Phase Separation in Mixtures of Nematic and Isotropic Fluids

Mixtures of nematic liquid crystals and isotropic fluids present a rich platform to explore the interplay between orientational order and concentration fluctuations, both experimentally and theoretically. These systems exhibit a wealth of phase behaviors and interfacial phenomena, shaped by the coupling of thermodynamic and kinetic effects. In this review, we present a unified theoretical framework that combines the Landau–de Gennes free energy for nematic ordering with the Cahn–Hilliard description of phase separation. This minimal model captures a wide range of characteristic behaviors, from phase separation and spinodal decomposition to the emergence of anisotropic domains and defect structures driven by the competition between interfacial anchoring and elastic interactions. We analyze the stability of the uniform isotropic and nematic phases and the phase separation dynamics and the interfacial behaviors that arise, and we reference the role of hydrodynamic interactions. The scope is further broadened by reference to active nematic emulsions, in which internal stresses drive nonequilibrium dynamics and novel steady states. Together, these phenomena underscore the versatility of nematic–isotropic mixtures as model systems in soft condensed matter physics.