Phase separation and coalescence in critically quenched isobutyric-acid—water and 2,6-lutidine—water mixtures

Abstract

Light scattering was used to study phase separation in critically quenched mixtures of isobutyric-acid—water and 2,6-lutidine—water. The measurements spanned the time interval $10\le t\lesssim {10}^3$ s and quench depths from 0.7 to 9 mK. The parameters measured were $k_m\mathrm{}\left(t\right)\mathrm{}$, i.e., the photon momentum transfer at the angle of maximum scattering, and the ring intensity $I(k_m,t)$. The early-stage measurements of $k_m$ vs $t$ are in very good agreement with the calculations of Kawasaki and Ohta and with the coalescence model of domain growth, which gives $k_m\propto t^{-\varphi }$, with $\varphi =\frac{1}{3}$. In the late stage $\varphi$ increases to unity in both systems. This implies that hydrodynamic effects control the rate of growth of the nucleating domains of size $l\simeq k_m^{-1\mathrm{}}$. In both early and late stages, the intensity measurements are consistent with $I(k_m,t)\propto l^3$. The scattering experiments were supplemented by direct observation of domain growth with a microscope.