Mixed Micellization and the Dissociated Margules Model for Cationic/Anionic Surfactant Systems

Abstract

The first and the second critical micelle concentration (CMC(1) and CMC(2)) for three alkyltrimethylammonium bromide (C(n)TAB)/sodium dodecylsulfonate (AS)/H(2)O mixed systems, and CMC(1) for trimethylene-1,3-bis(dodecyldimethylammonium bromide) (12-3-12)/AS/H(2)O mixed system have been measured. The largest negative β(m) value means the strongest synergism between 12-3-12 and AS. The CMC(1) and CMC(2) for the C(n)TAB/AS/H(2)O mixed systems decrease with the increase of n. The equimolar mixed systems give the smallest CMC(1) values, whereas the CMC(2) values decrease with the increase of the composition of the surfactant with higher surface activity in the C(n)TAB/AS/H(2)O mixed systems. For the C(16)TAB/AS mixed systems far from equimolar, specific counterion effect on lowering CMC(1) enhances according to the Hofmeister series. There is slightly or no salt effect on the CMC(1) of the other wide composition range of C(16)TAB/AS/H(2)O mixed system. The pseudophase separation model coupled with the dissociated Margules model has been proposed and gives satisfactory description of the mixed CMC(1), the calculated micellar compositions are in well accordance with composition information from the ζ potential measurements. The addition of salt into the C(16)TAB/AS/H(2)O mixed system, leads to a certain degree of decrease in CMC(2). In addition to counterion effect, the co-ion effect on CMC(2) of the mixed system was explained using Collins' concept of matching water affinities.

Effect of surfactant head group on micellization and morphological transitions in drug-Surfactant catanionic mixture: A multi-technique approach

“…In equations (2) and (3) region followed by decrease in magnitude when concentration exceeds equimolarity which can be attributed to the steric hindrance offered by more TC molecules as earlier reported in many catanionic mixtures [36][37][38][39][40]. But at αTC = 0.9 in case of TC + SDBS, the highest β m value were found to be present when which might be due to the reason that more TC molecules orient the bulkier headgroups of SDBS molecules in such a array that they release the TC molecules and reduces repulsive interactions there.…”

Molecular array behavior and synergistic effect of sodium alcohol ether sulphate and carboxyl betaine/sulfobetaine in foam film under high salt conditions

“…Most of the literatures about the synergistic effect of the mixed surfactants focused on the mixture of nonionic/ionic surfactants and amphoteric/ionic surfactants [12][13][14][15][16][17][18][19]. It has been reported that the co-adsorption of non-ionic/ionic surfactants or amphoteric/ionic surfactants on the gas/water or oil/water interfaces could improve the interfacial activity significantly by reducing the electrical repulsion between the charged head groups and increasing the interfacial density of the adsorbed molecules [20,21].…”

Role of matching water affinities between oppositely charged headgroups in the rheological properties of aqueous mixed cationic/anionic surfactant systems

“…This is in line with the well-known fact that water molecules take an essential part within micelle structure particularly at Stern layer that containing amphiphilic headgroups, indicating that the hydration of headgroups is an important factor influencing the molecular packing of surfactant in micelles [43]. For 0.10 mol kg −1 CTAB aqueous solution, rodlike micelles form spontaneously since the second critical micelle concentration (CMC 2 ) at which the micelles undergo structural transition from spherical to rodlike micelles is 20.68 mmol L −1 at 318.15 K [45], thus p is in the range between 1/3 and 1/2. With the gradual addition of AS into CTAB solution, electrostatic attraction between oppositely charged headgroups and the hydrophobic interaction between their tail chains lead to the formation of mixed micelles.…”