NMR studies of water in polyimide films

Commercial polyimide films containing up to ～ 3 wt % water have been studied by proton, deuteron, and oxygen-17 nuclear magnetic resonance (NMR). Comparisons between NMR results and previous dielectric relaxation (DR) results for a variety of Kapton films show that there is a one-to-one correspondence between specific dielectric loss peaks and features of the ²H or ¹⁷O NMR spectra. It is concluded that water molecules, which interact only weakly with the polymer, reside in the polyimide matrix in two configurations, randomly oriented single molecules and chains of water molecules oriented perpendicular to the plane of the film. The correspondence between NMR and DR observed in water in Kapton extends to water in Upilex and to methanol and acetic acid in Kapton. © 1995 John Wiley & Sons, Inc.