AbstractRedox‐active poly(xylyl viologen) (PXV) was cast on a glassy carbon electrode and soaked into poly(ethylene oxide) (PEO) oligomers containing different supporting electrolytes. The obtained peak current was the function of the anion radius of the supporting electrolytes in PEO No cation dependence was observed. Anions migrated in the PXV matrix during the redox reaction and smaller anions gave a larger peak current, reflecting faster migration in the PXV matrix. However, when PXV was mixed with poly(styrene sulfonate) (PSS) on the carbon electrode to form a PXV–PSS complex, a similar voltammetric study revealed that only cations migrated in the PXV–PSS matrix during the redox reaction. Smaller cations gave larger peak currents for the PXV–PSS complex‐coated electrode in PEO oligomers. The ion radius dependence of the peak current in the PXV–PSS complex was smaller than that in the PXV system. This suggested that the PXV–PSS complex domain was polar but considerably smaller in the