Processable low band gap pi-conjugated polymer, poly(isothianaphthene)

Low band gap conducting polymer poly(isothianaphthene) (PITN), which is usually considered to be insoluble and cannot be processed into film, has been prepared by dehydrogenation from its precursor polymer, poly(1,3-dihydroisothianaphthene), with sulfuryl chloride. It is found that the intermediate towards PITN is structure 2. Through propagation of structure 2, a quinoid type conjugated poly(isothianaphene) is obtained. The structure defects are benzyl chloride bonds and chlorine-doped species, which can induce aggregation of PITN in the solution. A stable PITN dispersion can be obtained by precise control of the reaction conditions together with the use of pyridine as an agent for termination of the reaction and for solvation to prevent PITN from further aggregation. The resulting PITN dispersion can be cast into film.