Tailoring the properties in conjugated copolymer P(EDOS-co-EDOT): Electrochemical polymerization and role of heteroatom

Abstract

Considering the significant work on copolymerization, very little is known about the copolymerization of two heteroaromatic rings to generate new properties. In this work, we report a series of conducting copolymers [poly(3,4-ethylenedioxyselenophene)-co-poly(3,4-ethylenedioxythiophene)] [denoted as P(EDOS-co-EDOT)] synthesized via anodic polymerization using different feed ratios of two engaged monomers. Three feed ratios of monomers 3,4-ethylenedioxyselenophene (EDOS) and 3,4-ethylenedioxythiophene (EDOT) were used as 5:1, 1:1, and 1:5 for electrochemical copolymerization in acetonitrile containing 0.1 M tetrabutylammonium perchlorate as a supporting electrolyte. Corresponding homopolymers PEDOS and PEDOT were also prepared from monomers EDOS and EDOT, respectively, by electrochemical polymerization to sight the analogy and differences in the properties of obtained copolymers with respect to individual homopolymers. Copolymers were structurally characterized via Raman spectroscopy and X-ray fluorescence. The redox traits, optoelectronic properties and surface morphology of as-prepared polymer films were characterized using cyclic voltammetry, spectroelectrochemistry and field emission scanning electron microscope, respectively. Electrochemical stability of the copolymers was examined by repeating redox cycles. Density functional theory calculations were carried out to get an understanding of the trends in energy levels, and comparisons were made with the experimental results. Copolymer films exhibited deep blue color in the neutral state while transmissive gray in oxidized state. Electrochromic properties of the copolymers were carried out, and found highest optical contrast ratio to be 36.86% and coloration efficiency of 62.89 cm2 C − 1 for 1:5 ratio. It was found that all the copolymers have different highest occupied molecular orbital (HOMO) levels resulting from their distinct redox behavior and band gap values lie within the range of homopolymers. Thus, copolymerization is an effective route for the synthesis of polymer to tune the properties for electronic applications.