Interfacial processes polymer-modified electrodes

However, the interplay between electrolyte and polymer layer needs to be considered when optimizing the performances of polymer-modified electrodes. Structural factors will influence the interfacial ion transport and this will have a direct effect on the mechanism and location within the polymer layer of the mediation process. The following discussion will show that the nature of the mediation process can be changed dramatically by changing the electrolyte, from a situation where an electrochemical sensor with good sensitivity is obtained, to a situation where the sensitivity obtained is not much better than that observed for the bare electrode. 

Fig. 3.10a,b Schematics of the two models for polymer-modified electrodes, a Homogeneous model Zjf j/f, interfacial impedances (s f soIution fiIm f s film substrate), Zb impedance of the bulk phase, R -. solution resistance b porous (heterogeneous) model Z the impedance per unit length of the transport channel in the polymer phase, Z2 the impedance per unit length of the transport channel in the pores, Z3 the specific impedance at the iimer interface, which corresponds to charge transfer and charging processes, solution resistance. (From [68], reproduced with the permission of Elsevier Ltd.)... 

XPS of Polymer Surfaces Analytical Applications Radiation Damage Surface Modified Electrodes Interfacial Chemistry and Adhesion Surface Chemistry and Catalysis Mineralogy and Geochemistry Microelectronics Processing... 

Figure 3.9 illustrates the electrochemical and mass transport events that can occur at an electrode modified with a interfacial supramolecular assembly [9]. For monolayers in contact with a supporting electrolyte, the principal process is heterogeneous electron transfer across the electrode/monolayer interface. However, as discussed later in Chapter 5, thin films of polymers [10] represent an important class of interfacial supramolecular assembly (ISA) in which the properties of the redox center are affected by the physico-chemical properties of the polymer backbone. To address the properties of these thin films, mass transfer and reaction kinetics have to be considered. In this section, the properties of an ideally responding ISA are considered. 

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