A study of the microscopic structure of mixed cationic/nonionic micelles by NMR and time-resolved fluorescence spectroscopy

The structure of mixed cationic/nonionic micelles of hexadecyltrimethylammonium chloride (CTACl) and Triton X100 (TX100) was studied at the molecular level using both NMR and fluorescence measurements. In rich CTACl mixtures, the physical properties (intramicellar viscosity, polarity) of mixed micelles are similar to those of the CTACl micelles. The peculiar structure of TX100 micelles proposed by Robson and Dennis (J. Phys. Chem., 81 (1977) 1075) seems to be broken for mole fractions higher than 0.33. In rich TX100 medium and at low CTACl content, an interaction between the quaternary ammonium group of CTACl and the phenyl ring of TX100 has been shown. In these mixtures, the mixed micellar structure are close to the TX100 one.