Critical Scaling Behavior of Microemulsion Systems

Abstract

Abstract We used dynamic light scattering to study the characteristic droplet size, r̄, in dilute single-phase microemulsions near the critical phase transition point. We found that there existed a general power-law dependence of r̄ on the reduced variable ΔZ=Zc−Z. Here Z stands for any thermodynamic and system variables whose critical value is denoted by Zc. The variables of interest in the present work are temperature and alkane carbon number (ACN). It is found that r̄∝ΔZ−ν where ν =0.75±0.1. This is observed both in water- and oil-internal microemulsions, independent of the surfactant properties. This behavior, known as the scaling behavior, was analyzed in terms of generalized homogeneous functions with v as the degree of homogeneity. It turns out that only one of the reduced variables is an independent variable in these functions, greatly simplifying the description of the properties of microemulsions in the neighborhood of a critical phase boundary.