Radiotracer self‐diffusion measurements in poly(ethylene oxide) and poly(propylene oxide) electrolytes

Radiotracer measurements of the 22Na+ and S14CN− diffusion coefficients in PEO‐NaSCN (x = 6, 8 and 12) and PPO‐NaSCN (x = 8) are reported, where PEO = poly(ethylene oxide), PPO = poly(propylene oxide), and x = [EO units]/[NaSCN] or [PO units]/[NaSCN]. The results are compared with ionic conductivity measurements on the same samples. Measurements for the PEO samples were taken above the melting point of pure PEO and the results interpreted, particularly for the sample most dilute in salt, in terms of ‘free ions’ as the dominant charge carriers. For PPO the results are less clear, although there is good evidence for the onset of ion aggregation prior to separation of salt at higher temperatures.