Adsorption-induced scission of carbon-carbon bonds
Adsorption-induced scission of carbon-carbon bonds
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DOI：
10.1038/nature04576
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发表时间：
2006-03-09
期刊：
影响因子：
64.8
通讯作者：
Matyjaszewski, K
中科院分区：
文献类型：
--
作者：
Sheiko, SS;Sun, FC;Matyjaszewski, K
碳-碳共价键很难断裂。它们的强度在金刚石的硬度（1，2）和聚合物纤维的拉伸强度（3-6）中是明显的;在单分子水平上，它表现为需要几个纳米牛顿的力来延伸和机械地断裂一个键。已经使用拉伸流（7-9）、超声辐射（10）、后退弯月面（11）和通过用纳米探针直接拉伸单个分子（12-16）来产生这种力。在这里，我们表明，刷状大分子与长侧链在基板上的简单吸附不仅可以诱导构象变形（17），而且在大分子骨架中的共价键的自发断裂。我们将这种行为归因于这样的事实，即侧链和基底之间的吸引力相互作用通过侧链的扩展而最大化，这又引起沿沿着聚合物主链的张力。只要侧链密度和底物相互作用足够高，产生的张力将足够强，足以破坏碳碳共价键。我们预计类似的吸附诱导的主链断裂发生的所有大分子与高度支化的架构，如刷和树枝状聚合物。当设计这种类型的表面靶向大分子时，需要考虑这种行为，以避免不期望的降解，或确保在预定的大分子位点处破裂。
Covalent carbon-carbon bonds are hard to break. Their strength is evident in the hardness of diamonds(1,2) and tensile strength of polymeric fibres(3-6); on the single-molecule level, it manifests itself in the need for forces of several nanonewtons to extend and mechanically rupture one bond. Such forces have been generated using extensional flow(7-9), ultrasonic irradiation(10), receding meniscus(11) and by directly stretching a single molecule with nanoprobes(12-16). Here we show that simple adsorption of brush-like macromolecules with long side chains on a substrate can induce not only conformational deformations(17), but also spontaneous rupture of covalent bonds in the macromolecular backbone. We attribute this behaviour to the fact that the attractive interaction between the side chains and the substrate is maximized by the spreading of the side chains, which in turn induces tension along the polymer backbone. Provided the side-chain densities and substrate interaction are sufficiently high, the tension generated will be strong enough to rupture covalent carbon-carbon bonds. We expect similar adsorption-induced backbone scission to occur for all macromolecules with highly branched architectures, such as brushes and dendrimers. This behaviour needs to be considered when designing surface-targeted macromolecules of this type either to avoid undesired degradation, or to ensure rupture at predetermined macromolecular sites.