Hard-Cation-Soft-Anion Ionic Liquids for PEDOT:PSS Treatment.

A promising conducting polymer poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) experiences significant conductivity enhancement when treated with proper ionic liquids (ILs). Based on the hard-soft-acid-base principle, we propose a combination of a hydrophilic hard cation A (instead of the commonly used 1-ethyl-3-methyl imidazolium, EMIM) and a hydrophobic soft anion X (such as tetracyanoborate, TCB) as the best ILs for this purpose. Such ILs would decouple hydrophilic-but-insulating PSS from conducting-but-hydrophobic PEDOT most efficiently by strong interactions with hydrophilic A and hydrophobic X, respectively.