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Closed Access item Influence of Local Chain Dynamics on Diffusion of Gases in Polymers as Determined by Pulsed Field Gradient NMR

Authors:Garrido, Leoncio
López-González, Mar
Riande, Evaristo
Keywords:diffusion, glass transition temperature, membranes, NMR, polymer membranes, pulsed-field gradient NMR
Issue Date:2010
Publisher:John Wiley & Sons
Citation:Journal of Polymer Science Part B: Polymer Physics 48 (2) : 231–235 (2010)
Abstract:Diffusion of gases in polymers below the glass transition temperature, Tg, is strongly modulated by local chain dynamics. For this reason, an analysis of pulsed field gradient (PFG) nuclear magnetic resonance (NMR) diffusion measurements considering the viscoelastic behavior of polymers is proposed. Carbon- 13 PFG NMR measurements of [13C]O2 diffusion in polymer films at 298 K are performed. Data obtained in polymers with Tg above (polycarbonate) and below (polyethylene) the temperature set for diffusion measurements are analyzed with a stretched exponential. The results show that the distribution of diffusion coefficients in amorphous phases below Tg is wider than that above it. Moreover, from a PFG NMR perspective, full randomization of the dynamic processes in polymers below Tg requires long diffusion times, which suggests fluctuations of local chain density on a macroscopic scale may occur
Publisher version (URL):http://dx.doi.org/10.1002/polb.21892
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