Rheological and Mechanical Properties of Thermoplastic Crystallizable Polyimide-Based Nanocomposites Filled with Carbon Nanotubes: Computer Simulations and Experiments

Recently, a strong structural ordering of thermoplastic semi-crystalline polyimides near single-walled carbon nanotubes (SWCNTs) was found that can enhance their mechanical properties. In this study, a comparative analysis of the results of microsecond-scale all-atom computer simulations and experimental measurements of thermoplastic semi-crystalline polyimide R-BAPB synthesized on the basis of dianhydride R (1,3-bis-(3 ',4-dicarboxyphenoxy) benzene) and diamine BAPB (4,4 '-bis-(4 ''-aminophenoxy) biphenyl) near the SWCNTs on the rheological properties of nanocomposites was performed. We observe the viscosity increase in the SWCNT-filled R-BAPB in the melt state both in computer simulations and experiments. For the first time, it is proven by computer simulation that this viscosity change is related to the structural ordering of the R-BAPB in the vicinity of SWCNT but not to the formation of interchain linkage. Additionally, strong anisotropy of the rheological properties of the R-BAPB near the SWCNT surface was detected due to the polyimide chain orientation. The increase in the viscosity of the polymer in the viscous-flow state and an increase in the values of the mechanical characteristics (Young's modulus and yield peak) of the SWCNT-R-BAPB nanocomposites in the glassy state are stronger in the directions along the ordering of polymer chains close to the carbon nanofiller surface. Thus, the new experimental data obtained on the R-BAPB-based nanocomposites filled with SWCNT, being extensively compared with simulation results, confirm the idea of the influence of macromolecular ordering near the carbon nanotube on the mechanical characteristics of the composite material.

Automated summary

It has been found that the mechanical properties of thermoplastic semi-crystalline polyimides can be enhanced by a strong structural ordering near single-walled carbon nanotubes (SWCNTs). In this study, a comparative analysis of computer simulations and experimental measurements was performed to investigate the rheological properties of nanocomposites based on thermoplastic semi-crystalline polyimide R-BAPB synthesized with SWCNTs. The results show that the viscosity of SWCNT-filled R-BAPB increases in the melt state due to the structural ordering near SWCNTs. Additionally, the orientation of polyimide chains near the SWCNT surface leads to anisotropic rheological properties and improved mechanical characteristics of the nanocomposites in the glassy state.