As a new member of the high-performance organic polymer aerogel, polybenzoxazine (PBz) aerogel has the advantages of high strength, good heat resistance and flame retardancy, which is an ideal thermal insulation and ablation-resistant material. However, the influence of the structure of PBz's monomers on their properties has not been thoroughly explored, resulting in a gap between their properties and theoretical values, which largely limits their applications. Herein, in order to optimize the properties of PBz aerogels, the benzoxazine aerogels with various structures were prepared by adjusting the ratio of the oxazine rings using a simple atmospheric pressure drying method. The results showed that the chemical structure played a crucial role in the properties of aerogels, which not only determined the extent of the sol-gel reaction, but also regulated the rigidity and hydrogen bonding interactions within the polymer. Through optimization and hydrogen bonding regulation, the compressive strength of aerogels can be reached up to 76.25 MPa which was superior to current reported works. In addition, the stabilized chemical structure enabled the aerogels to have good thermal stability (peak thermal decomposition temperature of more than 500 °C) as well as low thermal conductivities of the range of 0.0560–0.0627 W/m·K. The combination of good mechanical properties, high thermal stability and low thermal conductivities offers a potential materials system for robust thermal superinsulation under extreme conditions.

中文翻译：

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通过单体结构优化，聚苯并恶嗪气凝胶具有优异的机械强度和令人满意的热稳定性

聚苯并恶嗪（PBz）气凝胶作为高性能有机聚合物气凝胶的新成员，具有强度高、耐热性和阻燃性好等优点，是一种理想的隔热、耐烧蚀材料。然而，PBz单体的结构对其性能的影响尚未得到深入探讨，导致其性能与理论值之间存在差距，很大程度上限制了其应用。为了优化PBz气凝胶的性能，采用简单的常压干燥方法，通过调节恶嗪环的比例，制备了各种结构的苯并恶嗪气凝胶。结果表明，化学结构对气凝胶的性能起着至关重要的作用，它不仅决定了溶胶-凝胶反应的程度，还调节了聚合物内部的刚性和氢键相互作用。通过优化和氢键调节，气凝胶的抗压强度可以达到76.25 MPa，优于现有报道的工作。此外，稳定的化学结构使气凝胶具有良好的热稳定性（峰值热分解温度超过500℃）以及0.0560-0.0627 W/m·K范围内的低导热系数。良好的机械性能、高热稳定性和低导热系数的结合提供了一种潜在的材料系统，可在极端条件下实现稳健的超隔热。