Influence of hydrophobicity on the mixed micelles of Pluronic F127 and P103 plus cationic surfactant mixtures

This study includes a systematic investigation of hydrophobic effect of conventional alkylammonium bromides and their dimeric homologues on the mixed micellization with (EO)97(PO)69(EO)97 (Pluronic F127), and (EO)17(PO)60(EO)17 (Pluronic P103). The steady state pyrene fluorescence has been measured for these binary mixtures over the whole mole fraction to determine the critical micelle concentration (cmc) and mean micelle aggregation number (Nagg). The data have been further evaluated by applying the regular solution theory (RST) and its extension suggested by Maeda [H. Maeda, J. Phys. Chem. B 108 (2004) 6043]. The evaluation of the micelle mole fraction demonstrates that the mixed micelles are mainly rich in the cationic component. The nature of the mixed micelles significantly depends on the degree of hydrophobicity of the cationic component.