Molecular Orientation and Thermal Conductivity in Liquid Crystalline Epoxy Resins by Anionic Ring-Opening Polymerization

High thermal conductivity polymers attract significant scientific interest for their potential in various fields. However, practical applications remain limited due to their insufficient performance. Liquid crystalline epoxy resins (LCEs) exhibit high thermal conductivity due to a well-aligned molecular orientation and strong intermolecular interactions. In this study, we demonstrated BPRn as a novel LCE system for improving thermal conductivity through enhanced molecular orientation. The BPRn was designed by introducing various alkyl chains into the biphenyl moiety, and anionic ring-opening polymerization was carried out by using 2-methylimidazole as the curing agent. Thermal properties were investigated using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), thermomechanical analysis (DMA), and thermal conductivity measurements. The microstructure of BPRn was examined through polarized optical microscopy (POM) and X-ray scattering analysis. Changes in physical properties, including orientation structures with varying chain lengths, were investigated, and the potential of electronic materials was confirmed based on thermal conductivity. BPR8, with the longest alkyl spacer, showed a significantly high thermal conductivity (0.53 W/m·K). The temperature change of BPRn on a 150 °C hot plate was observed by using a thermal imaging camera to demonstrate the practical improvement in thermal conductivity.