Li Min, Zhou Xin, Han Dandan, Zhang Qi, Li Xiaodong, Li Hongzhen, Gong Junbo
State Key Laboratory of Chemical Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300072, P. R. China.
Collaborative Innovation Center of Chemistry and Chemical Engineering, Tianjin, 300072, P. R. China.
Small. 2024 Oct;20(40):e2400970. doi: 10.1002/smll.202400970. Epub 2024 May 27.
The fabrication of materials with hierarchical structures has garnered great interest, owing to the potential for significantly enhancing their functions. Herein, a strategy of coupling molecular solvation and crystal growth is presented to fabricate porous spherulites of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20), an important energetic material. With the addition of polyvinylpyrrolidone in the antisolvent crystallization, the metastable solvate of CL-20 is formed and grows spherulitically, and spontaneously desolvates to obtain the porous spherulite when filtration, in which the characteristic peak of the nitro group of CL-20 shifts detected by the in situ micro-confocal Raman spectroscopy. The effect of polyvinylpyrrolidone is thought to induce the solvation of CL-20, confirmed by density functional theory calculations, meanwhile acting on the (020) face of CL-20 to trigger spherulitic growth, demonstrated through infrared spectroscopy and Rietveld refinement of powder X-ray diffraction. Moreover, compared to common CL-20 crystals, porous spherulites exhibit enhanced combustion with increases of 6.24% in peak pressure, 40.21% in pressurization rate, and 9.63% in pressure duration effect, indicating the capability of hierarchical structures to boost the energy release of energetic crystals. This work demonstrates a new route via solvation-growth coupling to construct hierarchical structures for organic crystals and provides insight into the structure-property relations for material design.
具有分级结构的材料制备因其显著增强功能的潜力而备受关注。在此，提出了一种分子溶剂化与晶体生长耦合的策略，用于制备2,4,6,8,10,12-六硝基-2,4,6,8,10,12-六氮杂异伍兹烷（CL-20）的多孔球晶，CL-20是一种重要的含能材料。在反溶剂结晶过程中加入聚乙烯吡咯烷酮，形成CL-20的亚稳溶剂化物并球状生长，过滤时自发去溶剂化得到多孔球晶，其中原位微共焦拉曼光谱检测到CL-20硝基特征峰发生位移。聚乙烯吡咯烷酮的作用被认为是诱导CL-20的溶剂化，密度泛函理论计算证实了这一点，同时作用于CL-20的（020）面触发球状生长，红外光谱和粉末X射线衍射的Rietveld精修证明了这一点。此外，与普通CL-20晶体相比，多孔球晶的燃烧性能增强，峰值压力提高6.24%，增压速率提高40.21%，压力持续时间效应提高9.63%，表明分级结构能够促进含能晶体的能量释放。这项工作展示了一种通过溶剂化-生长耦合构建有机晶体分级结构的新途径，并为材料设计的结构-性能关系提供了见解。
