INTERDIFFUSION OF PMMA AND PVF(2) STUDIED BY SOLID-STATE NMR

A previously published new solid-state nuclear magnetic resonance (NMR ) method is applied to the interdiffusion of poly (methyl methacrylate ) (PMMA) and poly (vinylidene fluoride) (PVF2) above their T(g). Via a variation of the cross-polarization technique magnetization is transf erred from protons to fluorines. When this magnetization is made to di sappear at the fluorine sites, only those protons that are distant fro m fluorines greater than the distance over which cross-polarization fu nctions will retain their magnetization. In this way we detect the fra ction of PMMA near (ca. 20 angstrom) PVF2. Starting from sheets of PMM A and PVF2, which are then heated at 190-degrees-C for a variable time , and applying the above technique, we can determine the fractions of PMMA and PVF2 that have diffused within a distance of a few angstrom o f each other. The intrinsic diffusion coefficients of PMMA and PVF2 de termined from such experiments compare well with literature data. Init ial attempts to fit the experimental data suggest that the concentrati on dependence of the diffusion coefficients cannot be neglected. (C) 1 994 John Wiley & Sons, Inc.