Chain‐end functionalized polybutadiene polymers have widespread application in composite solid propellants (CSP). Curing of these polymers is effected using the reactions at the terminal groups with isocyanates or aziridines if the functional groups are hydroxyl or carboxyl respectively. The high toxicity of isocyanates and aziridines demands alternate cure methods. A facile reaction, devoid of any side reactions is the most desirable one. The large number of double bonds in polybutadienes is favorable for 1, 3 ‐dipolar addition reaction with an azide to yield triazolines. The mechanistic aspects of the uncatalyzed and copper‐mediated azide‐alkene reaction have not been explored previously. The present study focuses on elucidation of the reaction using model compounds of polybutadiene namely trans 3‐hexene, cis‐3 hexene and 3‐methyl pentene which mimic the microstructure of polybutadienes. The paper presents the elucidation of the mechanism using density functional theory (DFT) calculations, detailed reaction pathway and its experimental validation using Fourier transform infrared (FTIR) spectroscopy and ¹³C nuclear magnetic resonance (NMR) spectroscopy. DFT studies indicate that the activation barrier of 63.8 to 85 kJ/mol for the uncatalyzed reaction. In the copper catalyzed reaction, it diminishes to the range of 18.1 to 33.0 kJ/mol. The thermal decomposition aspects of the cured triazoline system were evaluated using thermogravimetric‐mass spectrometer (TG‐MS). The binder undergoes single stage decomposition in the temperature regime of 278°C‐534°C which is lower than that reported for polyurethane‐polybutadienes. The decomposition reaction yields more volatile products like nitrogen, carbon dioxide, 1,4 butadiene and 4‐vinylcyclohexene, conducive for propellant applications.

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通过三唑啉杂环轻松交联聚丁二烯：破译机理和结构性质关系

链端官能化聚丁二烯聚合物在复合固体推进剂（CSP）中具有广泛的应用。如果官能团分别为羟基或羧基，则使用末端基团与异氰酸酯或氮丙啶的反应来实现这些聚合物的固化。异氰酸酯和氮丙啶的高毒性需要替代的固化方法。最理想的反应是没有任何副反应的简便反应。聚丁二烯中大量的双键有利于与叠氮化物进行1,3-偶极加成反应生成三唑啉。以前尚未探讨过未催化和铜介导的叠氮化物-烯烃反应的机理。本研究着重于使用聚丁二烯模型化合物即反式3-己烯来阐明反应 顺式3己烯和3甲基戊烯，它们模拟了聚丁二烯的微观结构。本文介绍了使用密度泛函理论（DFT）计算，详细的反应途径以及使用傅里叶变换红外（FTIR）光谱和¹³ C核磁共振（NMR）光谱。DFT研究表明，未催化反应的活化势垒为63.8至85 kJ / mol。在铜催化的反应中，它减小到18.1至33.0kJ / mol的范围。使用热重质谱仪（TG-MS）对固化的三唑啉系统的热分解方面进行了评估。粘合剂在278°C-534°C的温度范围内经历了单阶段分解，低于聚氨酯-聚丁二烯的报道温度。分解反应会产生更多易挥发的产物，例如氮气，二氧化碳，1,4丁二烯和4-乙烯基环己烯，有利于推进剂的应用。