MIXED MICELLES OF IONIC AND NONIONIC SURFACTANTS - QUASIELASTIC LIGHT-SCATTERING AND NMR SELF-DIFFUSION STUDIES OF C12E5-SDS MICELLES

Mixed micelles of C//1//2H//2//5(OCH//2CH//2)//5OH(C//1//2E//5) and C//1//2H//2//5OSO//3Na(SDS) have been studied by quasielastic light scattering and NMR self-diffusion. Over wide composition ranges, the light-scattering correlation function is distinctly bimodal with widely spaced decay times. The slow mode diffusion coefficients (10** minus **1**1-10** minus **1**2 m**2 sec** minus **1) are close to the self-diffusion coefficients obtained by the NMR method and are referred to the translational motion of the micelles. The fast mode (2-3 multiplied by 10** minus **1**0 m**2 sec** minus **1) is interpreted as a collective mode involving strong electrostatic interactions. Micelle size varies strongly when the SDS content is varied and this is discussed in terms of electrostatic head group repulsions and steric packing restrictions.