Application of Polyimide Langmuir-Blodgett Films to Selective Gas Permeation

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This research project aims to prepare polyamide Langmuir-Blodgett films on porous films, and examine gas permeation behavior of the films. This is a new application of Langmuir-Blodgett films.One of the problems of this project is that the process requires treatment of acetic anhydride and pyridine, where the porous base polymer (substrate) should have resistance to this solvent system. "Juragard 240" made by polypropylene was suitable for this purpose as the base film. Polylmide Langmuir-Blodgett films were successfully prepared on this base film, which applied to gas permeation examination. It was found that increasing with the number of layers, permeation number decreased. Thus, although the permeation number was influenced by the number of layers, the permeation ratio of nitrogen and oxygen did not change remarkably with increasing the number of layers. This meant the film had a small amount of defects. So, we examined the defect in polyimide Langmuir-Blodgett films using electrochemical method. The result indicated that polyimide Langmuir-Blodgett films had much less amount of defects compared with usual fatty acid Langmuir-Blodgett films. Further more, the number of defects in polyamide Langmtiir-Blodgett films changed by charging the chemical structure of polyimides, where some polyimides offered almost defect free Langmuir-Blodgett films. Unsolved problem, the ratio of nitrogen and oxygen, should be the future problem in such thin films.