Visualizing the electric field in electrolytes using electrochromism from a conjugated polymer

Electrochromic polymer films, employed as display elements, smart windows, and the base material for electrochemical electronic devices, can be addressed solely through ionic transport via an electrolyte, without direct electronic connection as typically employed in the above examples. We present a demonstration of induced electrochromism to quantify the direction and magnitude of the electric field in an electrolyte using poly(3,4-ethylenedioxythiophene) doped with polystyrene-sulfonate. After further development, this simple yet effective technique will be potentially applicable for optimizing batteries and fuel cells, as the active detection element in electrochemical sensors and as a detector in ionic separation in electrolytes (electrophoresis). (C) 2004 The Electrochemical Society.