On the fluid-fluid phase separation in charged-stabilized colloidal suspensions

• Published in: arXiv.org
• Main Authors: Levin, Yan, Trizac, Emmanuel, Bocquet, Lyderic
• Format: Paper
• Language: English
• Published: Ithaca Cornell University Library, arXiv.org 12.01.2004
• Subjects: Colloids; Computer simulation; Deionization; Dependence; Electrolytes; Equations of state; Jellium; Monte Carlo simulation; Phase separation; Phase transitions; Stability
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.0401175

We develop a thermodynamic description of particles held at a fixed surface potential. This system is of particular interest in view of the continuing controversy over the possibility of a fluid-fluid phase separation in aqueous colloidal suspensions with monovalent counterions. The condition of fixed surface potential allows in a natural way to account for the colloidal charge renormalization. In a first approach, we assess the importance of the so called ``volume terms'', and find that in the absence of salt, charge renormalization is sufficient to stabilize suspension against a fluid-fluid phase separation. Presence of salt, on the other hand, is found to lead to an instability. A very strong dependence on the approximations used, however, puts the reality of this phase transition in a serious doubt. To further understand the nature of the instability we next study a Jellium-like approximation, which does not lead to a phase separation and produces a relatively accurate analytical equation of state for a deionized suspensions of highly charged colloidal spheres. A critical analysis of various theories of strongly asymmetric electrolytes is presented to asses their reliability as compared to the Monte Carlo simulations.