Embrechts Anika, Schönherr Holger, Vancso G Julius
Faculty of Science and Technology, MESA+ Institute for Nanotechnology, Department of Materials Science and Technology of Polymers, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands.
J Phys Chem B. 2008 Jun 26;112(25):7359-62. doi: 10.1021/jp803260n. Epub 2008 May 30.
Atomic-force-microscopy-based single-molecule force spectroscopy (AFM-SMFS) was used to study the bond strength of self-complementary hydrogen-bonded complexes based on the 2-ureido-4[1H]-pyrimidinone (UPy) quadruple H-bond motif in hexadecane (HD). The unbinding force corresponding to single UPy-UPy dimers was investigated at a fixed piezo retraction rate in the nonequilibrium loading rate regime. The rupture force of bridging supramolecular polymer chains formed between UPy-functionalized substrates and AFM tips in the presence of a bis-UPy derivative was found to decrease with increasing rupture length. The rupture length was identified as the chain length of single, associating polymers, which allowed us to determine the number of supramolecular bonds (N) at rupture. The rupture force observed as a function of N was in quantitative agreement with the theory on uncooperative bond rupture for supramolecular linkages switched in a series. Hence, the value of the dimer equilibrium constant Keq=(1.3+/-0.5) x 10(9) M(-1), which is in good agreement with previously estimated values, was obtained by SMFS of supramolecular polymers at a single loading rate.
基于原子力显微镜的单分子力谱（AFM-SMFS）被用于研究基于十六烷（HD）中2-脲基-4[1H]-嘧啶酮（UPy）四重氢键基序的自互补氢键复合物的键强度。在非平衡加载速率条件下，以固定的压电回缩速率研究了单个UPy-UPy二聚体对应的解离力。发现在双UPy衍生物存在的情况下，UPy功能化底物与AFM探针之间形成的桥连超分子聚合物链的断裂力随断裂长度的增加而降低。断裂长度被确定为单个缔合聚合物的链长，这使我们能够确定断裂时超分子键的数量（N）。观察到的断裂力作为N的函数与串联切换的超分子键合的非协同键断裂理论在定量上一致。因此，通过在单一加载速率下对超分子聚合物进行SMFS，获得了二聚体平衡常数Keq=(1.3±0.5)×10(9) M(-1)，这与先前估计的值非常吻合。
