Polymer nano-adhesion between a cantilever tip coated with polymer and a flat polymer film was studied by a light-lever system using an atomic force microscope. The polymer interface was adhered at a temperature above the surface glass transition temperature for a given time. Nano-adhesion force (F nano), at which the tip was detached from the surface, was estimated from the deflection of the lever with a known spring constant. Nano-adhesion strength (GN) was simply obtained dividing Fnano by the contact area, which was estimated on the basis of Johnson-Kendall-Roberts theory. The time evolution of the interfacial thickness was independently examined by dynamic secondary ion mass spectrometry. Interestingly, G N increased with increasing interfacial thickness. However, it can be hardly judged whether GN is proportional to the interfacial thickness with the exponent of 1 or 2. Then, temperature dependence of G N was examined. Above the bulk glass transition temperature, the relation between temperature and GN was well expressed by a Williams-Landel-Ferry type equation. This means that the nano-adhesion strength is governed by friction between segments. Once this is accepted, GN should be proportional to the interfacial thickness with the exponent of 2.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy(all)