AbstractThe interdiffusion in thin films of polyimide has been investigated using the forward recoil spectrometry (FRES) technique. Films 5–10 μm in thickness of polyamic acid spin coated onto a silicon substrate were imidized at a temperature TI. A second film, ∼300Å in thickness of perdeuterated polyamic acid was spin-coated onto the first layer and heated to a temperature TD to allow interdiffusion of the two films and imidization of the second coating. Depth profiling of the deuterated polymer by FRES showed that no interdiffusion occurred if TI>TD and TI>200°C. Substantial interdiffusion occurred if TD>TI and TI<400° C. Time averaged tracer diffusion coefficients were found to vary with the TD and TI, as well as the length of time allowed for interdiffusion. Since conversion of the deuterated polyamic acid to polyimide occurs at the diffusion temperature, the results are consistent with a relatively large diffusion coefficient for the polyamic acid (D>2.5× 10−14 cm2/sec) which decreases to a negligible value as the molecule is fully converted to the corresponding polyimide.
Unexpected Role of Electronic Coupling between Host Redox Centers in Transport Kinetics of Lithium Ions in Olivine Phosphate Materials
