The morphology and topography of polymer surfaces and interfaces exposed by ultra-low-angle microtomy

Abstract

The ultra-low-angle microtomy (ULAM) technique has been developed to impart a cross-sectional, ultra-low-angle taper through polymeric materials such as coatings and paints. ULAM employs a conventional rotary microtome in combination with high-precision, angled sectioning blocks to fabricate the ultra-low-angle tapers. Subsequent investigation of the tapers produced by ULAM may be used in conjunction with X-ray photoelectron spectroscopy (XPS) or time-of-flight secondary ion mass spectrometry (ToF-SIMS), for compositional depth profiling or ‘buried’ interface analysis. Variation in the selection of the ULAM taper angle and/or the analysis interval size employed enables depth resolution at the nanometre or micrometre scales to be achieved. In the work described here scanning electron microscopy (SEM) and atomic force microscopy (AFM) have been employed to investigate the morphology and topography of the surfaces resulting from the ULAM tapering process. It is demonstrated that a correctly mounted polymeric sample, sectioned with a sharp microtome knife, displays little perturbation of the resulting polymeric surface after ULAM processing. Additionally, SEM analysis of the interface region between a poly(vinylidene fluoride) (PVdF) topcoat and polyurethane (PU) primer exposed by ULAM processing reveals that the interface region between the two coatings possesses a well-defined boundary. No evidence of polymeric smearing across the interface is observed. XPS compositional depth profiling across a ‘buried’ PVdF/PU interface, exposed by ULAM processing, is employed to demonstrate the utility of the ULAM technique.

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