Si, B-containing dynamic covalent bonds enable excellent flame retardancy and reduced fire hazards for cyanate ester resin

Cyanate ester (CE) resins are distinguished by excellent dielectric properties in electronic packaging materials but face significant fire risks, with existing strategies often compromising their processability or original properties. Herein, we propose an innovative strategy involving the exchange of dynamic covalent bonds under heat stimuli aimed at forming a continuous and compact char layer to enhance the fire safety of CE resin. Using a straightforward one-pot method, dynamic Si-O and B-O bonds were integrated into a novel hyperbranched polymer (HPSiB), ensuring good compatibility with CE resin while lowering its peak curing temperature by 185 °C for facile processability. The resulting material with 6 wt% HPSiB exhibits a LOI value of 32.8% and UL-94 V0 rating, especially a low total smoke production of 6.7 m², demonstrating excellent flame retardancy and reduced fire hazards compared to reported Si or B-containing flame-retardant materials. Moreover, its glass transition temperature increased by 35 °C, along with enhanced mechanical properties and an ultra-low dielectric loss of 0.0031 at 10 GHz. These advancements highlight the significant potential of this work in developing high-performance fire-resistant materials.