Synthesis, characterization and evaluation of optical band gap of new semiconductor polymers with N-aryl- 2,5-diphenyl-pyrrole units

Abstract
We used chemical modification to obtain new polymers that contain pyrrole units in the main chain, with electron-withdrawing groups acting as potential organic semiconductors, by means of chemical modification of the diacetylene-containing precursors. These were prepared by oxidative coupling of terminal diacetylenes or by superelectrophilic polycondensation of diphenoxydiacetylene with isatin. Diacetylenic fragments in the precursors reacted with aromatic amines that bore electron-withdrawing substituents in the presence of copper chloride, in order to yield the corresponding diphenyl-pyrrole polymers. These were then fully characterized by NMR, IR and thermal analysis. The molecular weights of the polymers were also determined by GPC. We used UV–vis spectroscopy to derive the optical band gap of the polymers. The band gap values of synthetized polymers can be modulated by modifying the position and type of substituent. Band gaps obtained in wafer form range from 1.35 to 2.8 eV; the range required for polymer semiconductors, if they are to be employed in optoelectronic devices.