Effects of static and dynamic forces on surface viscoelastic response of polymer films in scanning viscoelasticity microscopy

Scanning force microscopy with force-modulation mode enables one to gain direct insights into local viscoelastic properties at polymer surfaces. Changing modulation condition such as dynamic amplitude and frequency in addition to static normal force, surface viscoelastic response of polystyrene (PS) film was studied. If dynamic and/or static forces were/was ill-chosen, non-linearity of viscoelastic response became dominant, resulting in hole formation at the surface. On the contrary, if they were appropriately adjusted, linear viscoelastic measurement could be realized in the frequency range from 10 Hz to 4 kHz. This leads to traditional rheological analysis even at the surface.