Department of Chemistry, Duke University, Durham, North Carolina 27708, USA.
Nat Chem. 2013 Sep;5(9):757-61. doi: 10.1038/nchem.1720. Epub 2013 Aug 4.
High shear stresses are known to trigger destructive bond-scission reactions in polymers. Recent work has shown that the same shear forces can be used to accelerate non-destructive reactions in mechanophores along polymer backbones, and it is demonstrated here that such mechanochemical reactions can be used to strengthen a polymer subjected to otherwise destructive shear forces. Polybutadiene was functionalized with dibromocyclopropane mechanophores, whose mechanical activation generates allylic bromides that are crosslinked in situ by nucleophilic substitution reactions with carboxylates. The crosslinking is activated efficiently by shear forces both in solvated systems and in bulk materials, and the resulting covalent polymer networks possess moduli that are orders-of-magnitude greater than those of the unactivated polymers. These molecular-level responses and their impact on polymer properties have implications for the design of materials that, like biological materials, actively remodel locally as a function of their physical environment.
高剪切应力已知会引发聚合物中的破坏性键断反应。最近的研究表明，相同的剪切力可用于加速机械敏感分子沿聚合物主链的非破坏性反应，并且这里证明这种机械化学反应可用于增强承受破坏性剪切力的聚合物。聚丁二烯用二溴环丙烷机械敏感分子官能化，其机械激活生成烯丙基溴，这些烯丙基溴通过与羧酸盐的亲核取代反应就地交联。在溶剂化体系和本体材料中，剪切力都能有效地激活交联，所得共价聚合物网络的模量比未激活的聚合物大几个数量级。这些分子水平的响应及其对聚合物性能的影响对于设计材料具有意义，这些材料像生物材料一样，根据其物理环境主动进行局部重塑。
