Physical interpretations of multimodal AFM contrast on polymeric materials

In this work we compare and quantitatively analyze eight AFM measurables that can generate materials contrast on soft matter. These include (i) sliding friction force in contact mode; (ii, iii) adhesion and contact stiffness in force-distance curve mapping (both slow and fast variants, e.g. "force volume" and "peak force" modes), (iv, v) phase imaging in net attractive and net repulsive regime dynamic/AC mode (aka traditional amplitude-modulation "tapping mode"); (vi, vii) contact resonance amplitude and frequency under pulsed-IR excitation (aka resonance-enhanced mode on a Bruker NanoIR3 AFM-IR system); (viii) Fourier-reconstructed conservative and dissipative force versus distance relationships cluster-analyzed (with machine learning) and mapped in intermodulation mode (i.e., using an IntermodulationProducts AB Multi Lockin Analyzer / software system). We apply to a model heterogeneous polymeric film of interest to the paint/coating industry, including phase segregation down to the sub-100 nm spatial scale. Complementarity of information (mechanical, tribological, surface energy, chemical) is of strong interest.