Synthesis and optical and electrochemical properties of novel polyethers containing isolated distyrylbenzene derivatives and side-aromatic 1,3,4-oxadiazole chromophores

New polyethers (P2, P4) with isolated emitting distyrylbenzene derivatives and pendant aromatic 1,3,4-oxadiazole chromophores have been prepared by the Horner-Wadsworth-Emmons olefination reaction. Polyethers P1 and P3 without oxadiazole groups have also been synthesized for comparison. The reduced viscosities were about 0.20-0.33 dL/g, and the solubility in organic solvents increased with a number of side methoxy or ethoxy substituents in the distyrylbenzene section. Absorption spectra showed two peaks at 371-388 and 304 nm that corresponded to the π-π* transition of the conjugated distyrylbenzene derivatives and aromatic oxadiazoles, respectively. The band gaps were at 2.76-2.85 eV, which were calculated from onset absorption in the film state. The photoluminescence (PL) maxima were at 459-469 nm, indicating that they are blue-emitting materials, and the relative PL quantum efficiencies were 0.62-0.77 and 0.23-0.40 in solution and the film state, respectively. Cyclic voltammetric investigations demonstrated that oxadiazole moieties decrease the barrier of electron injection but also retard hole injection.