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分子动力学模拟是研究分子结构与性能的一种十分重要且有效的方法。为研究聚酰亚胺(PI)分子的微观降解机理,利用分子动力学软件,采用基于密度泛函理论(DFT)的量子力学程序对聚合度为5的均苯型聚酰亚胺分子进行了降解模拟。通过对Mulliken重叠布居数及PI分子降解过程的计算与模拟,发现PI分子主链结构上的醚键(C—O—C)、酰亚胺环(C—N—C)上的C—N键较弱,在PI分子受热过程中容易断裂,造成PI分子聚合度降低;醚键断裂和酰亚胺环开环可能导致PI分子有2种不同的降解路径,其最终降解产物主要有H2O、NO、CO、CO2及NO2等气体。该研究成果有助于在原子水平对PI的结构与性能进行研究,从而更深入认识PI分子热降解的微观机理。
Molecular dynamics simulation is a very important and effective method to study molecular structure and properties. In order to study the mechanism of microscopic degradation of polyimide (PI) molecules, molecular dynamics software and the quantum mechanics program based on density functional theory (DFT) Degradation simulation. Through the calculation and simulation of Mulliken overlap population and PI degradation process, it was found that the ether bond (C-O-C) on the main chain of PI molecule and the C-O- N bond is weak, PI molecule is easily broken during heating, resulting in the decrease of PI degree of polymerization; ether bond cleavage and imide ring opening may lead to two different degradation pathways of PI molecule, and the final degradation products of the PI molecule are mainly H2O , NO, CO, CO2 and NO2 and other gases. The results of this study contribute to the study of the structure and properties of PI at the atomic level to further understand the micro-mechanism of thermal degradation of PI molecules.