E. Boschung et al., ENERGY-DISSIPATION DURING NANOSCALE INDENTATION OF POLYMERS WITH AN ATOMIC-FORCE MICROSCOPE, Applied physics letters, 64(26), 1994, pp. 3566-3568
Nanometer size indentations on polypropylene and polymethylmethacrylat
e were made with the atomic force microscope and were 200-nm wide and
20-nm deep for a tip penetration depth of 75 nm. To image the indentat
ions with the same tip used for writing, the tip was retracted at high
speed, thus detaching any polymer sticking on it. Nanomechanical prop
erties of polymer are studied in the limit of shallow indentations and
slow penetration speed. From the hysteresis of the force versus tip m
otion curve, the dissipated energy during the indentation and the inel
astic deformation of the polymer surface can be measured. We find that
the measured dissipated energy is proportional to the volume of the i
ndentation times the activation energy needed to excite chain segments
motion during the deformation.