Synthesis and characterization of thienylene–phenylene copolymers with oligo(ethylene oxide) side chains

A series of novel soluble conjugated regioregular copolymers (poly(2,5-dialkoxy-p-phenylene thienylenes)) was prepared via palladium-catalyzed Stille coupling reactions. The attachment of ethylene oxide chains to the phenylene rings ((OCH2CH2)nOR; n = 2, R = Me; n = 2, R = Bu; n = 3, R = Me) provided to the polymer increased solubility in polar solvents improved adhesion properties on glass substrates and complexing properties towards lithium ions. The structure of the polymers was established by FTIR, 1H and 13C NMR spectroscopy and elemental analysis. The physical properties were studied by X-ray diffraction, cyclic voltammetry, UV–Vis absorption and fluorescence, and Raman spectroscopy. The electrochemical properties of the copolymers compare favorably to those of the active materials used in electro-optical devices such as LED, LEC and electrochromic devices. Compared to related phenylene–thienylene copolymers the reported new materials showed lower values of the band gap and of the oxidation potential which is indicative of a highly conjugated π-system.