基于仿生强界面作用的多晶型含能材料相变抑制与机制研究

Phase transition leads to the increase of sensitivity and decrease of energy performance, which is the one of the bottleneck problems that limits the stability of the polymorphic energetic materials. Up to date, how to efficiently suppressing the phase transition is still a big challenge. The kinetics and mechanism of solid-solid phase transitions remain poorly understood. Stimulated by these open questions and technical difficulties, in the proposed project, the phase transition of two typical polymorphic energetic crystals, HMX and CL-20, will be suppressed by surface polymerization of dopamine, inspired by the strong chemical adhesion of mussels. On one hand, polymerization of dopamine will be introduced to coat energetic organic crystals and suppress the thermal phase transition. On the other hand, the dopamine molecule will be firstly modified with initiator by the reaction between –NH2 in dopamine and the initiator; then, the energetic crystals will be coated by polymerization of dopamine-initiator; lastly, the surface of the energetic crystals will be functionalized by grafting with polymers from those active initiator sites. By grafting with heat and solvent resistant polymers, the phase transition induced by heat and solvent can be efficiently suppressed. Combing the effects of the interfacial interaction and surface properties on the phase transition characteristics and kinetics, the mechanism of inhibition of phase transition of energetic crystals will be discussed. This project will provide new route for suppressing the phase transition of energetic crystals by strong interfacial interaction and surface functionalization based on the bio-inspired dopamine chemistry, furthermore, provide reference for exploring thermostable high energetic materials.

相变导致感度增加，能量下降，是制约多晶型含能材料稳定性的关键瓶颈问题。目前，对于相变抑制机制认识还不足,有效抑制多晶型含能材料相变仍然是一大挑战。结合仿生多巴胺化学的新发展，基于多巴胺对材料表面的强力粘附作用和可扩展的反应平台特征，本项目提出利用多巴胺与含能晶体强界面作用抑制相变。一方面，采用多巴胺氧化自聚合对含能晶体包覆形成强界面作用的核壳型结构，有望抑制含能晶体的热致相变；更进一步的策略是，将多巴胺分子先与引发剂反应，生成含引发剂的多巴胺，再在含能晶体表面氧化聚合包覆，最后，利用引发剂活性位点上引发聚合接枝阻热和溶剂的高分子，使含能晶体进一步表面功能化，抑制在热和溶剂复合作用下的相变。结合表界面结构对相变动力学的影响规律研究，深入探讨含能晶体相变抑制机制。本项目提出的基于仿生多巴胺的表面功能化途径可为含能晶体表面调控和晶相稳定提供新思路，并为研制耐热性能优异的高能含能材料提供参考。

相变是制约多晶型含能材料稳定性关键瓶颈问题，高效抑制相变具有挑战。为提升炸药热稳定性，基于多巴胺强粘附作用和反应平台特征，本项目开展基于仿生强界面作用的多晶型含能材料相变抑制与机制研究。主要开展多巴胺在含能晶体表面的氧化聚合及对相变的影响；基于多巴胺的含能晶体表面接枝功能化及相变抑制研究；含能晶体相变动力学及相变抑制机制研究；基于强界面作用的炸药相变抑制机制的验证等4个研究内容。.利用多巴胺氧化聚合包覆，实现HMX相变高效抑制。1.5%聚多巴胺（PDA）使HMX相变从192℃提高到247℃（10%氟粘结剂包覆仅提高5℃），并使炸药经200℃保持完整；采用甲基丙烯酰多巴胺(MDA)、甲基丙烯酰胺(MA)和丙烯酸(AA)共聚包覆同时抑制热致相变降低机械感度。.在PDA包覆基础上，采用原子转移自由基聚合成功在CL-20表面接枝功能化并提升其溶剂热稳定性。在90℃体积比为1:4水/无水乙醇中120min，CL-20、CL-20@PDA和PNIPAM接枝CL-20（接枝量为1.1%）分别有94.2%、67%和22.6%的ε相转为α相；PDA对溶剂有一定阻隔作用，PNIPAM进一步减少高温溶剂分子与CL-20接触，有效抑制溶剂诱导，从而抑制相变。.以HMX和HMX@PDA（HP-4）为典型，获得非等温和等温相变动力学，基于Logistic函数优化了等温相变动力学模型。HMX在179℃~183℃成核和增长速率常数分别为10-5s-1和10-3s-1；HP-4在212℃~224℃分别为10-9s-1和10-3s-1。通过理论模拟和实验，获得PDA对HMX相变抑制机制，PDA与HMX强界面作用抑制分子构象转变进而抑制成核。.基于强界面作用的炸药相变抑制机制被金属多酚网络包覆、溶菌酶包覆、晶体共颗粒组装、一核双壳结构等技术途径进一步验证。本项目可为提升含能材料的热稳定性和武器系统安全性提供技术支撑。