Free-standing polypyrrole fi lms, being the metal-polymer contact located several millimeters outside the electrolyte, give stationary closed coulovoltammetric (charge/potential) loop responses to consecutive potential sweeps from -2.50 V to 0.65 V in aqueous solutions. The continuous and closed charge evolution corroborates the presence of reversible fi lm reactions (electroactivity), together high electronic and ionic conductivities in the full potential range. The closed charge loop demonstrates that the irreversible hydrogen evolution is fully inhibited from aqueous solutions of different salts up to -2.5 V vs Ag/AgCl. The morphology of the closed charge loops shows abrupt slope changes corresponding to the four basic components of the structural electrochemistry for a 3D electroactive gel: reduction-shrinking, reduction-compaction, oxidation-relaxation, and oxidation-swelling. Freestanding fi lms of conducting polymers behave as 3D gel electrodes (reactors) at the chain level, where reversible electrochemical reactions drive structural conformational and macroscopic (volume variation) changes. Very slow hydrogen evolution is revealed by coulovoltammetric responses at more cathodic potentials than -1.1 V from strong acid solutions, or in neutral salts self-supported blend fi lms of polypyrrole with large organic acids. Conducting polymers overcome graphite, mercury, lead, diamond, or carbon electrodes as hydrogen inhibitors, and can compete with them for some electro-analytical and electrochemical applications in aqueous solutions.
The coulo‐dynamic (angle/consumed charge) characterization of an asymmetric polypyrrole (PPy) bending bilayer (PPy1/PPy2) muscle is performed in aqueous solutions by cyclic voltammetry with parallel video recording of a reversible angular displacement of 200°. The characterization of each of the two PPy1/tape, PPy2/tape muscles, describing 30° and 50° per voltammetric cycle, corroborates the driven muscle reactions and ionic exchanges. The asymmetric bilayer efficiency, as described degrees per reaction unit, is seven and four times that of the PPy/tape muscles. A cooperative electro‐chemo‐mechanical actuation of each of the individual layers occurs in the asymmetric bilayer. Each of the three muscles is a Faradaic polymeric motor: described angles are linear functions of the consumed charge with small hysteresis loops. Each loop is related to dynamic water osmotic balance following the reaction driven film swelling or its fast electro‐osmotic expulsion around the reduction induced conformational closing and film compaction.
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