大分子复合物中应力诱导链邻近的直接证据
Direct evidence of stress-induced chain proximity in a macromolecular complex
摘要：
许多超分子材料的机械性能通常由化学组成和分子微观结构组织之间的相互作用产生的非共价相互作用决定。非共价相互作用的可逆性质赋予了超分子材料以其他方式难以获得的响应性质，例如作为对机械应力的响应而变得刚性。非共价相互作用究竟是如何从微观结构中产生的，它们如何响应施加的力或变形而变化，目前还不清楚。在这里，我们结合核磁共振（NMR）和流变学直接探测的作用，在聚合物复合物的链接近。我们观察到链的接近度增加，在响应强加的流量，我们假设这是源于增强的氢键。链的接近度与爬杆和剪切带直接相关。只有当施加的应力较低时，流动才会持续，这表明应力诱导的增厚机制。我们验证了氢键破坏剂可以关闭非平凡的流动行为和链邻近的光谱证据。结合流变-核磁共振方法表明，它是可能的，直接观察超分子力学背后的分子起源，为进一步研究超分子材料的机械化学性质铺平了道路。
英文摘要：
The mechanical properties of many supramolecular materials are often determined by non-covalent interactions that arise from an interplay between chemical composition and molecular microstructural organization. The reversible nature of non-covalent interactions gives supramolecular materials responsive properties that are otherwise difficult to obtain, such as becoming rigid as a response to mechanical stress. How exactly non-covalent interactions emerge from microstructure, how they might change in response to applied force or deformation is not understood. Here we combine Nuclear Magnetic Resonance (NMR) and rheology to directly probe the role of chain proximity in polymer complexes. We observe an increase in chain proximity in response to imposed flow, which we hypothesize to originate from enhanced hydrogen bonding. The chain proximity is directly correlated to rod climbing and shear banding. Flow persists only when applied stresses are low, suggesting a stress-induced thickening mechanism. We verify that hydrogen bond disruptors can turn off both the non-trivial flow behavior and the spectroscopic evidence of chain proximity. The combined rheo-NMR approach shows that it is possible to directly observe the molecular origins behind supramolecular mechanics, paving the way for further study into mechano-chemical properties of supramolecular materials.
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