Effect of hydrophobicity of zwitterionic surfactants and triblock polymers on their mixed micelles: A fluorescence study

The pyrene fluorescence measurements of various zwitterionic + triblock polymer surfactant mixtures have been carried out at 25 degrees C. From the variation of I1II3 intensity ratio of pyrene fluorescence, the critical micelle concentration (cmc) and other related micellar parameters of single and mixed surfactants have been determined. The nature of the mixed micelles has been evaluated with the help of regular solution and Motomura's approximations. It has been observed that the magnitude of synergistic mixing of zwitterionic and triblock polymer components in the mixed state is mainly governed by both the hydrophobicity of zwitterionic and triblock polymer components. The synergism reduces with an increase in the hydrophobicity of either of the two or both the components. The origin of synergistic interactions has been attributed to the cationic part of the polar head group repulsions by the intercalation of PEO units of triblock polymers. (c) 2005 Elsevier B.V. All rights reserved.