Molecular dynamics simulation of polymer wrapping for interfacial characteristics of aligned carbon nanotube/polyimide nanocomposites

Abstract

AbstractThe interaction properties can be significantly improved by using conjugated polymers with aromatic rings for carbon nanotube (CNT)‐reinforced composites. In this study, we investigated the influence of the molecular structure of the polyimide (PI) conjugated polymer on the mechanical properties and interfacial characteristics of CNT/PI composites. To that end, nanocomposites composed of aligned multi‐walled carbon nanotubes (MWNTs) and PI with three different molecular structures were examined. Tensile tests, small‐angle x‐ray scattering (SAXS), and molecular dynamics (MD) simulations were conducted, which revealed significant variations in the tensile properties among the three aligned MWNT/PI nanocomposites. The SAXS analyses indicated that MWNT/BPDA‐PDA had the largest interfacial specific surface area, as corroborated by the MD simulation results, which further demonstrated that the rigidity of the molecular structure influenced the extent of wrapping the PI chains around MWNTs. A highly rigid molecular chain hindered the intrachain folding of the PI chain, facilitating better wrapping of the MWNTs and a larger interfacial area. The MWNTs induced conformational changes in the PI chain owing to π–π stacking. Hermans orientation factor revealed that BPDA‐PDA exhibited the highest degree of orientation with MWNTs, whereas BTDA‐MPD displayed the greatest extent of MWNT‐induced conformational changes. The calculated interaction energy confirmed that MWNT/BTDA‐MPD exhibited the strongest interface strength (−41.50 Kcal/mol/nm2), which was 36.32% and 43.03% higher than that of MWNT/BPDA‐ODA and MWNT/BPDA‐PDA, demonstrating its superior tensile properties. This study provides insights into the interfacial characteristics between conjugated polymers and CNTs, which are essential for designing interfaces and developing high‐performance nanocomposites.Highlights Interfacial interaction between polyimide and aligned carbon nanotubes was investigated. Modulation by polyimide structures on the mechanical property of composite was revealed. The rigidity of the polyimide hinders the folding and facilitates the wrapping. The interfacial interaction induces molecular orientation in polyimide can be observed by molecular dynamic simulation.