Raman Spectroscopic Characterization of Polyselenophenes and Poly(3,4‐ethylenenedioxyselenophene)s

AbstractHerein we present novel Raman spectroscopic studies carried out for polyselenophene (PSe), poly(3,4‐ethylenedioxyselenophene) (PEDOS), and alkyl‐substituted poly(alkyl‐3,4‐ethylenedioxyselenophene) (PEDOS‐Cn: n=2, 8, and 12) homologues. These spectroscopic data are combined with morphological and structural analysis techniques, such as AFM, and DFT simulations. An investigation into the extent of π‐conjugation in PSe is presented by comparing its spectral signatures with those of a homologous series of oligoselenophenes. Our experimental data suggest that π‐conjugation in the PSe backbone extends to more than six selenophene units. The incorporation of ethylenedioxy (EDO) groups in PEDOS results in a more complex spectrum and a downshift of the CC/CC stretching vibration (or effective conjugation coordinate (ECC) mode); this provides evidence for an improvement in the π‐conjugational properties along the PSe backbone upon EDO substitution. The dispersity of π‐conjugation lengths in different PEDOS samples obtained through different synthetic routes is evaluated as a function of different structural factors. Finally, we present experimental evidence that the insertion of alkyl chains into the EDO units slightly impacts on the π‐conjugational properties of the PEDOS backbone in the non‐annealed samples (with an improved π‐electron delocalization found in PEDOS‐C8), but moderately affects the degree of molecular order of polymer films upon thermal annealing.