Bandgap engineering through controlled oxidation of polythiophenes

The use of Rozen's reagent (HOF×CH₃CN) to convert polythiophenes to polymers containing thiophene-1,1-dioxide (TDO) is described. The oxidation of polythiophenes can be controlled with this potent, yet orthogonal reagent under mild conditions. The oxidation of poly(3- alkylthiophenes) proceeds at room temperature in a matter of minutes, introducing up to 60 % TDO moieties in the polymer backbone. The resulting polymers have a markedly low-lying lowest unoccupied molecular orbital (LUMO), consequently exhibiting a small bandgap. This approach demonstrates that modulating the backbone electronic structure of well-defined polymers, rather than varying the monomers, is an efficient means of tuning the electronic properties of conjugated polymers. Rusted root: Rozen's reagent (HOF×CH₃CN) can convert polythiophenes to polythiophene-1,1- dioxides. The oxidation of thiophene-containing polymers, including telechelic polythiophenes, can be controlled with this potent, yet orthogonal reagent under mild conditions. By modulating the backbone of well-defined polymers, rather than varying the monomers, this approach provides an efficient means to tune their electronic properties.