Probing the Metal Oxide/Polymer Molecular Hybrid Interfaces with Nanoscale Resolution Using AFM-IR

Obtaining chemical information from the buried interface of an organic coating is not straightforward. In this paper, for the first time, atomic force microscopy-based infrared spectroscopy (AFM-IR) is used to probe the chemical interactions at the metal oxide/polymer interface. AFM-IR is a novel technique that provides chemical spectra with spatial resolution below the optical diffraction limits. Poly(acrylic acid) (PAA) on aluminum oxide was chosen as a model system. Two different approaches were used: a thin-layer approach and a cross-section approach. The thin layer confirmed the validity of the AFM-IR to look at the buried interface by comparison with results from the literature. Additionally, with a line scan, the exposed interfaces obtained from cross sections of thick coatings on aluminum substrates were analyzed. A semiquantitative analysis of the spectra from the line scan allowed to identify the chemical contribution coming from the polymer/metal oxide interfaces.