Preliminary study on alternating thienylene/phenylene copolymers functionalized with an electron-donating or -withdrawing group

Three novel regioregular polymers substituted with electron-donating or -withdrawing groups, poly[1,4-bis(3-X-2,5-thienylene)phenylene-alt-2,5-dioctyl-1,4-phenylene] [PBT(X), X = OMe, H, CN], were synthesized and characterized. They are highly fluorescent, but the absorption wavelength of PBT(CN) and PBT(OMe) are shifted toward the blue and red regions, respectively, with reference to PBT(H). The onset reduction potential of PBT(CN) is –1.11 V versus SCE (saturated calomel electrode), which is higher than that of the cyano derivative of poly(phenylene vinylene), indicating it be a good candidate as electron transport layer. The onset oxidation and reduction potentials of PBT(OMe) (0.96 and –1.28 V versus SCE respectively) suggest it would perform well as emissive layer in light-emitting display applications.