Abstract: The inherently low thermal conductivity and insufficient recyclability of epoxy thermosets pose substantial challenges to their sustainable development. Herein, reprogrammable, chemically degradable, and intrinsically highly thermally conductive liquid crystalline epoxy vitrimers (LCERs) were developed. These LCERs were constructed with covalent adaptable networks through introducing dual dynamic disulfide and ester bonds into the topological networks of cured liquid crystalline epoxies (LCEs). LCEs were designed to contain biphenyl mesogens connected with varied ethylene glycol oligomer spacers (-(OC₂H₄)_x-). Due to the cooperation of rigid biphenyl units and flexible -(OC₂H₄)_x-, which facilitated dense and orderly molecular packing and efficient phonon transport, LCERs achieved significantly enhanced intrinsic thermal conduction capability and mechanical performance. The resulting LCER2 (x = 2) demonstrated the highest intrinsic in-plane thermal conductivity of 1.95 W m^-1 K^-1, representing 319% that of conventional epoxy. Meanwhile, its tensile strength reached up to 27.1 MPa. Importantly, LCERs exhibited thermally reprogrammable triple-shape-memory behavior, reprocessability, and chemical degradability enabled by a covalent adaptable network containing exchangeable disulfide and ester linkages. The degraded products enabled considerably upgraded thermal conductivity and tensile strength of conventional epoxy by 90% and 158%, respectively. The results show that crystallinity is not the sole determinant of intrinsic thermal conductivity of epoxy resin. The continuity of ordered structures, molecular packing density, and chain conformation also play important roles. This study demonstrates a significant breakthrough in the bottleneck of low thermal conduction and unrecyclable characteristics of epoxies, providing a critical guidance for developing sustainable cutting-edge thermal management materials.

Key words: Epoxy vitrimers, Intrinsic thermal conduction, Thermal conduction mechanism, Liquid crystalline, Covalent adaptable network