Solution structure of nonionic surfactant microemulsions from nuclear magnetic resonance self-diffusion studies

Abstract

Self-diffusion studies were performed to obtain insight into the aggregate structure of the various isotrophic solutions in nonionic surfactant-hydrocarbon-water systems often referred to as microemulsions. The systems chosen were tetraethylene glycol dodecyl ether-decane-water, and tetraethylene glycol decyl ether-hexadecane-water. Self-diffusion coefficients were determined for all components by means of the nuclear magnetic resonance spin-echo pulsed field gradient method. From a comparison of the self-diffusion coefficients of the different components, conclusions can be drawn about solution structure in the different isotropic regions. For the systems studied, the isotropic water-rich and hydrocarbon-rich phases are connected in a composition-temperture diagram by an isotropic channel, the surfactant phase. In the surfactant phase there is rapid diffusion of both water and hydrocarbon. 36 references.