Coupling Agent-Induced Fabrication of Nanoporous Polybenzoxazine Aerogels with Balanced Thermal Insulation and Compressive Performance for Thermal Insulation Applications

The preparation of nanoporous polybenzoxazine aerogels with environmentally benign solvents has drawn increasing interest in recent years, but the strategies for enhancing their mechanical strength and the mechanisms by which microstructural evolution influences skeleton strength are not clear yet. Silicon functionalization, particularly using silane coupling agents, provides a practical route to tailor the microstructure and improve the mechanical properties of organic aerogels while retaining their thermal insulation. Drawing inspiration from this mechanism, we herein propose the rational design of a multifunctional boron-doped polybenzoxazine aerogel modified by methyltrimethoxysilane and 3-glycidoxypropyldimethoxymethylsilane (BPBz/MK hybrid aerogel) with a special nanostructure evolution and high mechanical strength through an eco-friendly solvothermal method based on ethanol-soluble benzoxazine (Bz) monomer. The BPBz/MK hybrid aerogel exhibits a remarkable integration of properties, including exceptional thermal insulation (0.0325 W m–1·K–1), outstanding fire retardant properties, and intrinsic hydrophobicity with a water contact angle of 145°. The mechanical strength of BPBz/MK hybrid aerogels was substantially improved, with modulus increasing from 0.11 to 4.22 MPa, an enhancement by a factor of approximately 38.36. Collectively, these characteristics position the material as an excellent thermal insulation candidate across a broad range of uses in demanding environments.