Utzig Thomas, Raman Sangeetha, Valtiner Markus
Department of Interface Chemistry and Surface Engineering, Max-Planck-Institut für Eisenforschung GmbH , Max-Planck Straße 1, 40237 Düsseldorf, Germany.
Langmuir. 2015 Mar 10;31(9):2722-9. doi: 10.1021/la504542f. Epub 2015 Feb 23.
Understanding the evolution of macroscopic adhesion based on fundamental molecular interactions is crucial to designing strong and smart polymer/metal interfaces that play an important role in many industrial and biomedical applications. Here we show how macroscopic adhesion can be predicted on the basis of single molecular interactions. In particular, we carry out dynamic single molecule-force spectroscopy (SM-AFM) in the framework of Bell-Evans' theory to gain information about the energy barrier between the bound and unbound states of an amine/gold junction. Furthermore, we use Jarzynski's equality to obtain the equilibrium ground-state energy difference of the amine/gold bond from these nonequilibrium force measurements. In addition, we perform surface forces apparatus (SFA) experiments to measure macroscopic adhesion forces at contacts where approximately 10(7) amine/gold bonds are formed simultaneously. The SFA approach provides an amine/gold interaction energy (normalized by the number of interacting molecules) of (36 ± 1)k(B)T, which is in excellent agreement with the interaction free energy of (35 ± 3)k(B)T calculated using Jarzynski's equality and single-molecule AFM experiments. Our results validate Jarzynski's equality for the field of polymer/metal interactions by measuring both sides of the equation. Furthermore, the comparison of SFA and AFM shows how macroscopic interaction energies can be predicted on the basis of single molecular interactions, providing a new strategy to potentially predict adhesive properties of novel glues or coatings as well as bio- and wet adhesion.
基于基本分子相互作用来理解宏观粘附的演变对于设计强大且智能的聚合物/金属界面至关重要，这些界面在许多工业和生物医学应用中发挥着重要作用。在此，我们展示了如何基于单分子相互作用来预测宏观粘附。具体而言，我们在贝尔 - 埃文斯理论的框架内进行动态单分子力谱（SM-AFM），以获取有关胺/金结的结合态与非结合态之间能垒的信息。此外，我们利用雅尔津斯基等式从这些非平衡力测量中获得胺/金键的平衡基态能量差。另外，我们进行表面力仪（SFA）实验，以测量在同时形成约10⁷个胺/金键的接触处的宏观粘附力。SFA方法提供了一个（36 ± 1）k₈T的胺/金相互作用能（通过相互作用分子数归一化），这与使用雅尔津斯基等式和单分子AFM实验计算得到的（35 ± 3）k₈T的相互作用自由能高度吻合。我们的结果通过测量等式两边验证了雅尔津斯基等式在聚合物/金属相互作用领域的适用性。此外，SFA和AFM的比较展示了如何基于单分子相互作用来预测宏观相互作用能，为潜在预测新型胶水或涂层的粘附性能以及生物和湿粘附提供了一种新策略。
