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 approximately 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 approximately 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.