Mixed micelles of cationic–nonionic surfactants: NMR self-diffusion studies of Triton X-100 and cetyltrimethylammonium bromide in aqueous solution

The Fourier transform pulsed-field-gradient NMR technique has been used to measure the self-diffusion coefficients of the two surfactants cetyltrimethylammonium bromide (CTAB) and Triton X-100 (TX-100) in their mixed aqueous solutions with various molar ratios of CTAB to TX-100. Through simulating these experimental values of the self-diffusion coefficients by the two-state exchange model, some important dynamical micellization parameters, such as the critical micellar concentration of each soltute, the critical mixed micellar concentration and the self-diffusion coefficient of the mixed micelles at various molar ratios have been obtained. The composition of the mixed micelles and the interaction parameters between the two surfactants have also been evaluated. The mixed-micellization processes were discussed on the basis of these parameters. The results demonstrate the advantages of using NMR self-diffusion measurements to study binary cationic–nonionic mixed systems.