Manipulation of the ionic transport processes during redox cycling for polymer/polymer complex films of poly(styrenesulfonate)/poly(xylylviologen)

Thin films of polymer/polymer complexes of poly(styrenesulfonate) (PSS) and poly(xylylviologen) (PXV) with various ratios of the two polymers were examined using both electrochemical and electrochemical quartz crystal microbalance (EQCM) techniques. Ratios of PXV to PSS (in terms of total number of cationic to anionic charges) ranging from 1:2 to 4:1 were examined. The EQCM results clearly show that the composition of the film determines the mode of attainment of electroneutrality during redox cycling of the PXV moieties. For example, for the 1:2 film (which contains a preponderance of fixed anionic sites) charge compensation during the reduction process is accomplished predominantly, but not exclusively, by cation insertion rather than anion expulsion, and vice versa during oxidation, a predictable result based on simple charge neutrality and Donnan exclusion considerations. However, the 1:2 film does show some anion expulsion during the reduction process, and this is shown to be dependent on the time scale of the reduction process. These observations demonstrate the feasibility of rational approaches to manipulation of ionic transport processes in thin redox (or conducting) polymer films.