Electron Diffusion Coefficients in Hydrogels Formed of Cross-Linked Redox Polymers.

摘要

The electron diffusion coefficient (De) for the redox polymer POs-EA, an ethylamine quaternized poly(vinylpyridine) complex of Os(bipyridine)2Cl2, has been directly measured by steady-state voltammetry at interdigitated array (IDA) electrodes. In cross-linked POs-EA De decreased upon increasing the ionic strength and upon changing the hydrophilic chloride counterion to the hydrophobic perchlorate anion. In 5.0 wt% cross-linked POs-EA De is pH dependent increasing from 4.5 x 10(-9) to 1.6 x 10(-8) cm2 sec(-1) as the pyridine rings are protonated. In highly (25 wt%) cross-linked POs-EA, the motion of the chains is restricted, De is independent of pH. The results show that De increases steeply upon hydration of POs-EA. It is proposed that the extent of electron diffusion in redox hydrogel is determined by segmental motion of the polymer backbone and is therefore enhanced, rather than diminished upon swelling of the redox polymer network, that increases the static distances between redox centers.... Hydrogels, Cross-linked Redox Polymers, Poly(vinylpyridine), Os(bipyridine)2Cl2.