Tough Self-Healing Elastomers by Molecular Enforced Integration of Covalent and Reversible Networks.
Tough Self-Healing Elastomers by Molecular Enforced Integration of Covalent and Reversible Networks.
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通过共价和可逆网络的分子强制整合实现坚韧的自修复弹性体
DOI：
10.1002/adma.201702616
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发表时间：
2017-10
期刊：
影响因子：
--
通讯作者：
Weitz DA
中科院分区：
文献类型：
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作者：
Wu J;Cai LH;Weitz DA
由完全可逆键交联的自修复聚合物本质上比普通的共价交联网络弱。将共价交联引入可逆网络将提高机械强度。然而，将这一概念应用于Dry弹性体是具有挑战性的，主要是因为可逆交联物，如氢键，通常是极性基序，而共价交联物是非极性基序。这两种类型的键在没有共溶剂的情况下本质上是不相容的。在这里，我们设计并制造了一种杂化聚合物网络，通过将随机支化的聚合物进行交联，携带的基序既可以形成可逆的氢键，也可以形成永久的共价交联。这种随机支化的聚合物连接了这两种类型的键，并迫使它们在没有共溶剂的情况下在分子水平上混合。这使我们能够创造出一种非常坚韧的混合“干”弹性体，其断裂能为13,500J/m2，与天然橡胶相当。此外，该弹性体可以在室温下自愈合，拉伸强度恢复到4 Mpa，是其原始值的30%，但与现有自愈合聚合物的原始强度相当。迫使共价键和可逆键在分子水平混合以创建均一网络的概念是非常普遍的，应该能够开发出具有实际用途的坚韧、自修复的聚合物。一种坚韧的、自我修复的聚合物网络是通过将随机支化的聚合物进行交联而制成的，这些聚合物携带的基序既可以形成可逆的氢键，也可以形成永久的共价交联。随机支化的聚合物迫使这两种类型的键在分子水平上混合，而不需要共溶剂；这使得混合型“干”弹性体具有出色的韧性和自愈能力的组合。
Self-healing polymers crosslinked by solely reversible bonds are intrinsically weaker than common covalently crosslinked networks. Introducing covalent crosslinks into a reversible network would improve mechanical strength. It is challenging, however, to apply this concept to‘dry’ elastomers, largely because reversible crosslinks such as hydrogen bonds are often polar motifs, whereas covalent crosslinks are non-polar motifs. These two types of bonds are intrinsically immiscible without co-solvents. Here we design and fabricate a hybrid polymer network by crosslinking randomly branched polymers carrying motifs that can form both reversible hydrogen bonds and permanent covalent crosslinks. The randomly branched polymer links such two types of bonds and forces them to mix on the molecular level without co-solvents. This allows us to create a hybrid ‘dry’ elastomer that is very tough with a fracture energy 13,500J/m2 comparable to that of natural rubber. Moreover, the elastomer can self-heal at room temperature with a recovered tensile strength 4MPa, which is 30% of its original value, yet comparable to the pristine strength of existing self-healing polymers. The concept of forcing covalent and reversible bonds to mix at molecular scale to create a homogenous network is quite general and should enable development of tough, self-healing polymers of practical usage. A tough, self-healing polymer network is fabricated by crosslinking randomly branched polymers carrying motifs that can form both reversible hydrogen bonds and permanent covalent crosslinks. The randomly branched polymer forces such two types of bonds to mix on the molecular level without co-solvents; this enables a hybrid ‘dry’ elastomer that with an exceptional combination of toughness and self-healing ability.