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Authors
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Dukhin, St. ; Zimmermann, R. ; Werner, C.
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Title
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Intrinsic Charge and Donnan potentials of grafted polyelectrolyte layers determined by surface onductivity data
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Date
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18.06.2004
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Number
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11674
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Abstract
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In order to characterize grafted polyelectrolyte layers based on electrokinetic measurements a theory of the surface conductivity <i>K</i><sup>σ</sup> was developed, starting from the model of thick polyelectrolyte layers with uniform segment distribution and dissociable groups with an unknown p<i>K</i> 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 Ψ<sub><i>D</i></sub> as a function of pH, p<i>K</i>, electrolyte concentration <i>C</i><sub>0</sub>, and volume charge density ρ was obtained. In the derived equation <i>K</i><sup>σ</sup> is directly related to Ψ<sub><i>D</i></sub>, while the other terms have less <br />influence on the magnitude of <i>K</i><sup>σ</sup> and can be accounted for in a second approximation using Ψ<sub><i>D</i></sub> as determined from the measured <i>K</i><sup>σ</sup>. Evaluation of the suggested model indicates that <i>K</i><sup>σ</sup> measurements provide an effective method to characterize polyelectrolyte layers by analyzing the dependence of Ψ<sub><i>D</i></sub> on pH and <i>C</i><sub>0</sub>: The magnitude of <i>K</i><sup>σ</sup> yields information about the surface charge at complete dissociation of the ionizable groups. The dependence of <i>K</i><sup>σ</sup> on pH and <i>C</i><sub>0</sub> can be used for the determination of the p<i>K</i> value of the dissociating functions and the segment volume fraction of the polyelectrolyte can be estimated using the measured value of ρ.
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Publisher
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Journal of Colloid and Interface Science
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Wikidata
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Citation
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Journal of Colloid and Interface Science 274 (2004) 309-318
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DOI
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https://doi.org/10.1016/j.jcis.2003.11.016
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Tags
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MBC_Electrosurface_Analysis
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