Intrinsic charge and Donnan potentials of grafted polyelectrolyte layers determined by surface conductivity data

Document Type

Article

Publication Date

6-1-2004

Abstract

In order to characterize grafted polyelectrolyte layers based on electrokinetic measurements a theory of the surface conductivity K σ was developed, starting from the model of thick polyelectrolyte layers with uniform segment distribution and dissociable groups with an unknown pK value. According to this model the inner part of the polyelectrolyte layer adjacent to the substrate is considered to be isopotential while the potential decay occurs in a zone near the solution side of the layer. A simple equation for the Donnan potential ΨD as a function of pH, pK, electrolyte concentration C0, and volume charge density ρ was obtained. In the derived equation Kσ is directly related to ΨD, while the other terms have less influence on the magnitude of Kσ and can be accounted for in a second approximation using ΨD as determined from the measured Kσ. Evaluation of the suggested model indicates that Kσ measurements provide an effective method to characterize polyelectrolyte layers by analyzing the dependence of ΨD on pH and C0: The magnitude of Kσ yields information about the surface charge at complete dissociation of the ionizable groups. The dependence of K σ on pH and C0 can be used for the determination of the pK value of the dissociating functions and the segment volume fraction of the polyelectrolyte can be estimated using the measured value of ρ.

Identifier

2042514989 (Scopus)

Publication Title

Journal of Colloid and Interface Science

External Full Text Location

https://doi.org/10.1016/j.jcis.2003.11.016

ISSN

00219797

First Page

309

Last Page

318

Issue

1

Volume

274

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