Poly(benzo[c]thiophene-2-oxide) thin film

Selective oxidation reaction of the sulfide into the sulfoxide and the sulfone with peracetic acid was applied to poly(1,3-dihydrobenzo[c]thiophene), which is a soluble precursor polymer for small-bandgap poly(benzo[c]thiophene), to give its sulfoxide and sulfone derivatives. The resulting sulfoxide and sulfone polymers were sufficiently soluble in dimethylsulfoxide or trifluoroacetic acid to prepare their thin films by casting and spin-coating methods. Mild thermal treatment of the sulfoxide polymer film around 200°C gave a new conjugated polymer, poly(benzo[c]thiophene-2-oxide) with 1.1 eV of bandgap through effective dehydrogenative conjugation. The sulfone polymer film lost most of the SO2 moiety by the thermal treatment, so that the π-conjugated path was not extended along the polymer chain.