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Counterion-only electrical double layer: A constrained entropy approach Wuge H. Briscoea)

Summary: Counterion-only electrical double layer: A constrained entropy approach
Wuge H. Briscoea)
Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, OX1 3QZ, Oxford,
United Kingdom
Phil Attardb)
Ian Wark Research Institute, University of South Australia, Mawson Lakes, SA 5095, Australia
Received 4 March 2002; accepted 21 June 2002
A counterion-only double-layer theory is developed taking a constrained entropy maximization
approach based on an isothermal thermodynamic system. The double-layer interaction free energy
per unit area between two charged planar surfaces is obtained in a consistent manner for the
boundary conditions of constant surface charge density and charge regulation. Once applied to the
nonpolar medium, it reveals that the electrical double-layer repulsion is weak and long-ranged.
Asymptotically, the interaction decays as a power law, in contrast with that in the presence of an ion
reservoir which decays exponentially at large surface separation. The applicability of the
counterion-only model for describing colloidal stability in nonpolar media is discussed. 2002
American Institute of Physics. DOI: 10.1063/1.1500359
The electrical double-layer interaction between charged
solid surfaces immersed in a liquid is of prominent impor-
tance in many circumstances of practical importance.1


Source: Attard, Phil - School of Chemistry, University of Sydney


Collections: Chemistry