Paper BI-WeM13
Scaling from Single Molecule to Macroscopic Adhesion at Polymer/Metal Interfaces

Wednesday, October 21, 2015, 12:00 pm, Room 211D

Understanding the evolution of macroscopic adhesion based on the fundamental molecular interactions is crucial to design strong and smart polymer/metal interfaces, which play an important role in many industrial and bio-medical applications. Here we show how macroscopic adhesion can be predicted based on 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 state of an amine/gold junction. Further we use Jarzynski’s equality to obtain the equilibrium ground state energy difference of the amine/gold bond from these non-equilibrium force measurements. In addition, we perform Surface Forces Apparatus (SFA) experiments to measure macroscopic adhesion forces at contacts where approximately 10⁷ 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_BT, which is in excellent agreement with the interaction free energy of 35 ± 3 k_BT 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 based on single molecular interactions, providing a new strategy to potentially predict adhesive properties of novel glues or coatings as well as bio- and wet adhesion.