ISSN:
1435-1536
Keywords:
Donnan model
;
Donnan potential
;
polyelectrolyte
;
counterion binding
;
potential distribution
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
,
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Abstract The validity of the macroscopic Donnan model for polyelectrolytes in an electrolyte solution is examined by taking into account the effects of the varying potential distribution across the boundary between a polyelectrolyte and the surrounding solution, using the composite Poisson-Boltzmann equations for the polyelectrolyte interior and the surrounding solution. Calculations are made for a planar polyelectrolyte of thickness 2d and a planar polyelectrolyte layer of thicknessd covering a rigid surface, both showing the identical potential distribution. A simple expression for a correction factor for these effects is derived which enables to evaluate various corrected quantities in the polyelectrolyte interior such as the average potential, the average ionic concentration, the average degree of dissociation and the apparent dissociation constant of ionizable groups in the polyelectrolyte. It is found that when κd≪1 (where κ indicates the Debye-Hückel parameter) the macroscopic Donnan model can safely be applied, while as κd decreases the effects of the varying potential distribution become appreciable.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00652421
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