Synthesis and Photocyclization of Conjugated Diselenophene Pyrrole-2,5-dione Based Monomers for Optoelectronics

Imide-functionalized organic monomers and polymers are attractive in organic optoelectronic devices due to the strong electron-withdrawing ability of the carbonyl units. We report the synthesis of diselenophene-pyrrole-2,5-dione and diselenophene-phthalimide based homopolymers P1-P2 and their corresponding copolymers P3-P4. The effect of the chemical structure by having fused and nonfused diselenophene units, in the polymer backbone, on the physicochemical properties and device fabrication was investigated. The resulting homopolymers and copolymers exhibited small optical band gaps combined with the low-lying HOMO energy levels demonstrated their potential as semiconducting materials in organic field effect transistors. The morphological properties of the microstructure and packing characteristics of the polymer films were investigated by two-dimensional grazing incidence wide-angle X-ray scattering (2D GIWAXS). The diffraction patterns of the as-cast and thermally annealed polymer films illustrate that by increasing the fused aromatic cycles in the polymer backbone has an effect on the polymer film crystallinity, which was confirmed by computational studies of the dihedral angle and bond lengths of the polymers.