A robust low band gap processable n-type conducting polymer based on poly(isothianaphthene)

The novel macromolecule, poly(benzo[c]thiophene-N-2-ethylhexy-4,5-dicarboxylic imide) (EHI-PITN), has been designed and synthesized. The polymer has a well-defined structure which was characterized by FTIR, H-1 NMR and C-13 NMR spectroscopies, and elemental analysis. TGA analysis indicates that the polymer has good thermal stability with an onset decomposition temperature of about 328 degreesC (N-2 atmosphere). The T-g of the polymer is about 256 degreesC. The optical properties of the conjugated polymer led to the conclusion that the band gap of EHI-PITN is ca. 1.24 eV, which is comparable with the parent PITN and its derivatives. The data are also supported by the value obtained from cyclic voltammetry. The electrochemically determined HOMO energy is 4.88 eV, and the LUMO energy is 3.59 eV. These values are comparable with those of the work functions of ITO and Mg/Ag, suggesting that EHI-PITN should find many organic electronic device applications.