Understanding Ion Transport in Conjugated Polymers
Abstract
Ion transport is critical to improving the performance of conjugated polymer actuators, particularly their strain and speed. We present a novel device that allows us to measure ion transport directly and independently from electron transport in PPy films. The device geometry makes the path for ions much longer than that for electrons, ensuring that ion transport is the rate-limiting step. In addition, ion transport is visualized directly though the change in color of the film (electrochromism) as the electrochemical reaction proceeds, allowing us to precisely and quantitatively track the ion velocity. For high applied voltages, a phase front between oxidized and reduced states is observed to travel into the film, the speed of which is proportional to the applied voltage, which conclusively demonstrates that migration is the key driving force. The phase front broadens with time, which we hypothesize to be due to difflision. At lower applied voltages, there is no phase front, showing that diffusion is the rate-limiting process. A first-cut model that contains diffi%sion and drift terms is postulated, and the simulation results are compared with the experimental data. This simple model predicts the intensity profiles strikingly well.
Document Details
- Document Type
- Technical Report
- Publication Date
- Feb 10, 2004
- Accession Number
- ADA425255
Entities
People
- Benjamin Shapiro
- Elisabeth Smela
- Xuezheng Wang
Organizations
- University of Maryland