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Abstract

This work is an attempt to investigate viscosities at the nanometer scale. To do so, the tapping mode atomic force microscopy is used on a triblock copolymer exhibiting a well-defined periodic structure at the nanometer scale. Variations of the oscillator amplitude and phase delay as a function of the tipsample distance are recorded on the glassy and rubbery domains of the copolymer. The experimental data are compared to analytical expressions derived from Stokes law. In the present study, among the different possible expressions of the viscous forces depending on the tip shape and on the experimental length scale, only a force proportional to the indentation depth is able to describe the experimental data. In this particular case, quantitative measurements are possible. Finally, the oscillator is shown to be sensitive to local variations of the viscosity within few nanometers.

Probing viscosity of a polymer melt at the nanometre scale with an oscillating nanotip

“…From an experimental point of view, it should be quite easy to discriminate between these two behaviors [16].…”

Material Anisotropy Revealed by Phase Contrast in Intermittent Contact Atomic Force Microscopy

“…While in-plane elastic anisotropy may play a role, it is not the primary loss mechanism. Measurements of the amplitude and phase as a function of tip-sample displacement may allow us to quantify in-plane stiffness and sliding in the future [23][24][25][26][27].…”

Scanning Probe Microscopy of Complex Polymer Systems: Beyond Imaging their Morphology

“…Dissipation manifests itself as a hysteresis of the force versus displacement curve. Dissipation mechanisms may involve electrical losses, time delays, such as those that happen in viscoelastic materials [13,15,44], or mechanical instabilities due to adhesion [24,45].…”

“…Despite the success of TM-AFM for microstructural characterization, important questions remain about the physical origin of the image contrast [11][12][13][14][15]. The height images are generally considered to display topographic information, but it must be kept in mind that the local mechanical properties of the sample (i.e., the possibility that the tip penetrates the surface slightly) may also contribute to the contrast in the height image.…”

“…This method has two advantages: from an experimental point of view this allows easy identification of hard and soft domains: the strongly phaseshifted parts of the image corresponding to hard domains. From a theoretical point of view, it allows the use of simple approximations providing analytical solutions that help to interpret the experimental data [5,[13][14][15].…”