Enhancement of the Solubilization Capacity of Water in Triton X‐100/Cyclohexane/Water System by Compressed Gases

Abstract

The effect of compressed CO2 and ethylene on the properties of Triton X-100/cyclohexane/water systems was studied at different temperatures and pressures. Surprisingly, it was discovered that the compressed gases had the functions of co-surfactants. At suitable pressures, the water-to-surfactant molar ratio (W0) was enhanced significantly by the dissolution of the gas in the solution. The microenvironment in the reverse micelles was investigated by UV-visible spectroscopy by using methyl orange (MO) as a probe. The influence of n-hexane, Na2CO3, NaHCO3, H2C2O4, and CaCl2 at various concentrations on the solubilization of water in the absence of compressed gases was also investigated in order to obtain some information about the mechanism of the interesting phenomenon. This new route to stabilize reverse micelles may have potential applications to other similar systems. Moreover, the results of this work provide some useful information to get insight into the mechanism of co-surfactants, because a conventional co-surfactant usually contains both polar group and hydrocarbon chain, and it is very difficult to clarify the functions these two groups, while the gases used in this work are small nonpolar molecules, which solely have the function of the hydrocarbon chain in a co-surfactant.

Effect of Compressed CO2 on the Critical Micelle Concentration and Aggregation Number of AOT Reverse Micelles in Isooctane

“…The reason is that CO 2 can penetrate into the interfacial film of the reverse micelles and stabilize them by increasing the rigidity of the micelle interlayer, thus reducing the attractive interaction between the droplets. [39] Interestingly, the X CO 2 value corresponding to the minimum cmc point in Figure 3 is consistent with the X CO 2 value at which the w 0 max value occurs. We can deduce that CO 2 in the solution affects the cmc value in two opposite ways.…”

“…[36][37][38] Our previous work showed that compressed CO 2 and ethylene can increase the solubilization capacity of water in sodium bis-2-ethylhexylsulfosuccinate (AOT) and Triton X-100 reverse-micellar systems at suitable pressures because the gases can insert into the interfacial region to enhance the rigidity of the interface layers and reduce the interdroplet attraction. [39][40][41] The tuning and control of the properties of micellar solutions with compressed CO 2 is a very interesting topic. The critical micelle concentration (cmc) and aggregation number are two of the most important characteristics of reverse-micellar solutions.…”

Phase behaviors of AOT/longer chain n-alkanes reverse micelles in the presence of compressed ethylene

“…Because the presence of salinity in the micelle cores can vary the attractive interdroplet interaction and interfacial bending stress [4], it is difficult to distinguish whether the increase of salinity that originates from ionization of CO 2 is a main reason or not for stabilization of the reverse micelles. Generally, the solubility of ethylene in water is extremely small under moderate conditions because of the significant difference in structure and polarity of water and ethylene [14][15][16], while ethylene can increase the solubility of water in a nonionic surfactant (TX-100) reverse micellar system [17]. In this paper, we investigated the effect of compressed ethylene on the solubilization capacity of water in the reverse micelles of AOT in longer-chain alkanes, and the microenvironments of the reverse micelles in the presence of the compressed gas were studied by conductivity measurement and UV-vis technique.…”

Reversible Switching of a Micelle‐to‐Vesicle Transition by Compressed CO2

“…Compressed CO 2 has been used in different fields, such as extraction and fractionation, [12] chemical reactions, [13] materials science, [14] microelectronics, [15] and for the control over the stability of micelles [16] that inhibit the precipitation of surfactants in vesicular systems, [17] the induction of nanoemulsions, [18] the transition between liquid crystals and micelles, [19] the creation of micro-…”