TEMPERATURE-DEPENDENCE OF XE-129 NMR OF XENON IN POLYMERS

Temperature dependence of Xe-129 NMR of xenon dissolved in solid polymers is investigated in terms of the free volume model of polymers. It is shown that transitions in polymers can lead to discontinuities in the slope of the chemical shift as a function of the inverse temperature. In particular, a discontinuity in the slope of the chemical shift will develop at the glass transition and is directly related to the discontinuity in the thermal expansion coefficient of the polymer at the transition. Examples of transitions (discontinuities) observed in Xe-129 NMR are given for xenon trapped in isotactic poly(4-methyl-1-pentene) and isotactic polypropylene.