Synthesis and properties of azomethine-containing bis-mesogenic liquid-crystalline epoxy resins
摘要
A liquid-crystalline epoxy monomer (ABAP-EP-Si) bearing azomethine-based bis-mesogenic units was synthesized and cured with p-aminobenzenesulfonamide to form cross-linked networks with tunable structural order. The chemical structure and mesomorphic behavior of ABAP-EP-Si were confirmed by FT-IR, 1H NMR, XRD, DSC, and polarized optical microscopy. The monomer exhibits a broad enantiotropic liquid-crystalline phase window between 59 and 121 °C, substantially wider than that of its monomesogenic analogue. The retention of liquid-crystalline domains in the cured networks is strongly dependent on the curing temperature, and the preserved ordered domains contribute to enhanced thermal conductivity and fracture toughness compared with networks cured at higher temperatures. The sample cured at 120 °C exhibits the highest crystallinity, a fracture toughness of 1.68 kJ m−2, and a thermal conductivity of 0.3142 W m−1 K−1, approximately 1.57 times that of conventional epoxy resins (~ 0.2 W m−1 K−1), while exhibiting a high char yield of 41.55% at 600 °C. Furthermore, a lap shear strength of 4.60 MPa on aluminum alloy indicates favorable interfacial adhesion for metal bonding. These results demonstrate that integrating azomethine bis-mesogens with flexible siloxane spacers is an effective strategy to broaden the liquid-crystalline window and enhance the intrinsic thermal conductivity of epoxy thermosets while maintaining balanced mechanical performance.