Controlled Continuous Production of Conducting Polypyrrole Tapes I: Process Control Development

Abstract

A common method for the synthesis of conducting polypyrrole involves the use of potentiostatic or galvanostatic deposition. The electrical and mechanical properties of the polymer resulting from these synthesis techniques are known to be highly dependent on a number of factors. These factors include the reactant and electrolyte concentrations and other conditions, such as pH. During batch synthesis these parameters have been observed to vary, so that the electrodeposited polypyrrole film is affected by continually changing chemical environments. As a result, polymeric material with different properties is deposited on top of the polymer formed earlier during synthesis. This problem is further exacerbated when polypyrrole is synthesized on a continuous basis using a rotating anode electrode. In order to avoid these effects a process control system has been developed to monitor and control these critical parameters for both batch and continuous electrochemical synthesis of polypyrrole in water. The system is based on monitoring dopant concentration, monomer concentration and pH using flow-through UV-visible spectroscopy, electrochemical detection by pulsed potential rotating disk electrode and a pH meter respectively. Control was achieved by using a closed loop PID (proportional, integral, derivative) controller for pH and a closed loop on/off controller for monomer concentration. The control of dopant concentration was found to be unnecessary when pH control was employed as the addition of p-toluenesulfonic acid to control pH compensated for dopant depletion.