RELATION OF GAS-PERMEABILITY WITH STRUCTURE OF AROMATIC POLYIMIDES .1.

We examined the relation of gas permeabilities, diffusivities, and sol ubilities with the structures in various polyimide films. Permeability coefficients (P) and diffusion coefficients (D) of polyimides were me asured by the use of the high vacuum time-lag method. Glass transition s, d-spacings, and densities of polyimides were determined from the da ta with a differential scanning calorimetry, a wide angle X-ray diffra ction, and a density gradient column method, respectively. The films t ested were made from 32 kinds of polyimides, which were synthesized fr om the reactions of various diamines containing biphenyl, diphenylmeth ane, phenylether, diphenyl sulfone, or diphenyl sulfide structures wit h BPDA, 6FDA, or PMDA. The effect of ordered region in polyimide films on gas diffusivities were also examined. A number of polyimide films gave the decreased diffusivities and solubilities due to the occurrenc e of ordered region when they were annealed over glass transition temp eratures. We discussed especially diffusivities and structures of amor phous states of other polyimides except for these polyimides having or dered region. Furthermore, the relation of D having large effect on pe rmeability, with physical parameters, such as d-spacings and fractiona l free volumes (V-f), was examined in amorphous state. However, we cou ld not find good correlations between In D and d-spacing or V-f(-1). E specially, these poor correlations were observed in polyimides contain ing polar substituents. The results show that the gas diffusion of gla ssy polymers may not be interpreted only in terms of total free space or mean segment distance.