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Glassy aromatic polyimides have high gas selectivity because of their high degree of packing and low mobility of molecular chains.These factors limit diffusion of small molecules through the polymer membrane.Thus,general glassy aromatic polyimides exhibit low gas permeability.The structure with loose chain packing and week inter-chain interaction make low chain packing density.Glassy aromatic polyimides having these structure show high gas permeability [1-2].To achieve high permeability,polyimide was synthesized from various diamines.These diamines show high gas permeability or selectivity with dianydride.The experimental results for the permeability and permselectivity of these polyimides were found to have tendency.The enhanced gas permeability was observed in this series of polyimides,but the permselectivity is relatively low.The chemical structure of these polyimides was determined by nuclear magnetic resonance and flourier transform infrared spectroscopy,respectively.The thermal properties were evaluated by thermal gravity analysis and differential scanning calorimetry.The density was measured by top-loading electronic valance with a density kit.The fractional free volume was calculated.Single gas permeation properties were evaluated for oxygen,nitrogen,carbon dioxide.These properties were measured by constant volume and variable pressure method.All measurements were performed at 30 ℃.The gas permeability was calculated when the permeation reaches a steady state.The gas permselectivity was calculated from the permeability ratio of two gas species [3].