A dual cross-linking strategy enables fully bio-based epoxy thermosets with superior low dielectric properties and mechanical properties

Bio-based epoxy resins with superior low dielectric properties and mechanical properties is of great significance for sustainable development and environmental protection. Herein, a bio-based active ester curing agent with large free volume was synthesized through a substitution reaction between magnolol and cinnamoyl chloride following by curing epoxidized linseed oil for fully bio-based epoxy thermosets. The curing kinetics of the curing behavior and the curing condition was systematic studied and optimized. The relationship between chemical structure and properties (thermo-mechanical, mechanical, dielectric, and etc.) of the resulting fully bio-based epoxy thermosets was discussed in-depth. The results showed that free radical polymerization and epoxy ringopening reactions simultaneously occurred in the curing reaction led to a dual cross-linked structure of the resulting fully bio-based epoxy thermosets. The unique structures and the introduction of the rigid benzene groups rendered the tensile strength and the thermal stability of the resulting fully bio-based epoxy thermosets high up to 33.63 MPa and 332.40 degrees C, respectively. The absence of the secondary hydroxyl groups and the presence of the low polar fatty acid chains in the backbone of the epoxy resins resulted in the dielectric constant and dielectric loss low to 3.19 and 0.012, which was much lower than those of the polymer previously reported. This study provides a simple and facile strategy for the design of environmentally friendly fully bio-based epoxy resins for microelectronics and electronic packaging application.