Solution properties of nonionic surfactants and their mixtures: Polyoxyethylene (10) alkyl ether [CnE10] and MEGA-10

The interfacial and thermodynamic properties of nonionic surfactants and th eir mixtures are of both theoretical and practical interest. The nonionic s urfactants used in this study are polyoxyethylene (10) alkyl ether [CnE10; m = 10 and n = 12, 16] and N-decanoyl-N-methylglucamine (MEGA-10). The crit ical micelle concentrations of pure surfactants and their mixtures were det ermined by surface tension measurements at different mixed ratios and tempe ratures. Interfacial parameters such as the maximum surface excess (Gamma(m ax)) and the minimum area per molecule (A(min)) at the air/water interface were also determined from surface tension data. Standard thermodynamic para meters of micellization and adsorption were also computed and discussed. St eady-state fluorescence studies were also carried out to determine the mice llar aggregation number (N-agg) and the microenvironment/polarity in the mi xed micelle from the I-1/I-3 ratio. The interaction parameters that measure the interaction between the surfactant molecules in the mixed micelle were computed by Rubingh's approach. H-1 NMR was also used to investigate the i nteraction between the surfactants.