Constructing high‐polarization silica for polyimide‐based nanocomposites with enhanced dielectric permittivity and mechanical performances: Molecular dynamics simulations.

In this work, the silane coupling agents with 4‐carboxyphenyl (PhCOOH), amino, phenyl, 4‐aminophenyl and 4‐phenylmethylketone were employed to modify the interfaces of the polyimide/SiO2 (PIS) nanocomposites, and the effects of the interfacial structures on the dielectric and the mechanical properties for the PI‐based composites were predicted by molecular dynamics simulation. The results showed that the interface structure with PhCOOH simultaneously elevated the static dielectric permittivity (εs) and Young modulus of the PI‐based composites. Due to enhanced intrinsic polarization of the SiO2 particles and the interface polarization in the composites, the εs of PIS‐PhCOOH composites (6.66) was 28% higher than that of PIS (5.21). Young modulus of PIS‐PhCOOH (5.09 GPa) was higher than that of PIS (3.25 GPa), which was attributed to the increase of the number of hydrogen bonds and non‐bond interaction. In addition, the length of PhCOOH was found to be larger than the thickness of excluded volume region, showing that part of PhCOOH could be embedded into the gaps among PI chains and the interfacial load transfer efficiency was reinforced. These results provided an understanding of the atomic‐scale interfacial structures, which was beneficial for the design and preparation of the nanocomposites with superior dielectric and mechanical performances. [ABSTRACT FROM AUTHOR]