27 July 2004 Understanding ion transport in conjugated polymers
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Electron transport and ion transport are two critical processes taking place during electrochemical oxidation/reduction of conjugated polymers. Because they accompany and depend on each other, research on the individual processes is difficult. We present a device that allows us to measure ion transport directly and independently from electron transport in conjugated polymers. The device geometry makes the ion path much longer than the electron path, ensuring that ion transport is the rate-limiting step. Ion transport is also visualized directly through the color change of the film (electrochromism) as the electrochemical reaction proceeds, allowing one to precisely and quantitatively track the ion velocity. During reduction at sufficiently negative potentials, a phase front between the oxidized and reduced states was observed to travel into the film, the speed of which was proportional to the applied voltage, demonstrating that migration (rather than diffusion) is the key driving force. At less negative reducing potentials, the film gradually and more uniformly changed color, indicating that diffusion plays a large role. A simple first-cut model with drift and diffusion terms is presented. The simulated ion concentration profile matched the experimentally measured intensity profile strikingly well.
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Xuezheng Wang, Xuezheng Wang, Elisabeth Smela, Elisabeth Smela, Benjamin Shapiro, Benjamin Shapiro, } "Understanding ion transport in conjugated polymers", Proc. SPIE 5385, Smart Structures and Materials 2004: Electroactive Polymer Actuators and Devices (EAPAD), (27 July 2004); doi: 10.1117/12.541546; https://doi.org/10.1117/12.541546


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