Dependence of Thermal Conductivity and Reprocessability on the Polymerization System for Liquid Crystalline Epoxy Vitrimers

The rapid advancement of compact, high-performance electrical devices increases internal heat accumulation, which harms their functionality and lifespan. One promising approach involves developing thermoset resins with intrinsically high thermal conductivity (TC), such as liquid crystalline epoxy resins (LCERs) with well-aligned mesogens, which exhibit high TC due to enhanced phonon transmittance. Still, traditional LCERs are not reprocessable, posing environmental problems. On the contrary, liquid crystalline epoxy vitrimers (LCEVs) with dynamic covalent bonds allow reprocessability via exchange reactions. Although typical vitrimers are praised for their remarkable properties, their conventional reprocessing, which involves transesterification, often necessitates the use of toxic external catalysts, causing instability in the material and promoting corrosion. Here, we demonstrate a series of catalyst-free LCEV systems based on LCEV monomers cured by cationic and anionic initiators to enhance functionality. The final products show high TC (∼0.67 W m^-1 K^-1), tripling that of traditional epoxy resin (∼0.2 W m^-1 K^-1), while also demonstrating excellent mechanical properties. Furthermore, the LCEVs display superior reprocessability using simple heating and compression, obviating the need for external catalysts. Importantly, these materials retain their properties even after several reprocessing cycles, with slight mechanical property reductions. These advancements hold promise for high-performance, eco-friendly material development for use in electrical devices.