Synthesis, solid-state, and charge-transport properties of conjugated polythiophene-S,S-dioxides

An alkylated semiconducting polymer comprising alternating bithiophene-[all]-S,S-dioxide and aromatic monothiophene units in the polymer backbone was synthesized with the intent of modifying the energy gap and lowest unoccupied molecular orbital for use as a stable n-type semiconductor. Films spun from this semiconducting polymer were characterized utilizing X-ray scattering, near edge X-ray absorption fine structure spectroscopy, ultraviolet photoelectron spectroscopy, and thin-film field effect transistors to determine how oxidation of the thiophene ring systems impacts the structural and electronic properties of the polymer. The thiophene-S,S-dioxide polymers have lower optical and electrical band gaps than corresponding thiophene polymers. X-ray scattering results indicate that the polymers are well ordered with the pp stacking distances increased by 0.4 angstrom relative to analogous thiophene polymers. The electrical stability of these polymers is poor in transistors with a drop in the field effect mobility by approximately one order of magnitude upon addition of just 5% of the thiophene-S,S-dioxide unit in a copolymer with thiophene. (C) 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013