基于分子动力学模拟的硅氧功能化聚酰亚胺热力学性能研究

Study on Thermodynamic Properties of Silicon Oxide Functionalized Polyimide Based on Molecular Dynamics Simulation

为从宏观和微观角度分析硅氧功能化聚酰亚胺材料的热力学性能及结构参数,以均苯型聚酰亚胺(PI)和1,3-双(3-氨基丙基)-1,1,3,3-四甲基二硅氧烷(GAPD)为研究对象,基于分子动力学(MD)建立纯PI、PI/5%GAPD、PI/10%GAPD分子模型,分析GAPD对PI微观结构及热力学性能的影响,分析GAPD含量对材料性能的影响。结果表明:GAPD能够提高PI材料的热力学性能,5%含量的GAPD改性PI的效果更显著。与纯PI相比,加入5%GAPD的PI材料的玻璃化转变温度提升了30.11 K,弹性模量提高16.1%,剪切模量提高7.25%,体积模量提高4.34%。GAPD对PI进行硅氧功能化改性改变了PI的微观结构,与纯PI相比内聚能密度提高,自由体积占比以及均方位移均略微降低。5%含量的GAPD对PI材料的微观结构影响更明显;而在材料的全原子的径向分布函数方面,利用GAPD对PI改性并没有产生较大影响。

In order to analyze the thermodynamic properties and structural parameters of silicon oxide functionalized polyimide materials from macroscopic and microscopic perspectives,benzene-homo polyimide(PI) and 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane(GAPD) were taken as the research objects,based on molecular dynamics(MD),molecular models of pure PI,PI/5%GAPD and PI/10%GAPD were established to analyze the effect of GAPD on the microstructure and thermodynamic properties of PI and the effect of GAPD content on the properties of materials.The results show that GAPD can improve the thermodynamic properties of PI materials,and the effect of 5% GAPD modified PI is more significant.Compared with pure PI,the glass transition temperature of PI material with 5% GAPD is increased by 30.11 K,the elastic modulus is increased by 16.1%,the shear modulus is increased by 7.25%,and the bulk modulus is increased by 4.34%.The silicon-oxygen functional modification of PI by GAPD changes the microstructure of PI.Compared with pure PI,the cohesive energy density increases,the free volume ratio and the mean square displacement decrease slightly.The effect of 5% GAPD content on the microstructure of PI material is more obvious.In terms of the allatom radial distribution function of the material,the use of GAPD has no significant effect on PI modification.