Visualization of Solvent Diffusion in Polymers by NMR Microscopy with Radio-Frequency Field Gradients

NMR microscopy by radio-frequency field gradients is especially well suited for studying solvent penetration in polymers, due to the weak sensitivity of the method to magnetic susceptibility variations caused by object heterogeneities and to its ability to accommodate short transverse relaxation times better than the conventional imaging procedure by static field gradients. It is shown in this paper that distinct features of the swelling process can be easily observed by this method from two-dimensional NMR images and from the diffusion profiles provided by cross-sections through that image. A specific application of the method concerns the stretched PVC for which solvent diffusion and swelling are strongly anisotropic.