Conductivity percolation in polyiodide/polymer complexes

Variable-temperature four-probe conductivity measurements and Raman spectroscopy were investigated for iodine in poly(propylene oxide) (PPO) and NaI3 in PPO. The Raman spectra indicate the presence of both triiodide and polyiodide species in samples of I2-doped PPO. The conductivity of these PPO/I2 samples increased with increasing I2 concentration and reached a plateau at approximately 12 vol % iodine. Raman spectra at 20 °C indicate that, at concentrations less than 23 vol % I3-, the dominant species is the triiodide. Polymer salt complexes with varying amounts of I3- appear to display a conductivity threshold near Tg, at 0.2 vol fraction of triiodide