Electrochemical Characterisation of Polypyrrole Doped with p-Sulfonatocalix[4]arene

Polypyrrole (PPy) films doped with macrocyclic calixarene anions are attractive materials for the development of selective sensor materials and membrane systems as the incorporation of the macrocycles can confer specific recognition sites within the polymer matrix. However, unlike many other PPy films a calixarene-doped system is more complicated as calixarenes are themselves electroactive. Here we present results on the electroactivity, impedance properties and morphology of polypyrrole doped with p-sulfonatocalix[4]arene. The calixarene in the polymer was found to be irreversibly oxidised at potentials greater than 0.500 V vs. SCE and reacted to form a new redox active species that was trapped within the polymer matrix. The results from the impedance and EQCM studies indicated that the calixarene was permanently trapped within the polymer matrix and the polymer acted as a cation exchange material. In addition, the data acquired from the EQCM experiments showed that while the material displayed simple cation exchange properties at high scan rates, at lower scan rates the transport of neutral species was also observed. Overall, our findings indicate that the PPy-C4S system is suitable for use as a stable conducting polymer doped with an immobile anion within the potential window of −0.800 V to 0.500 V vs. SCE