Abstract
The diffusion coefficient ( D PV 2+ ) and the concentration ( C a PV 2+ ) of the actually electroactive PV 2+ in the poly(ethylene oxide) (PEO, average molecular weight: 400) media containing 0.1 M LiClO 4 and various concentrations of propyl viologen dibromide (PVBr 2) could be separately estimated without previous knowledge of either, based on a combined use of steady-state cyclic voltammetry at carbon fiber electrodes (diameter: 9 μm) and potential-step chronoamperometry at glassy carbon electrodes (diameter: 1 mm) as a function of PVBr 2 concentration ( C PV 2+ = 2–20 mM) and temperature (10–60°C). Both C a PV 2+ and D PV 2+ significantly varied with C PV 2+ C a PV 2+ values were smaller than C PV 2+ , indicating that all of the dissolved PVBr 2 are not actually electroactive. D PV 2+ decreased with increasing C PV 2+ (and C a PV 2+ ), and the charge transport in the PEO matrix was thus found to occur not via the electron-hopping process between PV 2+ and PV + (the monocation state of PV 2+), but via the physical diffusion of PV 2+. Further, it became apparent that at C PV 2+ > 5 mM the temperature dependence of D PV 2+ is not the Arrhenius type and follows the VTF equation, that is, PV 2+ ions are transported along with the segmental motion of the PEO chains. Based on the DSC measurements of the PEOLiClO 4 (0.1 M)PVBr 2 complexes, their glass transition temperatures were found to decrease with increasing C PV 2+ , suggesting that PVBr 2 functions as a plasticizer.
Published Version
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