Small-angle neutron-scattering studies of microemulsions stabilized by aerosol-OT. Part 2.—Critical scattering and phase stability

Abstract

Small-angle neutron scattering has been used to characterise the structural properties of various microemulsions containing D₂O water droplets, stabilised by the surfactant aerosol-OT in decane, undecane and dodecane solvents. Phase diagrams have also been obtained for corresponding systems containing H₂O. The SANS intensity profile exhibits a critical scattering component in the low-Q region which increases in magnitude as the temperature approaches the limit of stability. The observations may be fitted to an Ornstein–Zernike expression to determine a correlation length ξ, and this is found to vary systematically with respect to the reduced temperature difference ε=(T_c–T)/T_c. The critical constants v and γ are found to be 0.67±0.10 and 1.65±0.15, respectively.