Cross-Sectional Chemical Nanoimaging of Composite Polymer Nanoparticles by Infrared Nanospectroscopy

Nanoscale Fourier transform infrared spectroscopy (nano-FTIR) is an emerging technique that allows for label-free chemical nanoimaging. Here, we introduce its application to studying multicomponent nanostructured polymer particles synthesized by emulsion polymerization and demonstrate its excellent sensitivity to local chemical composition via hyperspectral infrared nanoimaging and subsequent chemometric analysis. To that end, we developed a method for preparing thin particle slices without any embedding material, thus avoiding chemical contamination. In particular, we studied particles composed of acrylic and fluoroacrylate monomers. Nano-FTIR reveals an unexpected composition for each of the phases that forms the complex core–shell–shell morphology, which provides unprecedented chemical insights beyond conventional electron microscopy analysis of the same particles. Label-free chemical nanoimaging and infrared nanochemometrics of individual phases inside multicomponent polymer particles will benefit the understanding of particle formation and the development of novel synthesis recipes and strategies.