Micellization and interactions for ternary mixtures of amino sulfonate surfactant and nonionic octylphenol polyoxyethylene ethers in aqueous solution: 1 Blending with nonionic surfactants with smaller numbers of hydrophilic unit

The micellization and the molecular interactions for the ternary mixture of an amphoteric surfactant, sodium 3-(N-dodeyl ethylenediamino)-2-hydropropyl sulfonate (C12AS), with two nonionic surfactants, octylphenol polyoxyethylene ethers with different number (n) of oxyethylene glycol ethers (OP-n), e.g., OP-10 and OP-7, or OP-10 and OP-4, in aqueous solution were investigated by the tensiometry. Specifically, the effect of the addition of OP-7 or OP-4 on the micellization of binary mixture of C12AS/OP-10 was probed. The addition can decrease the value of mixed critical micellar concentration (cmc) and change the composition of mixed micelle. Thermodynamic data indicate that though the addition decreases the contribution of entropy to the process of micellization, its overwhelming effect is not changed, or in other words, the effect of the addition is relatively limited in this investigation. These findings may help with understanding the molecular interaction for the ternary surfactant mixture constituted by commercial surfactants, which are usually not single but the mixture of homologues. (C) 2019 Elsevier B.V. All rights reserved.