Thiophene-Rich Benzoxazines with an Amide Moiety: Integration of Structural and Hydrogen Bonding Influence on the Polymerization Mechanism by Experimental and Computational Studies
Thiophene-Rich Benzoxazines with an Amide Moiety: Integration of Structural and Hydrogen Bonding Influence on the Polymerization Mechanism by Experimental and Computational Studies
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DOI：
10.1021/acs.macromol.3c01515
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发表时间：
2023-08
期刊：
影响因子：
5.5
通讯作者：
Nan Li;Shengfu Yang;Kan Zhang
中科院分区：
文献类型：
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作者：
Nan Li;Shengfu Yang;Kan Zhang
苯并恶嗪热固性树脂作为高级高分子材料的未来发展取决于设计出更有吸引力的化学结构，并在分子水平上对结构-性能关系有更深入的了解。在此，我们合成了一系列新的苯并恶嗪，这些苯并恶嗪环上的氧在邻位和对位具有噻吩乙酰胺或噻吩乙酰胺的官能团。通过傅里叶变换红外光谱（FT-IR）、核磁共振（NMR）和高分辨率质谱分析，成功合成了富噻吩的苯并恶嗪单体，并对其进行了分子表征。采用差示扫描量热法、原位红外光谱和热重分析等方法研究了苯并恶嗪开环聚合过程及其聚苯并恶嗪的热性能。此外，利用一维和二维核磁共振以及密度泛函理论计算的结合实验和计算研究为结构和氢键对聚合机理的影响提供了动力学见解。通过对这些新型苯并恶嗪中氢键的设计，发现在强氢键的恶嗪环上的氧可以生成相对较弱的o - 2键，从而降低开环聚合温度。本研究的基础研究使我们对苯并恶嗪中的氢键相互作用及其在聚合行为中的作用有了更深入的了解。此外，这些新获得的富含噻吩的苯并恶嗪也为我们开发具有前景的高性能聚苯并恶嗪热固性材料提供了充足的机会。
The future development of benzoxazine thermosetting resins as advanced polymeric materials depends on designing more attractive chemical structures and reaching a deeper understanding of the structure–property relationship at the molecular level. Herein, we synthesized a new series of benzoxazines containing the thiophenecarboxamide or thiopheneacetamide functionality at the ortho- and para-positions with respect to oxygen in the oxazine ring. Successful syntheses of thiophene-rich benzoxazine monomers and their corresponding molecular characterizations were confirmed by Fourier transform infrared (FT-IR) spectroscopy, nuclear magnetic resonance (NMR), and high-resolution mass spectroscopy. Ring-opening polymerization processes of benzoxazines and thermal properties of their resulting polybenzoxazines were studied by differential scanning calorimetry, in situ FT-IR spectroscopy, and thermogravimetric analysis. In addition, a combined experimental and computational study using both 1D and 2D NMR as well as density functional theory calculations provided kinetic insights into the effects of structural and hydrogen bonding on the polymerization mechanism. With the designed varieties of hydrogen bonds in these novel benzoxazines, it has been found that oxygen in the oxazine ring involved in stronger hydrogen bonding can generate a relatively weaker O–CH2bond, leading to the reduced ring-opening polymerization temperature. The fundamental investigations presented in the current work provide us a deeper understanding of the hydrogen bonding interaction in benzoxazine as well as its role in polymerization behavior. Moreover, these newly obtained thiophene-rich benzoxazines also give us ample opportunities to develop high-performance polybenzoxazine thermosets with promising applications.