Study of organic conducting polymers; synthesis, characterization and their band gap

Abstract

Eight fluorene copolymers, poly[1,3-dithienylisothianaphthene-5’,5”-diyl-alt-(9,9-dioctylfluorene-2,7-diyl)] (PFO-TINTT), poly[1,3-diselenylisothianaphthene -5’,5”-diyl-alt-(9,9-dioctylfluorene-2,7-diyl)] (PFO-SINTS), poly[1,3-bis(3’-hexylthienyl) isothianaphthene-5’,5”-diyl-alt-(9,9-dioctylfluorene-2,7-diyl)] (PFO-TINTT-Hx), poly[2,2’:5’,2-terthiophene-5’,5”-diyl-alt-(9,9-dioctylfluorene-2,7-diyl)] (PFO-TTT), poly[2,5-dithienyl-3,4-ethylenedioxythiophene-5’,5”-diyl-alt-(9,9-dioctylfluorene-2,7-diyl)] (PFO-TEDOTT), poly[(2,5-di(2-thienyl)-pyridine-5,5′-diyl)-alt-(9,9-dioctylfluorene-2,7-diyl)] (PFO-TPy25T), poly[(2,6-di(2-thienyl)-pyridine-5,5′-diyl)-alt-(9,9-dioctylfluorene-2,7-diyl)] (PFO-TPy26T), and poly[(2,5-di(2-thienyl)-thiazole-5,5′-diyl)-alt-(9,9-dioctylfluore ne-2,7-diyl)] (PFO-TThiaT) have been synthesized by Pd-catalyzed Suzuki polymerization. In these copolymers some units such as isothianaphthene (ITN), 3,4-ethylenedioxythiophene (EDOT), thiophene, pyridine, and thiazole, were present between two neighboring thiophenes, as trimeric monomers. The synthesis procedure all polymers is reported and several properties, including the energy band gap in particular, have been investigated in the first section. First, optical and electrochemical properties of the copolymers that arise from the aforementioned different connectivities were investigated in PFO-TPy25T and PFO-TPy26T. The UV-vis absorption maximum peaks of PFO-TPy25T and PFO-TPy26T in a solid state were found to be 449 nm and 398 nm respectively, with PL maximum peaks in the solid state of 573 nm and 490 nm, respectively. Using cyclic voltammetry, the energy band gaps of PFO-TPy25T and PFO-TPy26T were determined to be 3.08 eV and 3.49 eV, respectively. These results can be attributed to structrual differences, that is, kinked and linear linkage of pyridine. Second, monomers containing isothianaphthene were prepared by a ring closure reaction with Lawesson’s reagent. Strong photoluminescence ...