2022 Photography contest winner
Photo: “Perfect combination of Science”. Compatibility between Styrene-Acrylonitrile (SAN) copolymer and Polybutadiene (PB) polymer phases to obtain high performance latexes.

2D-STEM micrograph of a dry acrylonitrile-butadiene-styrene (ABS) latex is observed in the left image. ABS latex with 36 % of solid content was synthetized by seeded semi-batch emulsion polymerization. For the sample preparation, the ABS latex was first dialyzed to remove adsorbed species on the surface of the particles, mainly to avoid staining of the surfactant used during the grafting reaction. Then, the polymer latex was dried on a Transmission Electron Microscopy (TEM) grid and stained with OsO4 for one hour, which selectively reacted with the vinylic bonds of the PB. In HAADF-STEM, the contrast of the image is opposite to common TEM micrographs, which means that the PB matrix phase stained with OsO4 will correspond to the bright area while the SAN phases (shell and clusters) to the dark. The image presents the 2D-STEM tomographic image at position OZ = 124 of the particle, where the OZ axis coincides with the direction of the electron beam, and the OY axis is the tilting axis.