NMR Imaging Investigations of Case II Diffusion in Polymers

Abstract

Case II diffusion in glassy polymers is studied extensively using techniques that require destruction of the sample or interruption of the diffusion processes to make proper measurements. NMR imaging is a new technique that does not require the destruction of the sample or interruption of the diffusion processes. This investigation shows that NMR imaging is applicable to studying diffusion processes in polymers. FLASH images provide an accurate representation of the concentration profiles from diffusion of methanol into PMMA and show the major aspects of Case II diffusion. A special diffusion imaging pulse sequence provides information on the self-diffusion of the methanol in the PMMA. Images based on NMR relaxation times show the differences in molecular motions of the methanol in the bulk solvent, at the bulk-rubber interface and at the rubber-glass interface.