Preparations and Electrochemical Characterizations of Conductive Porphyrin Polymers

Abstract

5,10,15,20-Tetrakis(4-aminophenyl)porphyrin (TAPP) undergoes oxidative polymerization to form electronically conductive, nanofibrous structures in which the porphyrin units are linked by phenazine bridges. Polymerizations by chemical oxidation, electrochemical oxidation, and interfacial oxidative polymerization are described. Poly-TAPP (pTAPP) films have been characterized using scanning electron microscopy, cyclic voltammetry, electrochemical impedance spectroscopy, and UV–vis spectroscopy. The polymer morphology is consistently nanofibrous, with some differences depending on the specific synthetic method. The polymer films show distinctive electrochromism at different redox and protonation states. A Pourbaix diagram correlates the proposed redox and protonation states of the polymer with applied potential, pH, and perceived color of the film. pTAPP shows the lowest resistance to oxidative doping/dedoping at low pH and potentials between +0.4 and +0.5 V vs Ag/AgCl.