Solid state polymerization of 3,4-dioxythiophene derivatives

Abstract

New 3,4-dialkoxythiophene derivatives were synthesized based on structural modification of 3,4-ethylenedioxythiophene (EDOT). Five derivatives of diethyl 3,4-dialkoxythiophene-2,5-dicarboxylate were prepared from dihydroxy precursor in 9.4-61.1% yields. Only the vinyl-3,4-ethylene derivative could be hydrolyzed to the corresponding dicarboxylic acid in 92.5% yield. Decarboxylation provided the thiophene monomer in 59.5% yield. Halogenation of thiophene monomer with N-bromosuccinimde (NBS) and pyridinium tribromide provided dibromothiophene and tetrabromothiophene derivative in 96.0% and 23.7% yields, respectively. Oxidative polymerization of thiophene monomer and thermal polymerization of dibromothiophene supposedly gave the structurally similar polymer in 72.2% and 68.4% yields, respectively. The tetrabromoothiophene could be thermally polymerized in solid state to obtain polymer in 45.4% yield. Characterization of these resulting insoluble polymers were performed by UV-Vis and IR spectroscopy.