Ultrastiff Biobased Epoxy Resin with High T g and Low Permittivity: From Synthesis to Properties

Harvesting biobased epoxy resins with improved thermomechanical properties (e.g., glass transition temperature T g and storage modulus), mechanical and dielectric similar and even superior to that of bisphenol A epoxy resin (DGEBA) is vital to many applications, yet remains a substantial challenge. Here we develop a novel eugenol-based epoxy monomer (TEU-EP) with a branched topology and a very rich biobased retention (80 wt %). TEU-EP can be well cured by 3,3′-diaminodiphenyl sulfone (33DDS) and the resultant TEU-EP/33DDS system can be considered as a “single” epoxy component, exhibiting adequate reactivity at high processing temperatures. Importantly, compared with DGEBA/33DDS, TEU-EP/33DDS achieves a 33 °C, 39% and 55% increment in the glass transition temperature, Young’s modulus, and hardness, respectively, and shows the improved creep resistance and dimensional stability. TEU-EP/33DDS is also characterized by the considerably reduced permittivity, dielectric loss factor, and flammability with high yield of pyrolytic residual. Overall, TEU-EP endows the cured epoxy with a number of the distinguished properties outperforming its DGEBA counterpart, and therefore may find practical applications in demanding and even cutting-edge areas.