Structural evolution and microscopic interactions in a three-component amphiphilic microemulsion system

Structures and interaction parameters of a three-component amphiphilic microemulsion system consisting of n-decane, water, and an amphiphile AOT (sodium-di-2-ethylhexylsulfosuccinate) have been studied by means of small angle neutron scattering. The scattering curves are fitted with Teubuer and Strey’s formula, from which three structural parameters are extracted; the average periodic distance D between the oil and water, the structural correlation length ξ, and the area aH per amphiphile molecule. The same data are further examined in terms of Gompper and Schick’s formula, from which three interaction parameters are obtained; the strength of segregation J/T among the oil and water, the amphiphilicity L/T of the amphiphile toward the oil and water, and the critical surfactant volume fraction φcs. These interaction parameters have right order of magnitudes and their implications to structural evolution are discussed.