Correlation between morphology and NGM of 3,4-ethylenedioxythiophene (EDOT) in acetonitrile

Abstract

The nucleatlon and growth mechanism (NGM) for the electro-oxidation of 3,4-ethyienedioxythiophene (EDOT) in acetonitrile on platinum and tln(IV) oxide electrodes was determined by analyzing the potentlostatlc current-time transients inferred from electrocrystallization theory. The measurements were complemented by using atomic force microscopy (AFM) and scanning electron microscopy (SEM). Preliminary studies performed to establish the working conditions for the potentiostatic technique using cyclic voltammetry (CV) demonstrated that under the working conditions employed herein the best potential scan-rate to obtain electrodeposits of poly(EDOT) was 50 mV·s-1. The prepared polymer displayed electrochromic properties and p- and n-doping, the p-doping being chemically reversible. In addition, it was observed that the electropolymerization mechanisms on both electrode materials were a combination of two contributions: progressive nucleation, followed by diffusion-controlled tridimensional growth, PN3D dif; and instantaneous nucleation followed by three-dimensional growth under charge transfer control, IN3Dct. At shorter times, the IN3Dct contribution prevail giving rise to conical deposits, while at longer electrolysis times the polymeric deposit is made of granules, corresponding to the PN3Ddif mechanism. The electrode material has no effect at all on the global mechanism, but affects the time at which either contribution predominates. However, the morphological predictions made from the NGMs must be corroborated by other techniques before using the data to control the deposit to be prepared.