Surface conductivity reveals counterion condensation within grafted polyelectrolyte layers

Document Type

Article

Publication Date

2-8-2007

Abstract

Surface conductivity (SC) has been demonstrated to be a valuable parameter for the characterization of surface-bound polyelectrolyte layers (PLs). The measurement of the SC in dependence of the pH and solution concentration yields information about the Donnan potential, ΨD, the intrinsic charge, the potential of the PL electrolyte interface, Ψ0, the pK of the ionizable groups within the PLs, and the concentration of segments, n. We discuss herein that SC measurements may additionally provide information about counterion condensation. The mobility of the counterions within grafted poly(acrylic acid) (PAA) layers was estimated from the density of COOH groups and SC data to be only 14% of that of free ions (Zimmermann, et al. Langmuir 2005, 21, 5108). In view of this large deviation and the limited sterical constraints within the brushes, we conclude that the number of freely moving counterions is decreased due to counterion condensation. This interpretation agrees well with the measurement of the osmotic pressure for PAA solution (Boisvert, et al. Polymer 2002, 43, 141), which can be exclusively attributed to the remaining mobile counterions of the polyelectrolyte. © 2007 American Chemical Society.

Identifier

33847077651 (Scopus)

Publication Title

Journal of Physical Chemistry B

External Full Text Location

https://doi.org/10.1021/jp065585j

ISSN

15206106

First Page

979

Last Page

981

Issue

5

Volume

111

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