| Abstract: | Positron lifetime spectroscopy has been applied to study the temperature dependence of free-volume properties in a solvent-free polymer–salt complex polyethylene oxide (PEO) doped with ammonium iodide (NH4I, with NH ≈ 0.076) in the temperature range of 298–353 K. The observed lifetime spectra were resolved into three components and the longest lifetime, τ3, was associated with the pick-off annihilation of ortho-positronium (o-Ps) trapped by the free volume. The lifetime component, τ3, and its intensity, I3, both showed a significant variation with temperature, which followed a different course in the heating and cooling cycle. Changes in the temperature coefficient of τ3 and I3 were observed at T ≈ 328 K, the melting point of the sample. This behaviour is correlated to the temperature variation of the electrical conductivity. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 969–976, 1998 |
