Liu Rui, Zhang Yifeng, Liu Wenyan, Yu Zhiyu, Yu Ruizhi, Yan Hongxia
Shaanxi Key Laboratory of Macromolecular Science and Technology, Xi'an Key Laboratory of Hybrid Luminescent Materials and Photonic Device, School of Chemistry and Chemical Engineering, Northwestern Polytechnical University, Xi'an, 710129, China.
Small. 2025 Jun;21(24):e2502839. doi: 10.1002/smll.202502839. Epub 2025 Apr 26.
Inherent transparency makes epoxy resins ideal for aircraft windows, yet their brittleness and flammability remain challenges. Existing strategies for these issues often compromise transparency, with limited research on the mechanisms involved. Herein, a novel strategy is proposed for fabricating transparent epoxy resin by tuning the electrostatic potential distribution via hyperbranched polyborophosphate. Electron-deficient boron and relatively electron-rich phosphorus atoms work synergistically to increase the highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) energy gap, preventing visible light absorption. Meanwhile, the hyperbranched structure facilitates polymer network interpenetration to reduce porosity for decreased light scattering. This synergy results in a nearly colorless material with over 80% transmittance at 550 nm even at 4 mm thickness, along with full-band UV shielding. Notably, the material demonstrates a 114.7% increase in impact toughness (45.2 kJ m) due to dual dynamic B─O and P─O linkages. Besides, it yields a limiting oxygen index of 33% and a V0 rating in the underwriter laboratories vertical burning test, along with significant reductions in heat, smoke, and toxic gas release. The outstanding performance makes it stand out compared to reported advanced transparent epoxy resins, highlighting the significance of this work.
固有的透明度使环氧树脂成为飞机窗户的理想材料，但其脆性和易燃性仍然是挑战。针对这些问题的现有策略往往会损害透明度，且对相关机制的研究有限。在此，提出了一种通过超支化聚硼磷酸盐调节静电势分布来制备透明环氧树脂的新策略。缺电子的硼原子和相对富电子的磷原子协同作用，增加最高占据分子轨道-最低未占据分子轨道（HOMO-LUMO）能隙，防止可见光吸收。同时，超支化结构促进聚合物网络互穿，以降低孔隙率，减少光散射。这种协同作用产生了一种几乎无色的材料，即使在4毫米厚度下，在550纳米处的透光率也超过80%，同时具有全波段紫外线屏蔽性能。值得注意的是，由于双动态B─O和P─O键，该材料的冲击韧性提高了114.7%（45.2千焦/平方米）。此外，它的极限氧指数为33%，在保险商实验室垂直燃烧试验中达到V0等级，同时热释放、烟雾释放和有毒气体释放显著减少。与已报道的先进透明环氧树脂相比，其出色的性能使其脱颖而出，突出了这项工作的重要性。
