Interdiffusion of PMMA and PVF2, 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 transferred from protons to fluorines. When this magnetization is made to disappear at the fluorine sites, only those protons that are distant from fluorines greater than the distance over which cross-polarization functions will retain their magnetization. In this way we detect the fraction of PMMA near (ca. 20 angstrom) PVF2. Starting from sheets of PMMA 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 of each other. The intrinsic diffusion coefficients of PMMA and PVF2 determined from such experiments compare well with literature data. Initial attempts to fit the experimental data suggest that the concentration dependence of the diffusion coefficients cannot be neglected. (C) 1994 John Wiley & Sons, Inc.