Force Mapping of Polymer Blends

A 3 1 solution of P2VP (Mw = ca. 300,000 g/mol) and PtBMA (Mw = ca. 850,000 g/mol) in THF is spincoated on pre-cleaned silicon substrates at 3,000 rpm for 1 min followed by drying in vacuum. The silicon sample is attached to the sample disc using pressure sensitive adhesive. 

For pulsed force mode imaging, a stiff contact mode lever (kN 0.6 N/m) is selected. A modulation frequency in the range of 800 Hz is selected and the cantilever oscillations are adjusted such that the adhesive interactions between tip and surface are overcome, as monitored using an oscilloscope. The modulation must clearly show the snap-off of the tip. Next the four markers are set according to the general procedure outlined in Sect. 3.2 in Chap. 3. 

Pulsed force mode scans on the thin film of the phase separated blend of P2VP and PtBMA show pronounced contrast in two imaging modes, i.e., height and adhesion, while the stiffness suffers to some extent from artefacts. In a new mode called combined dynamic X mode SFM, these problems are overcome [30]. 

4 Polymer Surface and Interface Properties and (Dynamic) Processes 

The measurement of friction forces, in particular on multicomponent systems, may provide a rapid, qualitative insight into the distribution of the components and may be useful to map local functional group distributions. For quantitative friction mode AFM work, calibration procedures for the lateral spring constant and the AFM detection system become crucial. These calibration approaches are more demanding than the one described in Sect. 4.1, but because of recent progress in calibration standard development can be successfully tackled. 

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