Redox mediation at electroactive polymer coated electrodes: Mechanistic diagnosis criteria from steady state polarization curves

Exploiting mixed conducting polymers in organic and bioelectronic devices

Efficient transport of both ionic and electronic charges in conjugated polymers (CPs) has enabled a wide range of novel electrochemical devices spanning applications from energy storage to bioelectronic devices. In this Perspective, we provide an overview of the fundamental physical processes which underlie the operation of mixed conducting polymer (MCP) devices. While charge injection and transport have been studied extensively in both ionic and electronic conductors, translating these principles to mixed conducting systems proves challenging due to the complex relationships among the individual materials properties. We break down the process of electrochemical (de)doping, the basic feature exploited in mixed conducting devices, into its key steps, highlighting recent advances in the study of these physical processes in the context of MCPs. Furthermore, we identify remaining challenges in further extending fundamental understanding of MCP-based device operation. Ultimately, a deeper understanding of the elementary processes governing operation in MCPs will drive the advancement in both materials design and device performance.

Responsive organometallic polymer grafts: electrochemical switching of surface properties and current mediation behavior

Quantitative adherence and friction measurements between atomic force microscopy (AFM) tips and reversibly oxidized and reduced poly(ferrocenyl dimethylsilane) (PFDMS) molecular layers grafted to Au are reported. Poly(ferrocenylsilanes) (PFSs) such as PFDMS owe their redox responsiveness to the presence of ferrocene units, bridged by substituted silicon units, in the main chain. Polymers were obtained by anionic polymerization, which allowed us to copolymerize sulfur containing end groups that facilitated grafting to Au surfaces. Electrochemical atomic force microscopy (ECAFM) was used to study adherence and friction as a function of the oxidation state of the polymer. Measurements of interfacial friction as a function of applied load on the nanoscale using Si(3)N(4) AFM tips revealed a reversible increase of the friction coefficient and adherence strength of the PFDMS layers with increasing oxidation state in NaClO(4) electrolytes. The variation of the electrolyte salts (NaClO(4) or NaNO(3)) allowed an assessment of surface counterion adsorption effects. Issues related to the interpretation of observed friction and adherence changes such as electrolyte anion-ferrocenium ion pair effects, and electrostatic forces due to tip surface charges are discussed. Unidirectional current flow was detected in cyclic voltammograms of the PFDMS layers in NaClO(4). This electrode rectification behavior could in principle be utilized for applications in thin film devices based on PFS films.