MULTIPLE REDOX POLYMERS PREPARED BY COVALENT AND ELECTROSTATIC BINDING TO POLY(VINYLPYRIDINE-CO-STYRENE) - COOPERATIVE BINDING AND POTENTIAL-INDUCED ELECTROSTATIC BINDING

Binding of [Ru-III(edta)(OH2)](-) (edta=ethylenediaminetetraacetate) t o pyridine (py) sites in poly(vinylpyridine-co-styrene) (PVPS; 10% sty rene) is induced by exposing a PVPS-coated glassy carbon (GC) electrod e to dilute solutions of [Ru-III(edta)(OH2)](-). This polymer is capab le of incorporating [Mo-IV(CN)(8)](4-) and the amount of anion incorpo rated is augmented by holding the electrode in the Ru-II state in line with expectations due to charge balance. Rotating-disc electrode expe riments confirm that the current observed due to the MV(2+) (MV(2+)=1, 1'-dimethyl-4,4'-bipyridinium) ion arises from membrane diffusion thro ugh the polymer rather than from pinhole effects. Similarly, [Ru-II(NH 3)(5)(OH2)](2+) was covalently bound to PVPS to give a polymer which c an bind [Mo-IV(CN)(8)](4-) by ion-exchange, the amount depending on th e Ru oxidation state. Go-operative binding of both [Ru-III(edta)(OH2)] (-) and [Ru-II(NH3)(5)(OH2)](2+) to PVPS results in a single broad wav e composed of the two overlapping Ru-III/II redox couples present in a 2:1 ratio consistent with their respective charges. The {[Ru-III(edta )(OH2)(py)](2)[Ru-II(NH3)(5)(py)]} polymer can incorporate redox-activ e ions from either MV(2+) or [Mo-IV(CN)(8)](4-) containing solutions, but at lower levels than observed for the pure [Ru-III(edta)(py)](-) a nd [Ru-II(NH3)(5)(py)](2+) polymers. The diffusion coefficient for cha rge transfer, D-ct, is higher for the mixed polymer, reflecting its gr eater concentration of redox sites. The mixed polymer is capable of bi nding both MV(2+) and [Mo-IV(CN)(8)](4-) species, yielding a redox pol ymer which can be switched into six different redox states.