Electrochemistry of some β‐Substituted Polythiophenes: Anodic Oxidation, Electrochromism, and Electrochemical Deactivation

Abstract

The anodic electrochemistry of two new soluble derivatives of polythiophene, namely, poly(3‐ethylmercaptothiophene) (PEMT) and poly[3, 4‐bis(ethylmercapto)thiophene] (PBEMT), is discussed in this article. For comparison with these systems, the corresponding behavior of polythiophene (PT), poly(3‐methylthiophene) (PMT), and poly(3‐hexylthiophene) (PHT) is also presented. In all five cases, the first anodic oxidation was reversible and was accompanied by reversible electrochromic behavior. When the polymers were driven to more positive potentials, there was immediate loss of electroactivity and concomitant color change to black. The threshold potential for this electrochemical deactivation varied from 1.38V (vs. SCE) for the case of PBEMT to 2.00V (vs. SCE) for PMT. The deactivation mechanism is discussed in detail for PEMT with the aid of data from voltammetry, coulometry, FTIR spectroscopy, and elemental analyses. An electrochemical cross‐linking/chain extension technique is discussed for PEMT as a means of growing smooth polymer films on electrode substrates starting from soluble oligomers in solution.