A new approach to hydrophobic and water-resistant poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) films using ionic liquids

Abstract

An effective strategy is presented to produce hydrophobic and water-resistant poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) films by replacing the cations associated with the sulfonate polyanion by large organic cations. Addition of specific ionic liquids (ILs) bearing large cations to the commercial PEDOT:PSS aqueous dispersion resulted in the exchange of the proton of PSS by the long hydrophobic cation of the ILs. This exchange made PEDOT:PSS hydrophobic, provoking the precipitation of the polymer in water. Recovered polymers could be dispersed in different organic solvents, preferably polar solvents such as DMF and DMSO. Electrical conductivity of the modified PEDOT:PSS films remained similar (5–8 S cm⁻¹) to that of the commercial PEDOT:PSS but the water resistance was strongly enhanced. A strong dependence of the hydrophobic behaviour of PEDOT:PSS on the nature of the counterion was observed. Thus, the water contact angle could be tuned from 48° in the case of commercial PEDOT:PSS up to 100° for the modified PEDOT:PSS.