Aligned Structure of Mesogenic Motifs in Epoxy Resin and Their Thermal Conductivities
The epoxy-based crosslinked polymer with the mesogenic group has been studied as a candidate resin material with high thermal conductivity due to the ordered structure of the mesogenic groups. In this study, we conducted all atomic molecular dynamics simulations with iterative crosslinking procedures on various epoxy resins with mesogenic motifs to investigate the effect of molecular alignment on thermal conductivity. The stacked structure of aromatic groups in the crosslinked polymer was analyzed based on the angle-dependent radial distribution function (ARDF), which was categorized into three groups depending on their monomer shapes. The thermal conductivities of resins were higher than conventional polymers due to the alignment of aromatic groups but no distinct correlation with ARDF was found. Therefore, we conducted a further study about two structural factors that affect the alignment and the TC by comparing the resins within the same groups: the monomer with alkyl spacer, and functional groups in hardeners. The alkyl chains introduced in the epoxy monomers induced more stable stacking of aromatic groups but thermal conductivity was lowered as they inhibit the phonon transfer in the microscopic scale. In the other case, the functional groups in the hardener lowered the TC when the polar interaction with other polar groups in the monomer is strong enough to compete with the pi-pi interaction. These results represent how the various chemical motifs in mesogenic groups affect their alignment in the atomistic scale, and also how they have effects on the TC consequently.
- Nanoscale Adv., 2022, 4, 1970-1978