Diffusion and Deuteron Nuclear Magnetic Resonance Study of the Distribution of Water Molecules in Polyimide Films

The nature and distribution of water molecules in polyimide (KAPTON) films of varying thickness is studied by diffusion and deuteron (2H) nuclear magnetic resonance spectroscopy with complementary studies of IR absorption and differential scanning calorimetry. The results supports the conclusion, drawn from a previous study, that water exists in two distinct sites called γ1 and γ2 , neither of which is strongly bound to the host polymer nor is isotropically free. The water molecules in the γ1 site are distributed uniformly throughout the volume of the film, while those in the γ2 site (which are filled only at higher values of relative humidity) appear to be in small molecular clusters.