Critical behavior of a colloid-polymer mixture confined between walls

Abstract

We investigate the influence of confinement on phase separation in colloid-polymer mixtures. To describe the particle interactions, the colloid-polymer model of Asakura and Oosawa [J. Chem. Phys. 22, 1255 (1954)] is used. Grand canonical Monte Carlo simulations are then applied to this model confined between two parallel hard walls, separated by a distance D=5 colloid diameters. We focus on the critical regime of the phase separation and look for signs of crossover from three-dimensional (3D) Ising to two-dimensional (2D) Ising universality. To extract the critical behavior, finite size scaling techniques are used, including the recently proposed algorithm of Kim et al. [Phys. Rev. Lett. 91, 065701 (2003)]. Our results point to effective critical exponents that differ profoundly from 3D Ising values, and that are already very close to 2D Ising values. In particular, we observe that the critical exponent beta of the order parameter in the confined system is smaller than in 3D bulk, yielding a flatter binodal. Our results also show an increase in the critical colloid packing fraction in the confined system with respect to the bulk. The latter seems consistent with theoretical expectations, although subtleties due to singularities in the critical behavior of the coexistence diameter cannot be ruled out.

12 pages, 10 figures

References in corpus (3)

• Capillary Waves in a Colloid-Polymer Interface
• The fluid-fluid interface in a model colloid-polymer mixture: Application of grand canonical Monte Carlo to asymmetric binary mixtures
• Critical phenomena in colloid-polymer mixtures: interfacial tension, order parameter, susceptibility and coexistence diameter

Cited by in corpus (10)

• Fluids in Extreme Confinement
• Statics and Dynamics of Colloid-Polymer Mixtures Near Their Critical Point of Phase Separation: A Computer Simulation Study of a Continuous AO Model
• Depletion induced isotropic-isotropic phase separation in suspensions of rod-like colloids
• Phase diagram and structure of colloid-polymer mixtures confined between walls
• Effect of excluded volume interactions on the interfacial properties of colloid-polymer mixtures
• Colloid-polymer mixtures in random porous media: Finite size scaling and connected versus disconnected susceptibilities
• From Capillary Condensation to Interface Localization Transitions in Colloid Polymer Mixtures Confined in Thin Film Geometry
• Structural quantities of quasi-two-dimensional fluids
• Phase separation of an asymmetric binary fluid mixture confined in a nanoscopic slit pore: Molecular-dynamics simulations
• Liquid-vapor critical behavior of the TIP4P/2005 water model: effects of NaCl solutes and hydrophobic confinement