Relationship between thermal properties and diffusion coefficients of gases for polyimide films

The relationships between the chemical structure, packing density (1/V_F), and cohesive energy density (CED) and the thermal properties of polyimides were investigated. Particularly, the correlation of tan δ measured by stress–strain/thermal mechanical analysis with 1/V_F and CED was found for eight polyimides. We measured the relationship between the apparent diffusion coefficient (D_a) and 1/V_F and CED, respectively, as described in previous articles. From these experiments, we found that the thermal properties, especially tan δ, were correlated with the apparent diffusion coefficient of gas. These results are well explained by use of micro-Brownian motion. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 389–397, 1997