物理学报2017，Vol.66Issue(22)：257-265,9.DOI:10.7498/aps.66.227101
聚酰亚胺/功能化石墨烯复合材料力学性能及玻璃化转变温度的分子动力学模拟
Molecular dynamics simulation on the glass transition temperature and mechanical properties of polyimide/functional graphene composites
摘要
Abstract
Polyimide (PI) and the functional graphene modified with nano-composite models of hydroxyl,carboxyl and amino groups are realized by a multi-scale modeling method.The influences of the functional graphenes with different functional groups on the microstructure,mechanical and thermodynamic performances of polyimide-based composite models are investigated by the molecular dynamics simulation.The cell parameters,solubility parameters,elastic coefficients,Young's moduli,shear moduli,and the values of glass-transition temperature (Tg) of polyimide-based composite models are calculated with the COMPASS force field.Moreover,the interaction energies and hydrogen bonds of composites are analyzed to explore the internal mechanisms for improving mechanical and thermodynamic properties.The results demonstrate that the density of PI matrix is 1.312 g.cm-3 and the solubility parameter of PI matrix is 21.84 J1/2.cm-3/2,which are in accord with the actual PI parameters.The Young's moduli of the composites increase obviously with the increase of the interaction energy between the PI matrix and the functional graphenes with hydroxyl,carboxyl and amino groups at 298 K and 1 atm.The Young's moduli of PI and PI/graphene with carboxyl groups are respectively 3.174 GPa and 4.946 GPa and the shear moduli are respectively 1.139 GPa and 1.816 GPa.Comparing with pure PI/graphene composite,the average hydrogen bonds increase obviously after graphene has been functionalized.Because the interaction between the functional graphene and PI matrix increases,the movement of PI molecular chain needs more energy,and the rigidity of the composite is enhanced.The Tg of the composite also relates to the interaction energy.It is also found that the Tg of the nano-composite effectively decreases by the hybrid functional graphene.The Tg of pure PI is 663.57 K,while the Tg values of PI/graphene and PI/graphene with carboxyl groups nanocomposites are 559.30 K and 601.61 K,respectively.Moreover,the density and interaction energy of hydrogen bonds of the PGCOOH are 784.81 kcal/mol and 1.396 g/cm3,respectively,which are the largest among their counterparts of the composite systems.The elastic coefficients show that the PGCOOH is more uniform than that other composites.All of these indicate that the graphene with carboxyl group can greatly enhance the interaction between graphene and PI,improve the mechanical properties and adjust the Tg value of the PI matrix.The chemical modification of interaction energy in matrix is deemed to be of benefit to the improvement in composite performance,and the interaction energy calculation is considered to be an effective method of predicting the structures and performances of new composites.关键词
聚酰亚胺/石墨烯/分子动力学模拟/玻璃化转变温度Key words
polyimide/graphene/molecular dynamics/glass transition temperature引用本文复制引用
杨文龙,韩浚生,王宇,林家齐,何国强,孙洪国..聚酰亚胺/功能化石墨烯复合材料力学性能及玻璃化转变温度的分子动力学模拟[J].物理学报,2017,66(22):257-265,9.基金项目
Project supported by the National Natural Science Foundation of China (Grant No.61372013) and Natural Science Foundation of Heilongjiang Province,China (Grant No.E201258).国家自然基金(批准号:61372013)和黑龙江省自然科学基金(批准号:E201258)资助的课题. （Grant No.61372013）
