基于金属-配体络合作用的多响应PPDO-PEG动态交联网络的制备及其形状记忆和自修复行为研究

In recent years, multiple response, multiple shape and multiple functionality become the new trend in the research field of the shape memory polymers. For the architecture design of the multiple shape polymers, the traditional polymer networks based on covalent bond were widely used, however,this type of network has its own limitation in processing compared with thermoplastic polymers. Recently, a new concept of utilizing reversible non-covalent bond to construct dynamic reversible network has been highly concerned.Among the various non-covalent bond such as hydrogen bond,π-π stacking,gest-host interaction, hydrophobic interaction and so on,metal-ligand coordination is most attractive owing to its high bond energy,multi-responsibility and reversibility with high efficiency. This project aims to develop a novel poly(p-dioxanone)-poly(ethylene glycol) dynamic crosslink network based on metal-ligand coordination (ML-PDEG), and the architecture of polymer networks could be well-defined by varying the type of metal ions and ligand, polymer precursors and the synthetic route. Accordingly, the metal-ligand coordination bond can be act as netpoints in the shape-memory mode,meanwhile,the PPDO and PEG segments can be act as the reversible phases, material may show thermally-induced triple shape effect. Furthermore, the metal-ligand coordination bond also can be serve as the molecular switch in the shape-memory mode while PPDO serve as fixing phase, then, the material exhibits light-induced shape memory effect. More important, it also plays an important role to trigger the self-healing behaviors. The inflence of architecture of the networks, the influence of distribution and the density of the metal-ligand coordination points in the hard and soft segments on the shape-memory effects and the self-healing performance will be investigated systematically. This smart material combines the virtue of excellent performance of dynamic network both on shape-memory polymers and self-healing materials, which will broaden the scope of applications of this novel dynamic networks.

近年来，形状记忆高分子材料已向多刺激响应、多重形状记忆和多功能化方向发展。本项目拟采用金属-配体络合作用，将链段中含有多个联二吡啶双齿配体的聚对二氧环己酮(PPDO)-聚乙二醇(PEG)线性多嵌段共聚物通过与金属离子络合构筑ML-PDEG动态交联网络。利用金属-配体络合作用较高的键合强度，络合交联点可充当形状记忆材料的固定相，PPDO和PEG链段充当可逆相，材料可显示出热致三重形状记忆行为；而利用金属-配体络合作用的动态可逆性，络合交联点又可充当形状记忆材料的分子开关，PPDO链段充当固定相，通过紫外光控程序启动金属-配体络合作用的解离和再键合，材料可显示出光致形状记忆行为；在材料受到破坏时，这种动态可逆性又可赋予材料自修复功能。研究PPDO和PEG的共聚比例、配体在共聚物中的分布方式及密度、金属离子种类对材料形状记忆性能和自修复性能的影响，制备出综合性能优异的新型多功能智能材料。

近年来，形状记忆高分子材料(SMPs)已向多刺激响应、多重形状记忆和多功能化方向发展。然而，传统的热固性SMPs因其固有特性而存在不能反复加工、链段结晶受限等缺陷，而基于结晶及大分子缠绕作用的热塑性SMPs又存在着力学性能及形状回复性能差等问题。利用超分子作用特别是键能大、条件温和且过程可逆的金属配位作用来构建SMPs网络，可有效的解决上述难题。本项目将金属-配体络合相互作用成功应用到形状记忆高分子材料的结构设计中，合成了出一系列不同结构的形状记忆动态交联网络，并利用其动态性质，赋予材料优异的自修复性能和可重复加工性。其中包括了（1）以PPDO链段为分子开关、联吡啶为配体、与二价铁离子配位形成的热响应形状记忆动态网络，该动态网络具有优异的力学性能、形状记忆性能和可反复加工性能；在此基础上进一步引入第二分子开关PEG链段，获得了三重形状记忆动态网络。（2）受海洋生物贻贝启发，利用儿茶酚基团与四氧化三铁纳米颗粒（Fe3O4 NPs）的超强络合相互作用设计制备了单/双向形状记忆PCL复合材料，利用Fe3O4 NPs的超顺磁性和近红外光吸收性能实现了材料的热、磁、光等多重响应形状记忆行为，利用PCL链段的结晶诱导伸长和熔融诱导收缩实现材料的双向形状记忆性能，借助网络的动态性，赋予材料优异的自修复性能；在此基础上，通过引入第二结晶链段聚四氢呋喃（PTMEG）和并经合理的程序设置固定其内应力，该材料具备了无应力条件下的双向形状记忆性能。（3）利用聚乙烯醇的羟基与二价铜离子之间的配位相互作用制备了PVA-Cu/Sep自修复水凝胶，通过引入纤维状纳米粒子海泡石实现对材料的增强和增韧。（4）此外，本项目还利用蒽的光可逆反应设计制备了光响应、光交联形状记忆材料。系统研究了材料结构与性能的关系，为形状记忆高分子材料和自修复材料的设计提供了新的思路。