When two objects are in contact, the force necessary for one to start sliding over the other is larger than the force necessary to keep the sliding motion going. This difference between static and dynamic friction is thought to result from a reduction in the area of real contact upon the onset of slip. Here, we resolve the structure in the area of contact on the molecular scale by means of environment-sensitive molecular rotors using (super-resolution) fluorescence microscopy and fluorescence lifetime imaging. We demonstrate that the macroscopic friction force is not only controlled by the area of real contact but also controlled by the "quality" of that area of real contact, which determines the friction per unit contact area. We show that the latter is affected by the local density of the contacting surfaces, a parameter that can be expected to change in time at any interface that involves glassy, amorphous materials.

Additional Metadata
Keywords General Materials Science
Publisher ACS
Funder NWO
Persistent URL dx.doi.org/10.1021/acsami.9b19125
Journal ACS Appl. Mater. Interfaces
Petrova, D, Sharma, D.K, Vacha, M, Bonn, D, Brouwer, A.M, & Weber, B. (2020). Ageing of Polymer Frictional Interfaces: The Role of Quantity and Quality of Contact. ACS Appl. Mater. Interfaces, 12(8), 9890–9895. doi:10.1021/acsami.9b19125