Poly(1,4-bis[2-(4-hexylthiophene)]-2,5-dimethylphenylene): a new conjugated electroluminescent polymer

We report the synthesis of the conjugated polymer, poly(1,4-bis[2-(4-hexylthiophene)]-2,5-dimethylphenylene), by FeCl3 oxidation in high yield. The polymer has perfect head-to-head (HH) linkages between the thiophene rings, exhibits good solubility in conventional organic solvents, and exhibits high thermal stability. The optical band gap is ∼2.76 eV. The polymer emits greenish-blue light under UV irradiation with the emission maximum at 507 nm; the photoluminescence (PL) efficiency (solid thin film) is ∼10%. The external electroluminescence efficiency was measured to be 0.0012% for single layer devices using Al as the cathode material and 0.0035% for single layer devices using Ca as the cathode material.