Phosphaphenanthrene-Functionalized Benzoxazines Bearing Intramolecularly Hydrogen-Bonded Phenolic Hydroxyl: Synthesis, Structural Characterization, Polymerization Mechanism, and Property Investigation
Phosphaphenanthrene-Functionalized Benzoxazines Bearing Intramolecularly Hydrogen-Bonded Phenolic Hydroxyl: Synthesis, Structural Characterization, Polymerization Mechanism, and Property Investigation
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DOI：
10.1021/acs.macromol.3c00028
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发表时间：
2023-02
期刊：
影响因子：
5.5
通讯作者：
Rui Yang;Nan Li;C. Evans;Shengfu Yang;Kan Zhang
中科院分区：
文献类型：
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作者：
Rui Yang;Nan Li;C. Evans;Shengfu Yang;Kan Zhang
热固性树脂中的氢键可以对聚合过程和相应热固性材料的性能产生重大影响，但其在苯并恶嗪树脂聚合中的作用仍不清楚。在这里，我们从2-6-氧化-6H-二苯并-[c,e][1,2]氧磷杂环-1,4-二羟基亚苯基、苯胺/糠胺和多聚甲醛合成了两种新型磷杂菲官能化苯并恶嗪单体，并通过1H、13C和31P NMR、傅里叶变换红外(FT-IR)、元素分析和高分辨率质谱研究了结构。然后通过差示扫描量热法（DSC）和原位傅立叶变换红外光谱研究了两种单体的开环聚合，所得热固性材料表现出高热稳定性和低可燃性。密度泛函理论（DFT）计算表明，两种单体的磷杂菲官能团中的酚-OH和P=O之间优选形成分子内氢键，这与实验结果一致。我们提出了一种阳离子激活的开环聚合机制，其中分子内氢键起着关键作用。实验和计算工作的结合为分子内氢键及其在苯并恶嗪化学聚合机制中的作用提供了分子水平的见解，并为高性能热固性聚合物的设计提供了新的角度。
Hydrogen bonding in thermosetting resins can have a significant influence on the polymerization processes and the properties of corresponding thermosets, but its role in the polymerization of benzoxazine resins remains unclear. Here, we synthesized two novel phosphaphenanthrene-functionalized benzoxazine monomers from 2-6-oxido-6H-dibenz-[c,e][1,2]oxaphosphorin-1,4-dihydroxy phenylene, aniline/furfurylamine, and paraformaldehyde and investigated the structures by1H,13C, and31P NMR, Fourier transform infrared (FT-IR), elemental analysis, and high-resolution mass spectrometry. Ring-opening polymerizations of both monomers were then studied by differential scanning calorimetry (DSC) andin situFT-IR spectroscopy, and the resulting thermosets exhibited high thermal stability and low flammability. Density functional theory (DFT) calculations suggested that intramolecular hydrogen bonds are preferably formed between the phenolic −OH and the P═O in the phosphaphenanthrene functionality for both monomers, which is in line with the experimental results. We proposed a cation-activated ring-opening polymerization mechanism where intramolecular hydrogen bonding plays a pivotal role. The combination of experimental and computational effort provides molecular-level insights into intramolecular hydrogen bonding and its role in polymerization mechanisms in benzoxazine chemistry as well as a new angle for the design of high-performance thermoset polymers.