The energy dissipated between tip and sample during dynamic atomic force microscopy (AFM) is a sensitive measure of local surface properties. We mapped the surface properties of crystalline and amorphous regions in thin films of different kinds of elastomeric polypropylene (ePP) with 10 nm lateral resolution. The dissipated energy as a function of the amplitude setpoint displays discriminative shapes for both polymer regions. Differences in the shape as well as in the maximum amount of dissipated energy are interpreted as different amounts of amorphous material on top of crystalline regions. Indentation experiments at different amplitude setpoints resulted in indentation depths of the AFM tip up to 11 nm, on both crystalline and amorphous regions. This and the change of dissipated energy upon wet chemical etching indicate that crystalline regions are covered by an up to 10 nm thick amorphous layer.

We observe unexpected locally auxetic behavior in elastomeric polypropylene, a semicrystalline polymer with a natural microstructure and a low degree of crystallinity. Our series of scanning force microscopy images show the nanomechanical deformation processes that occur upon stretching a thin film of elastomeric polypropylene. Upon uniaxial stretching, the angle between epitaxially grown lamella branches remains constant and the lamellae elongate, resulting in locally auxetic behavior (negative Poisson's ratio) on the 100-nanometer scale. This mechanism causing auxetic behavior, which was previously proposed on the basis of geometric arguments, appears to be an intrinsic property of certain semicrystalline polymers.

A detailed model for the three-dimensional growth of a screw dislocation and a γ-branching of a lamella of elastomeric polypropylene (ePP) is proposed. The crystallization of a thin film was followed with in situ scanning force microscopy (SFM). Nucleation and growth of individual defects were observed with high temporal and spatial resolution. To identify the three-dimensional volume structure, the defects were examined with nanotomography, which is a layer-by-layer imaging technique based on SFM.

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