Magnolol-Based Polybenzoxazine with Excellent High-Frequency Low-Dielectric Properties and High Thermal Stability

The rapid development of 5G/6G communication technologies requires advanced high-frequency low-dielectric materials. At the same time, these materials are required to have excellent thermal properties so that they can maintain signal integrity in harsh thermal environments. From a molecular design perspective, polybenzoxazine systems capable of simultaneously achieving excellent thermal resistance, low-dielectric constant ( k ), and low-dielectric loss ( f ) under high-frequency conditions remain limited. In this study, magnolol and p - tert -butylphenol were employed as phenolic precursors, with furfuryl diamine serving as the amine precursor for the synthesis of a new benzoxazine monomer, DFDA-MAG-PTB, designed to integrate these distinct performance attributes. Poly(DFDA-MAG-PTB) was systematically characterized, and the intrinsic role of magnolol in performance enhancement was further investigated through computational simulations. Experimental results demonstrate that the introduction of allyl functionality endows poly(DFDA-MAG-PTB) with outstanding thermal resistance (char yield at 800 °C (Y c ) = 54.1% and the temperature at 5% weight loss (T d5 ) = 378 °C) and favorable high-frequency dielectric performance ( k = 2.63 and f = 0.0064 at 10 GHz). These properties surpass those of most benzoxazine-based materials reported to date. Moreover, the use of biobased magnolol provides a renewable resource pathway, aligning with the principles of sustainable development. Overall, DFDA-MAG-PTB exhibits significant potential for applications in high-frequency, low-dielectric communication technologies.