Synergistic Enhancement of Mechanical, Thermal, and Dielectric Properties in Bio-Based Daidzein Epoxy Resins via Ladder-like and Hyperbranched Polysiloxane

As the electronic device industry advances toward higher frequencies, faster speeds, and greater integration, packaging materials face increasingly stringent demands for dielectric performance and thermal stability. Traditional petroleum-based epoxy resins struggle to meet the sustainability requirements of future generations of electronic packaging due to their high dielectric constant, reliance on nonrenewable resources, and the potential toxicity of BPA. This study successfully prepared a biobased epoxy resin with a low dielectric constant, CH-DEPC, by designing and synthesizing ladder-like polysiloxane (CEOS) and hyperbranched polysiloxane (HBPSi), and incorporating them into diglycidyl ether of daidzein (DEP). Experimental results demonstrate that the synergistic interaction between CEOS and HBPSi precisely regulates the chain stiffness and cross-link density of the cured polymerization network. Among these, 3C5H-DEPC demonstrated outstanding comprehensive performance: its film tensile strength reached 57.47 MPa, with fracture toughness at 3.18 MJ/m3, representing increases of 101.7% and 297.5% over DEPC, respectively. The cured network cross-link density significantly improved by 438.1%, achieving a char yield as high as 48.68% at 800 °C. Furthermore, the LOI value is as high as 30.7%, and the quality loss after 5 days of thermal aging at 180 °C is only 0.22% (R180–5 = 99.78%). The dielectric constant (Dk) and dielectric loss (Df) of the film at 1 MHz decreased to 3.189 and 0.041, respectively, representing reductions of 45.6% and 29.3% compared to DEPC. The surface water contact angle reached 128.87°, and water absorption decreased by 60%. This study offers a design strategy for green, sustainable, high-performance low-dielectric materials and enhances understanding of multitopology polysiloxane synergy in epoxy resins, providing a theoretical foundation for biobased polymer applications in high-end electronic packaging.