Interdiffusion of PMMA and PVF sub 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) (PVF sub 2 ) above their T sub 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, the fraction of PMMA near (approx 20 A) PVF sub 2 is detected. Starting from sheets of PMMA and PVF sub 2 , which are then heated at 190 deg C for a variable time, and applying the above technique, the fractions of PMMA and PVF sub 2 that have diffused within a distance of a few A of each other can be determined. The intrinsic diffusion coefficients of PMMA and PVF sub 2 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.