Phase-separation of miscible liquids in a centrifuge

Abstract

We show that a liquid mixture in the thermodynamically stable homogeneous phase can undergo a phase-separation transition when rotated at sufficiently high frequency $\omega$. This phase-transition is different from the usual case where two liquids are immiscible or where the slow sedimentation process of one component (e.g. a polymer) is accelerated due to centrifugation. For a binary mixture, the main coupling is due to a term $\propto \Delta \rho (\omega r{)}^2$, where $\Delta \rho$ is the difference between the two liquid densities and $r$ the distance from the rotation axis. Below the critical temperature there is a critical rotation frequency ${\omega }_c$, below which smooth density gradients occur. When $\omega >{\omega }_c$, we find a sharp interface between the low density liquid close to the center of the centrifuge and a high density liquid far from the center. These findings may be relevant to various separation processes and to the control of chemical reactions, in particular their kinetics.

6 pages, 3 figures

References in corpus (2)

• Phase-separation in ion-containing mixtures in electric fields
• Lamellar Phases in Nonuniform Electric Fields: Breaking the In-Plane Rotation Symmetry and the Role of Dielectric Constant Mismatch

Cited by in corpus (2)

• Phase-Separation Transition in Liquid Mixtures Near Charged Objects
• Phase lines in mean-field models with nonuniform external forces