Identification of Polymeric Colloidal Particles and Their Morphology Using Photo-Induced Force Microscopy

The composition of polymeric colloidal particle mixtures made from polyacrylates and polyurethanes can be determined at the single nanoparticle level in their solid state using infrared (IR) based Photo-induced Force Microscopy (PiFM). The morphological differences between (1) a blend of two individual polymer dispersions and (2) a hybrid dispersion created by incorporating polyacrylate phases during the preparation of polyurethane particles can be clearly elucidated by detecting the photo-induced force responses originating from materials under irradiation of a tunable IR laser at a wavelength at which one of the polymers shows a strong characteristic IR absorption peak. The hybrid dispersion shows a high degree of mixing between the two chemically distinct species, which would otherwise phase separate in a physical blend. PiFM, with its excellent spatial resolution down to the nanometer scale and spectroscopic similarity to the FT-IR technique, shows strong potential in materials characterization for research areas such as colloids in water-based coatings and micro/nano-plastics.