Dual-transmission line modeling of electrochemical processes in polyaniline-cellulose ester composite porous membranes.

Abstract

The charge transport processes in polyaniline (PANI) composite porous membranes have been elaborated in this study using dual-transmission line impedance model conventionally used for macroscopically homogeneous (nanoporous) membranes. Mixed cellulose ester (ME)-PANI porous membranes were prepared using various in situ chemical polymerization techniques including solution- and vapor-phase polymerizations, and two-compartment cell diaphragmatic polymerization. Each technique yielded different PANI deposition site and content in the membranes. As a result, the modeling of electrochemical impedance spectroscopy (EIS) data yielded different model parameters that have been correlated with the PANI content and deposition site (i.e., surface layering versus in-bulk deposition) in the membranes. The modeling results showed that PANI deposition enhanced charge transport by shifting the interfacial transfer mechanism at pore walls from simple double layer charging to the charge transfer involving oxidation of PANI molecular chains deposited at the pore walls of the composite membranes. In addition, in-bulk PANI deposition in the membranes by means of two-compartment cell polymerization showed several orders of magnitude faster charge transport as compared to the membranes where PANI deposited only at the surface. This study shows that pore-controlled diffusion in PANI composite porous membranes can be satisfactorily modeled using dual-transmission line model and correlated with PANI deposition site in the membranes.