Mixed micelles of cationic surfactants and bile acid salts in aqueous media

Abstract

Critical micelle concentrations of cetyltrimethylammonium-p-toluene sulfonate (CTAT) and cetylpyridinium chloride (CPC) with sodium cholate (NaC) and sodium deoxycholate (NaDC) were determined in aqueous solutions by surface tension measurements. Interaction parameters and mole fraction of the components in mixed micelles were estimated using Rubingh's theory. Strong interaction was observed for each mixed system, a common feature shown by anionic-cationic mixtures. Dramatic effects on the viscosities of these cationic surfactant-bile salt mixtures were seen, and were markedly dependent upon the counterion of the cationic surfactant and the nature of bile salts. Micelles are small and spherical for cationic surfactants in the presence of NaC. Micelle growth was seen for CPC in the presence of NaDC by an increase in viscosity, but a CTAT solution showed an opposite effect on addition of NaDC. Conductance results supported this view. Different behavior of the two bile salts is explained on the basis of their orientation in cationic micelles. JSD 1, 507-514 (1998). KEY WORDS:Ideal mixing, interaction parameter, mixed micelles, sodium cholate, sodium deoxycholate, synergism.Recently, much interest has been expressed in studying mixed surfactant systems both from basic and applied viewpoints (1,2). Usually, a marked interaction is observed, resulting in an increased cloud point, decreased Krafft point, increased surface activity, and decreased critical micelle concentration (CMC). Each change contributes favorably to practical applications of surfactants. Superiority in the performance of surfactant mixtures compared to single pure surfactants is often attributed to synergistic interactions among surfactants (1). Much research has focused on mixed systems comprised of anionic-anionic (3-6), cationic-cationic (7,8), anionic-cationic (9,10), ionic-nonionic (11), and nonionic-nonionic (12,13) surfactants. The CMC of surfactant mixtures composed of similarly structured ionic surfactants (14) or nonionic surfactants (14) can be predicted by assuming that they obey ideal solution theory in the micellar phase. The surface and bulk properties of aqueous solutions of oppositely charged surfactants and those of ionic and nonionic surfactants are often greater than expected for the other types of mixed systems. Mixed systems composed of anionic and cationic surfactants (15-19) often result in strong coulombic interaction with remarkably lower CMC in mixtures than expected for ideal mixing. This deviation from ideal behavior was successfully explained by Rubingh (20) using the phase separation model of micellization and regular solution approximation. However, in most cases the complex formed is generally insoluble in water (increased Krafft point), limiting the studies and applications of such systems. Although for anionic-cationic combinations a high probability of precipitation through charge neutralization at comparable ratio is present, when one component is in excess, stable mixed micelles are generally formed (21,22).Bile ...

Physicochemical Interactions of Chlorpheniramine Maleate with Sodium Deoxycholate in Aqueous Solution

“…, solutions having α CPM = 0.3, 0.5, 0.7, and 0.9 were turbid solutions. A similar observation was reported for different cationic + anionic surfactants (Barry and Gray, ; George et al, ; Jana and Moulik, ; Maiti et al, ; Maiti et al, ; Manna et al, ; Vethamuthu et al, ; Vethamuthu et al, ). It was reported that cetyltrimethylammonium chloride + SDC and cetyltrimethylammonium bromide (CTAB) + SDC with close to 0.5 mol fraction formed turbid mixtures, which led to phase separation upon standing over time (Barry and Gray, ; George et al, ; Vethamuthu et al, , ).…”

Precipitation and Micellar Properties of Novel Mixed Anionic Extended Surfactants and a Cationic Surfactant

“…As can be seen in Table 3, the b parameters for mixed monolayer formation and micelle formation are negative which means that all systems show synergism. These results are consistent with observations of other researches [20,[22][23][24] that the interactions between oppositely charged surfactant are strongly attractive due to the electrostatic forces between the two different hydrophilic head groups. Moreover, similar trends are also found in the interactions between two different surfactants in mixed micelles which are generally weaker than their interactions in mixed monolayers at the aqueous solutionair interface.…”

Mixed micelles of some metal dodecyl sulfates and triton X‐100 in aqueous media

“…The interaction between anionic-cationic surfactants is generally very strong, but such systems often lead to precipitation/coacervation due to the coulombic interactions between the oppositely charged species. We have recently reported studies on a few mixed surfactant systems composed of oppositely charged, similarly charged, and ionicnonionic surfactant systems (19,20). The results were in good agreement with those reported in the literature.…”

“…However, to our knowledge, few studies have documented anionic-nonionic mixed surfactant systems (11)(12)(13)19,21) despite considerable interaction being reported for these mixed systems. Besides, investigations demonstrating the influence of counter-ion valence on the interactions between surfactant molecules in the mixed micelle of the mixed surfactant system are scarce (8,18,20). Thus, investigating nonionic-anionic mixed surfactant systems with an emphasis on the influence of counter-ion valence on the nature and strength of interactions in these systems seemed worthwhile.…”