Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290, USA.
J Am Chem Soc. 2010 Sep 8;132(35):12487-91. doi: 10.1021/ja105897b.
Mechanical activation of chemical bonds typically involves the application of external forces, which implies a broad distribution of bond tensions. We demonstrate that controlling the flow profile of a macromolecular fluid generates and delineates mechanical force concentration, enabling a hierarchical activation of chemical bonds on different length scales from the macroscopic to the molecular. Bond tension is spontaneously generated within brushlike macromolecules as they spread on a solid substrate. The molecular architecture creates an uneven distribution of tension in the covalent bonds, leading to spatially controlled bond scission. By controlling the flow rate and the gradient of the film pressure, one can sever the flowing macromolecules with high precision. Specific chemical bonds are activated within distinct macromolecules located in a defined area of a thin film. Furthermore, the flow-controlled loading rate enables quantitative analysis of the bond activation parameters.
机械激活化学键通常涉及外力的施加，这意味着键张力的广泛分布。我们证明，控制高分子流体的流动形态可以产生和描绘机械力集中，从而在从宏观到分子的不同长度尺度上实现化学键的分级激活。当刷状高分子在固体基底上展开时，会在其内部分子链中自发产生键张力。分子结构导致共价键中的张力分布不均匀，从而导致空间控制的键断裂。通过控制流速和膜压梯度，可以高精度地切断流动的高分子。可以在薄膜的特定区域内定位的特定高分子中激活特定化学键。此外，流控加载速率可以实现对键激活参数的定量分析。
