Photochemical polymerization of oligothiophenes and dithienothiophene

Summary form only given. Fine fabrication of conjugated polymer materials in nanometer scale is indispensable for the novel materialization based on the quantum-size effect. From this point, photochemical polymerization is considered to be one of the promising candidates for the fine fabrication because of the recent advancement in the optical techniques. In this study, photochemical polymerization of 2,2´-bithiophene, 2,2´:5´,2-terthiophene , and dithieno[3,4-b;3´,4´-d]thiophene were investigated as an approach to the fine fabrication method for their nano-structure construction. Photochemical reactions of the thiophene derivatives were carried out in acetonitrile solution of electron acceptor such as p-dinitrobenzene or in carbon tetrachloride. All the solutions in quartz test tubes were deaerated with Ar gas bubbling before reaction. According to the steady state photoirradiation of Xe lamp, the solutions changed to black through yellow intermediates. GPC analyses of the products indicated the formation of polymers having molecular weight more than 10/sup 3/ (vs. PSt.). Absorption spectra of the polymeric products showed broad absorption in visible region peaked around 300-400 nm. From the FF-IR measurements, existence of thiophene rings of the polymeric products were confirmed. From the laser flash photolysis using XeCl excimer laser (308 nm), it was clarified that the cation radicals of monomers were formed through the electron transfer from their triplet excited states to the electron acceptor. The formation of polymers is considered by successive coupling reactions of the cation radicals.