Development of a fully bio-based hyperbranched benzoxazine

Abstract

Fully bio-based benzoxazines are attractive thermosetting resins, but the limited variety of raw materials is a serious challenge for their further development. Herein, a new sustainable hyperbranched benzoxazine (HB), namely HB-Ra, was first designed and synthesized via the A₂ + B₃ method using resveratrol, paraformaldehyde and 5,5′-methylenedifurfurylamine (DFDA) derived from furfurylamine. The weight-average molecular weight (M_w) and polydispersity (PDI) of HB-Ra with good solubility were 17 000 Da and 2.26, respectively. Poly(HB-Ra) exhibited good thermal stability at high temperature at a 5% weight loss (T₅) of 374 °C and a glass transition temperature (T_g) of 348 °C. Remarkably, the ultralow coefficient of thermal expansion (CTE) for poly(HB-Ra) was only 8.4 ppm °C⁻¹. The low total heat release (THR) of 7.4 kJ g⁻¹ and heat release capacity (HRC) of 39.6 J g⁻¹ K⁻¹ suggest that poly(HB-Ra) can be used as a potential nonignitable material. Moreover, poly(HB-Ra) exhibited low dielectric constants (k) varying from 2.38 to 2.42 in the range of 2–18 GHz, which may meet the needs of high-frequency microelectronic devices. These good results indicate that this technically simple synthetic strategy is a nice choice to prepare other fully bio-based HBs.