AdaptiveS

Atomic force microscopy is an imaging technique in which a very fine tip (tip radius down to 10 nm) scans over the sample surface. Information about the topography of the samples can be obtained from the interaction between the sample surface and the tip. The atomic force microscope at IVW (Bruker Dimension IconIR) also features other integrated measurement modes that can be used to capture and map not only the topography but also other surface properties at the nanoscale.

These measurement modes are:

- Peak Force QNM for nanomechanical properties (deformation, DMT modulus, pull-off force, dissipation)

- Nano-DMA for viscoelastic properties (storage modulus, loss modulus, loss factor)

- AFM-IR for nanoscale resolving IR spectroscopy in the wave number range of 1800-750 cm^-1

- Nano-TA for nanoscale thermal analysis in the range of 20 - 350 °C

In Peak Force QNM experiments, the indentation force is kept constant (typically 100-300 nN) and the topography is measured as a function of the interaction between the tip and the sample surface. The DMT modulus, pull-off force, deformation and dissipation are determined pixel by pixel. Figure 1 shows the results of such a mapping on epoxy resin containing block copolymers as a second phase.

It is assumed that the block copolymer is present in the form of spherical inclusions. It exhibits a lower DMT modulus, higher pull-off force, deformation and dissipation than the epoxy resin. Definitive proof is provided by AFM-IR spectroscopy at the same location on the sample (Fig. 2). In addition to the topography, the absorption of the C=C stretching vibration (1640 cm^-1, green coloring) characteristic of the block copolymer is also measured. The IR examination in the AFM clearly shows the dominant presence of the block copolymer in the spherical areas.