Electrochemically Active Polyelectrolyte-Modified Electrodes

A polyelectrolyte solution contains the salt of a polyion, a polymer comprised of repeating ionized units. In dilute solutions, a substantial fraction of sodium ions are bound to polyacrylate at concentrations where sodium acetate exhibits only dissoci-atedions. Thus counterion binding plays a central role in polyelectrolyte solutions [1], Close approach of counterions to polyions results in mutual perturbation of the hydration layers and the description of the electrical potential around polyions is different to both the Debye-Huckel treatment for soluble ions and the Gouy-Chapman model for a surface charge distribution, with Manning condensation of ions around the polyelectrolyte. 

Coulombic, van der Waals, entropic and osmotic forces are coupled in a nontrivial way and give rise to important charge regulation in polyelectrolyte systems. The salt concentration is also an important factor to define the structure and thermodynamic properties of polyelectrolyte solutions. In weak polyelectrolytes the ionization equilibrium is also coupled to these interactions and thus the pKof ionizable groups depends on the organization of the interface and differs from that for the isolated molecule. 

Polyelectrolyte complexes formed by polyion pairing are of special interest, including protein-polyelectrolyte interactions such as protein-DNA complexes. A special case of polyelectrolyte complexes are polyelectrolyte multilayers (PEM) on surfaces formed by ion pairing, van der Waals interactions and counterion release of oppositely charged polyelectrolytes [2, 3]. 

In this chapter we describe the use of polyelectrolytes carrying redox-active centers on electrode surfaces with particular emphasis on organized layer-by-layer redox polyelectrolyte multilayers (RPEM). In redox-active polyelectrolyte multilayers the polyion-polyion intrinsic charge compensation can be broken by ion exchange driven by the electrochemical oxidation and reduction forming extrinsic polyion-counterion pairing. In this chapter we describe the structure, dynamics and applications of these systems. 

In the last 30 years considerable progress has been made in the development of tailor-made electrode surfaces by chemical modification [4-12] of electrodes surfaces with electroactive polymer films. A comprehensive description of electroactive polymer-modified electrodes can be found in the book edited by M. Lyons [13]. 

Advances in Electrochemical Science and Engineering Vd. 11 Chemically Modified Electrodes. Edited by Richard C. Alkire, Dieter M. Kolb, Jacek Lipkowski and Philip N. Ross Copyright 2009 WILEY-VCH Verlag GmbH Co. KGaA, Weinheim ISBN 978-3-527-31420-1 

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Electrochemically Active PolyelectrolYte-Modified Electrodes Table 2.2 (Continued) ... 

Tagliazucchi M, Calvo EJ (2009) Electrochemically active polyelectrolyte-modified electrodes. Adv Electrochem Sci Eng 11 57-115... 

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