Design and Characterization of Cyanate Ester Thermosets Exhibiting Both Liquid Crystalline Ordering and Vitrimer Behavior

Cyanate esters (CEs) are widely used in electronic, aerospace, and composite applications owing to their excellent thermal and mechanical properties. However, their permanent triazine networks limit reprocessability and recyclability. To overcome this limitation, liquid crystalline cyanate ester vitrimers (LCCEVs) containing mesogenic units and ester-based dynamic covalent bonds were designed and synthesized. The synthesized monomers incorporated biphenyl-based mesogens and aliphatic ester spacers, while the effects of nonylphenol catalyst content on network structure and properties were investigated. The cured LCCEVs exhibited glass transition temperatures above 150 °C and decomposition temperatures above 390 °C. LCCEV20 showed a thermal conductivity of 0.54 W m⁻¹ K⁻¹, approximately 2.1 times that of conventional bisphenol A-based cyanate esters. Furthermore, the materials demonstrated vitrimer behavior and maintained their properties after repeated reprocessing.