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

Abstract

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/SiO 2 (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 (ε s ) and Young modulus of the PI-based composites. Due to enhanced intrinsic polarization of the SiO 2 particles and the interface polarization in the composites, the ε s 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.

Preparation and Properties of Low-Dielectric Polyimide Films Containing Tert-Butyl

“…The reason may be due to the different restrictions on the dipole moment rotation caused by the dense stacking of molecular chains and strong intermolecular interactions [30]. In addition, density functional theory (DFT) calculations [35,36] and molecular dynamics simulations (MD) [30,[37][38][39] were employed to further understand the relationship between the structure and dielectric properties of PI. A series of model PI molecules with or without a tert-butyl structure were selected.…”

“…Meanwhile, it can be found that the HOMO value of PI with a tert-butyl structure is much higher than that of PI without a tert-butyl structure, indicating that introducing a tert-butyl structure in PI is able to affect the electronic cloud distribution on the diamine and increase the energy of HOMO, thereby reducing the dielectric constant. In addition, density functional theory (DFT) calculations [35,36] and molecular dynamics simulations (MD) [30,[37][38][39] were employed to further understand the relationship between the structure and dielectric properties of PI. A series of model PI molecules with or without a tert-butyl structure were selected.…”