Synthesis of new 2,5-di(thiophen-2-yl)furan-3-carbonitrile derivatives and investigation of the electrochromic properties of homopolymers and co-polymers with EDOT

Abstract

New 2,5-di(thiophen-2-yl)furan-3-carbonitriles as thiophene–furan–thiophene type monomers (2a and 2b) were synthesized by the oxidation of 2,5-di(thiophen-2-yl)-4,5-dihydrofuran-3-carbonitriles which were prepared by the reaction of 3-oxopropanenitriles with alkenes mediated with manganese(III) acetate using DDQ (2,3-dichloro-5,6-dicyano-p-benzoquinone). The monomers and their copolymers with EDOT were electrochemically polymerized in acetonitrile (AN)/LiClO₄. The electrochemical, spectroelectrochemical and morphological properties of the resulting polymer and copolymer films were investigated by cyclic voltammetry, UV-visible spectroscopy and atomic force microscopy. Observed differences in cyclic voltammetry, UV-vis spectroscopy and neutral state absorption (π–π* transition) have been accepted as evidence for the copolymerization. Copolymer films have distinct electrochromic properties according to superposition of the contained polymer properties. In addition the dissolution problem that's causing the instability of poly2b has been fixed with copolymerization. Switch time measurements showed that copolymer films are candidates for ECD applications due to their stability, fast response time and good optical contrast.