Design of active ester curing agent containing imide and fluorine for plant oil-based epoxy resins with high Tg and low dielectric constant

The development of bio-based epoxy resins with high glass transition temperature ( T g ) and low dielectric constant ( D k ) is critical for replacing petroleum-derived electrical materials and addressing energy sustainability challenges. Herein, a molecularly tailored hexafunctional active ester curing agent (AE6) containing rigid imide and bulky fluorine groups is designed to cure epoxidized plant oils with various epoxy functionality. This molecular architecture endows the curing system with enhanced crosslinking capability and intrinsic low polarity, which are essential for achieving high performance. The systematic investigation of curing kinetics and structure-property relationship reveals that plant oil epoxy functionality governs cross-linked density, enabling precise control over thermo-mechanical and dielectric performance. With an increase of epoxy functionality, the resulting resin achieves superior tensile strength of 42.73 MPa, T g of 99.82 °C, and char yield of 24.67% at 600 °C, attributed to the cooperation of aromatic imide and highly cross-linked network. Additionally, the introduction of bulky fluorine group, imide structure, and abundant non-polar alkyl chains significantly reduces the polarity of the network, yielding an ultralow D k of 2.25. This work establishes a molecular engineering strategy to tailor bio-based epoxy resins for potential applications in electrical materials.