Scattering Studies on Poly(3,4-ethylenedioxythiophene)–Polystyrenesulfonate in the Presence of Ionic Liquids

The demand for lower cost and flexible electronics has driven industry to develop alternative transparent electrode (TE) materials to replace indium tin oxide (ITO). ITO is the benchmark TE on the market, but its high cost and low flexibility limit it for use in future technologies. Recent work has shown the combination of the conducting polymer poly(3,4-ethylenedioxythiophene)–polystyrenesulfonate (PEDOT:PSS) with the ionic liquid 1-ethyl-3-methylimidazolium tetracyanoborate (EMIM:TCB) is a viable ITO replacement. The work presented here investigates the nature of the interaction between PEDOT:PSS and EMIM:TCB in the solution state. A combination of scattering methods is used to illustrate a novel, multilength scale model of this system. At length scales larger than 300 nm PEODT:PSS adopts a microgel-like structure, and below ∼300 nm the system adopts an entangled polyelectrolyte mesh structure. As EMIM:TCB is added, the microgel interior adopts a more neutral polymer mesh structure as EMIM:TCB concentra...