Water Vapor Barrier Properties and Molecular Conformation Mechanisms of Polyimide under Mechanical Stress
The repeated stretching and folding of flexible devices during use can lead to changes in the microstructure of packaging materials,making it easier for water and oxygen from the air to enter the interior of the devices,thereby affecting their performance.Understanding the conformational changes of polymer chains in the packaging material at the microscopic level during the stretching process and the mechanism behind the weakening of water vapor barrier properties is beneficial for material design,which can help improve the performance of packaging materials and prolong the lifespan of flexible devices.Currently,conventional experimental methods face difficulties in analyzing the changes in polymer chain conformations at the microscopic level.In this study,12 types of polyimide(PI)polymer flexible packaging materials were selected.Molecular dynamics simulations were employed to investigate the attenuation of water vapor barrier properties during stretching and the relationship between Young's modulus,free volume,and PI chain conformations.This approach deepens our understanding of the mechanism behind the degradation of water vapor barrier properties during the stretching process.Furthermore,based on this understanding,the molecular conformation mechanism for improving the attenuation of water barrier properties during stretching through cross-linking methods is explored.The obtained results provide valuable references for the molecular design of polymer packaging materials.
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