Influence of the Electropolymerization Parameters on the Doping Level of Polybithiophene Films Grown in Acetonitrile and Water

Electropolymerized polythiophene (PTh) is a conductive polymer with low crystallinity, excellent thermal stability, and good conductivity. Its applications strongly depend on the electrochemical conditions employed during film growth, the nature of the doping counterion, the substituents attached to the thiophene ring, and the reaction medium employed. Electropolymerization of bithiophene (BTh) to produce polybithiophene (PBTh) can be successful both in aqueous and organic media. The objective of the present study was to compare the influence of the electropolymerization conditions on the doping level (δ) of PBTh films. A high doping level was reached using ACN as solvent (% δ = 25.58% ± 0.77), while in water the electropolymerization was strongly inhibited. The study of in-situ conductance during electropolymerization in ACN showed a conductance increase with the number of cycles, while conductance did not increase in water. This electropolymerization inhibition is attributed to a nucleophilic attack by the H2O molecule on the cationic species formed during the oxidation of PBTh.