Vanillin-Derived Degradable and Reprocessable Liquid-Crystalline Epoxy Resins with High Intrinsic Thermal Conductivity.

The demand for high-functionality and miniaturized consumer electronics is driving the development of polymer packaging materials with intrinsically high thermal conductivity. Herein, a novel vanillin-based liquid-crystalline epoxy monomer (BEP) and three curing agents (ICA-1, ICA-2, and ICA-3) containing conjugated aromatic imine structures were synthesized. The results of X-ray diffraction measurements show that the structural order of the epoxy resins based on BEP and ICAs increases with the number of conjugated benzene rings in ICAs. Compared with the conventional epoxy reference (0.23 W m-1 K-1), the prepared liquid-crystalline epoxy resins exhibit enhanced intrinsic thermal conductivity (0.28-0.38 W m-1 K-1) due to the synergistic effect from the liquid-crystalline phase structure in BEP and the additional ordered structure (via π-π stacking) in ICAs. Both experimental and molecular dynamics calculation results show that the thermal conductivity of the epoxy resins is proportional to the length of the conjugated structures in ICAs. Owing to the incorporation of dynamic aromatic imine bonds, the three cured epoxy resins based on BEP and ICAs demonstrate excellent reprocessibility through imine metathesis and are chemically degradable in the amine solution.