High-permeability fluorinated polyimide microcapsules by vapor deposition polymerization

Spherical microcapsules (∼1 mm in diameter and ∼1 μm in wall thickness) to be used as inertial confinement fusion targets were prepared from 6FDA–ODA polyimide by vapor deposition polymerization. Compared with the previously developed PMDA–ODA polyimide microcapsules, the 6FDA–ODA microcapsules were ∼50-fold more permeable to gases including He, D2, O2, N2, Ar, and Ne, considerably more transparent in the UV–visible spectrum, and of marginally lower Youngʹs modulus, tensile strength, and elongation at break. The microcapsules possessed amorphous morphology with an amorphous d-spacing of 5.8 Å as determined by wide-angle X-ray diffraction. The cryogenic permeability of helium was measured between 133 and 295 K, and the activation energy for permeation was determined to be 12.3 kJ/mol.