Co-deposition of conducting polymers in a room temperature ionic liquid

Abstract

This work focuses on the co-deposition of two different conducting polymers in a room temperature ionic liquid. The combination of poly(pyrrole) (PPy) and poly(3,4-ethylenedioxythiophene) (PEDOT) is investigated in 1-butyl-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (C₄mpyr TFSI). In the past, the deposition of the homopolymers from ionic liquids has proven difficult with the resultant layers exhibiting poor kinetics of both the charge and discharge reactions. Combining the two polymers as one layer, using a mixed monomer solution in an ionic liquid as the deposition media, creates a superior polymer layer. Desirable properties of the poly(pyrrole) are high specific capacitance and good mechanical properties while the desirable properties of the poly(thiophene) derivative are high electrical conductivity, good mechanical properties and high porosity. Characterisation of the co-deposited polymer layers is carried out using cyclic voltammetry, capacitance measurements, electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM) imaging. The co-deposited film is found to exhibit an improved morphology and higher ionic transport, while maintaining a similar specific capacitance to the homo-polymer PPy.