Characterization of superabsorbing polymers by NMR imaging

 The use of NMR imaging techniques for the characterization of superabsorbing polymers is explored. Spatial differences in the cross-link densities of polyacrylate-based superabsorbing particles are investigated by parameter-selective ¹H NMR imaging of samples swollen with water. Images of the transverse relaxation time and of the self-diffusion coefficient of the absorbed water provide valuable information on the local water mobility and, thus, indirectly also on the polymer. The time evolution of the swelling process was also studied by NMR images acquired after different swelling times. Moreover, using magic-angle-spinning imaging, the influence of mechanical load on the swollen particle was investigated by taking advantage of the centrifugal forces on the spinning sample. These experiments indicate the presence of two water components, one strongly adsorbed, while the other is relatively mobile. Received: 2 November 1999 Accepted: 17 December 1999