared solutions the reducing agents DAF and DAH were added and their final concentrations was kept at 140 mM.…”

Vesicles Formation by Zwitterionic Micelle and Poly-l-lysine: Solvation and Rotational Relaxation Study

“…In general, the ζ value for 7 mM SB-16 micelle is about −12.7 mV due to the negative surface charge on the SB-16 micelle. Literaturereports also tells that SB-16 micelle carries negative charge on the surface of the aggregates 49,50. Upon addition of cationic PLL the negative charge of SB-16 decreases due to neutralization of the charge density and after vesicle formation with PLL the surface charge of these aggregates were almost saturated.…”

Amphiphile self-assembly based on ionic liquids

“…起到了电解质和共表面活性剂的作用, 从而促进了 Sarkar课题组 [106] Figure 11 Chemical structures of the acid/basic functional ILs [110] 羟基的引入影响不大. Lu等人 [111] 利用哌嗪类离子液…”