Demixing and field-induced population inversion in a mixture of neutral and dipolar-hard spheres confined in a slit pore

Phase Behavior of Magnetic Nanocolloids of Different Sizes Suspended in an Apolar Solvent

“…To analyze this effect quantitatively, we follow the work of Verschaffelt 39 and introduce a (nonuniversal) effective critical exponent (35) where Δρ ≡ ρ″ − ρ′ along the GI portion of the coexistence curve and τ ≡ 1 − T/T c is a measure of the "distance" from the GI critical point. Clearly, sufficiently close to the GI critical point (in the limit τ → 0), one has to expect that ρ τ Δ ∝ β (36) where β = 1 2 is the classical (mean-field) exponent. 50 This conclusion is based upon the fact that our expression for the excess free energy [cf.…”

“…Although many studies have examined binary mixtures, relatively few theoretical works exist in which one or both components can form ordered phases. For example, Ising mixtures composed of a ferromagnetic and a nonmagnetic compound have been investigated; in other works, mixtures of dipolar spheres of different dipolar coupling strengths − as well as binary mixtures composed of dipolar and apolar spheres have been considered. ,− Properties of these systems and, in particular, their possibility to phase separate have important repercussions for the stability of colloidal suspensions; the tendency of binary mixtures of nanoparticles and macromolecules to undergo phase separation is relevant for understanding novel and exciting phenomena such as Casimir forces …”

Wall–particle interactions and depletion forces in narrow slits

“…The phase separation of the NASH model was also studied for symmetric binary mixtures with different composition (σ a = σ b and Δ N 0) under confinement [53] leading to the so called population inversion effect [54] (clearly related to the capillarity condensation/evaporation phenomenon). It consists on that, under certain conditions, the more concentrated bulk species turns the less concentrated species inside the pore [55,56]. The departure from the ideal behavior of polymer coils (σ p N 0) reduces the adsorption of colloids on the walls.…”