Load dependence and scanning size effect on friction of Polytert-butylacrylate film

The friction of Polytert-butylacrylate (P tBuA) film was measured at different temperatures by the friction force microscopy (FFM). The load dependence and the scanning size effect on the friction of the film were investigated. It was found that, because the Young modulus of polymer decreased drastically with the temperature, the friction showed almost linear feature with the external load at temperatures below the glass-to-rubber transition temperature ( T g) of the polymer but sub-linear feature at temperatures above T g. The friction was also observed to increase with the scanning size from 30 to 300 nm but saturate for the larger scanning size. As a comparison, the silicon oxidation films were scanned respectively with a clean tip as well as a polymer coated tip. The results indicated that the behaviour of the scanning size effect on the friction was contributed to the stretch and the fracture of molecular chains as the tip scanning on the polymer film surface.