微胶囊自修复材料的修复反应

Healing Chemistry for Self-healing Material Based on Microcapsule

受自然界生物可以自动愈合伤口的启发,科学家设计出能够自动修复损伤的自修复材料。由于微胶囊体系的制备工艺简单、应用范围广、对多种损伤形式均可修复,受到了科学家的广泛关注。其主要修复过程为:裂纹扩展使微胶囊破裂,微胶囊内的修复剂流到微裂纹处,在催化剂作用下修复剂发生聚合反应从而修复微裂纹。这一过程中修复反应是实现材料自修复的关键,它必须能够在室温下将低粘度液体转变为坚韧的热固性高聚物。本文综述了针对微胶囊自修复材料的修复反应,重点介绍了环烯烃的开环易位聚合、环氧树脂的开环聚合、溶剂的再固化、点击化学四类反应。其中,点击化学由于简单高效的特点成为设计自修复材料的新方法,包括叠氮化物-炔烃反应、共轭二烯和亲二烯体反应、疏基-烯反应、疏基-氰酸酯反应等。通过对比分析修复反应的机理和自修复效率的影响因素,指出各种修复反应的优点和局限性,并对微胶囊自修复材料的发展趋势进行展望。

Inspired by biological system which can heal its wound, the self-healing material that can detect the damage and heal itself automatically has developed. Because of simple preparation process, widely application field and extensive healing types, the microcapsule-based system has attracted most research attentions. Its repair process is triggered by rupture of microcapsule when a crack propagates through the matrix, followed by release healing agent into the crack plane. Then the healing agent mixes with catalyst, bonds the crack through polymerization. The healing chemistry that can transform from low viscosity liquid into tough and hard thermoset is the key to facilitate healing process. This review summarizes the different chemistries used in state-of-the-art self-healing materials based on microcapsule, and mainly describes ring-opening metathesis polymerization of cyclic olefin, ring-opening polymerization reaction of epoxide, further curing reaction based on solvent and click chemistry. Moreover, the click chemistry becomes a particularly powerful method to design self-healing material because of its simple and efficient feature, including azide-alkyne reaction, Diels-Alder reaction, thiol-ene reaction and thiol-isocyanate reaction. The mechanism of self-healing chemistries and influence factors of self-healing efficiency are analyzed, and the limitations and benefits of the healing chemistry are discussed. Finally thechallenges and future opportunities are highlighted.