On free volume of polymers above the glass transition



The magnitude of the activation energy for diffusion, ED is shown to be inversely dependent on the fractional free volume of the polymer above Tg. From the proportionality of ED above and below Tg, the magnitude of ED below Tg is also inversely dependent on the free volume in that temperature range. While this correlation holds very well for our determinations of fractional free volume above Tg it does not correlate with the Simha-Boyer fractional free volume below Tg, contrary to expectations.