NMR studies of morphology and molecular dynamics of porous polymers and diffusion of penetrants in polymer matrices

Morphology and molecular dynamics of porous polymers and the diffusion of penetrants in these polymers are studied by a variety of NMR techniques. The porous polymers under investigation are polyphenylene oxide (PXE), an amino silicone copolymer (GP6), a blend of GP6 and zinc neutralized sulfonated polystyrene (ZnSPS/GP6), the polyperfulorosulfonate ionomer Nafion, a copolymer of 2,2-bistrifluoromethyl-4,5-difluoro- 1,3-dioxole (PDD) and tetrafluoroethylene (TFE), Teflon AF 1600, and poly(1-trimethylsilyl-1-propyne) (PTMSP).; The glassy polymer PXE is studied with NMR techniques to relate the morphological characteristics to its high permeability towards small molecular penetrants. The one dimensional 129Xe spectra of PXE prepared in several ways were obtained at different temperatures. The absorbed xenon peaks around 200ppm relative to the free gas resonance indicate the dissolution of xenon in the PXE matrix. It is found that the dependence of the 129Xe chemical shift and linewidth of the absorbed xenon on temperature can be used to predict the solubility of xenon in the PXE matrix. Furthermore, the appearance of two overlapped but distinct 129Xe resonances for the absorbed xenon in PXE at low temperature reveals that there are two types of free volume regions in PXE accessible to xenon. The exchange between xenon in the two regions was detected by 129Xe 2D NOESY measurements at low temperature. The exchange rate is estimated from the NOESY patterns at various mixing times. A 129Xe NMR selective saturation technique was also used to study the diffusion of xenon in PXE. From the decay of the absorbed xenon signal, the diffusion coefficient of xenon in PXE was calculated. The high diffusion constants and the low activation energy for the xenon diffusion are consistent with the observation of high permeability towards small molecular penetrants by others.; One dimensional 129Xe studies were also conducted on the porous polymers PTMSP, Nafion and Teflon AF. The dependence of 129 Xe chemical shift and linewidth of the absorbed xenon on temperature were investigated and the results are consistent with the observation for xenon in PXE.; Diffusion of xenon in GP6 and ZnSPS/GP6 blend is measured with the 129Xe PFG NMR technique. Diffusion of xenon in the two porous polymeric materials is fast, which indicates that in the blend the diffusion of xenon is dominated by the diffusion of xenon in the GP6 component.; The diffusion of small molecular penetrants in Nafion is studied with two NMR methods. The 129Xe 2D NOESY spectra of xenon in Nafion at room temperature shows that there are two kinds of domains in Nafion and exchange between xenon in the different domains is slow. (Abstract shortened by UMI.)...