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 $10\ensuremath{\le}t\ensuremath{\lesssim}{10}^{3}$ s and quench depths from 0.7 to 9 mK. The parameters measured were ${k}_{m}(t)$, 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 ${k}_{m}\ensuremath{\propto}{t}^{\ensuremath{-}\ensuremath{\phi}}$, with $\ensuremath{\phi}=\frac{1}{3}$. In the late stage $\ensuremath{\phi}$ increases to unity in both systems. This implies that hydrodynamic effects control the rate of growth of the nucleating domains of size $l\ensuremath{\simeq}{k}_{m}^{\ensuremath{-}1}$. In both early and late stages, the intensity measurements are consistent with $I({k}_{m},t)\ensuremath{\propto}{l}^{3}$. The scattering experiments were supplemented by direct observation of domain growth with a microscope.