具有负泊松效应的智能防护复合材料

In our proposal, the impact hardening polymer (IHP) with stress-responsive and self-healing ability in ambient (low) temperature can be prepared utilizing dynamic cross-linking mechanism and structural design of flexible polymer backbone, in which reversible dynamic boron cross-linking junctions and the reduction of the threshold of entanglement density owing to bottlebrush/network structure of flexible polymeric backbone are employed to grant self-healing ability in ambient (low) temperature and energy absorbance property to materials. On the other hand, the characteristic relaxation time flexible polymeric backbone is far longer than the characteristic time arising from transient associating boron linkages. This huge difference in characteristic time scale endows impact hardening property into IHP. Meanwhile, the Poisson’s ratio of IHP can be negative or positive, and it fluctuates depending on external force that material undergoes. The home of idealized impact protective composite materials can be realized by employing IHP with various Poisson’s ratio as the first phase and elastic material with negative/positive Poisson’s ratio as the second phase. In the design of smart impact protective composite materials, their stress-responsive can be provided by dynamic negative Poisson’s ratio of IHP and their fatigue resistance can be improved by self-healing property of IHP. On the other hand, their shape-stabilized capability and energy absorption efficiency can be improved by the presence of the second continuous phase. Meanwhile, the Poisson’s ratio of materials is selected as the main research objective during the fabrication and investigation of IHPs and smart impact protective composite materials for the first time. Moreover, the reason of the formation, evolution discipline and regulating mechanism of negative Poisson’s ratio effect are elucidated in detail. Based on the comprehensive understanding of the correlation between evolution law of Poisson’s ratio of IHP and composite materials and their performance, the idealized impact protective composite materials can be designed in our proposal. Finally, the protective composite fabrics containing IHP and 3D space woven fabric, and impact protective composite materials are also prepared to use as smart impact protective materials. And their application performances are also another research aim in this proposal. Herein, our research will develop up a new perspective on impact protective materials by combining dynamic negative Poisson’s ratio effect with design concept of smart materials.

申请结合柔性链分子结构设计和动态交联机制制备具外力敏感性和常（低）温自修复特性的冲击硬化聚合物（IHP）。利用瓶刷或网络型柔性分子链结构对体系最低链缠结密度的降低作用和硼的动态交联改善材料常（低）温自愈合和能量吸收特性。利用柔性链松弛时间和硼动态交联特征时间之间的尺度差异赋予材料冲击硬化特性。通过材料结构参数调整，其泊松比可随外界条件在正值和负值之间自由调控。进而以IHP为主体，以具有正（负）泊松比的三维织物或弹性材料为第二相，通过不同配合方式构建智能防护复合材料。利用负泊松效应保证材料外力敏感性，自愈合性改善材料耐疲劳性。引入第二相改善材料形状保持能力及能量吸收效率，实现理想防护材料的智能化设计。同时提出将泊松比作为研究对象，通过考察IHP和复合材料泊松比的结构影响因素、演变规律和调控机理，最终制备泊松比可自主调控的智能防护复合材料，为冲击防护材料提供新的智能化研究和应用方向。

研究从主链结构设计出发，利用具有线型和支化结构的柔性羟基封端的聚二甲基硅氧烷（PDMS-OH）作为柔性主链，以三甲氧基硼氧六环 (TMOB) 中硼为动态交联中心，加入异佛尔酮二异氰酸酯 (IPDI)作为稳态化学中心和扩链剂，制备兼具良好外力敏感特性和常（低）温自愈合特性的冲击硬化材料（impact hardening polymer, IHP材料 ）。研究发现：材料体系内硼化合物与柔性主链羟基之间的动态交联是材料实现低温自愈合的主要原因，而主链在低温条件下良好的柔顺性也是材料可以实现低温自愈合的重要保证。IHP材料由于在小形变区间内分子结构内B-O键形成六元环状动态交联结构，阻碍了柔性分子链规整排列。同时六元环状结构使得材料在垂直于应力方向的尺度上发生轻微膨胀，导致材料泊松比为负（-1.0-0左右）。研究以三维空间织物为载体，将IHP材料通过浸涂整理的方式制备智能防护织物，防护织物具有优异的冲击防护性能。在冲击能量为50 J的冲击测试中，被传递力值最低仅有9.3 KN，能量吸收效率高达81%，超过欧盟运动防护用具的相关标准。.为了解决IHP材料冷流和高速冲击破碎的缺陷，研究采用IHP材料为第一相，以聚氨酯网络为第二相，合成双网络结构本体型智能防护材料。材料具有优异的自愈合性能和外力敏感性，在较宽温度范围内都具有良好的阻尼性能（在-60℃到60℃的范围内内耗始终大于0.3）。同时材料在室温下放置15天后尺寸变形幅度小于2%，显示出良好的尺寸稳定性。抗冲击测试表明，材料在冲击能量为50 J的冲击测试中能量吸收效率可达到65%，且在超过15m/s的高速冲击下不会发生破碎。同时研究也通过互穿网络原位合成的方法开发了PDMS-IHP、PAAm-IHP复合材料体系，拓宽了IHP材料的应用领域。