Calcium Sulfate Nanoparticles with Unusual Dispersibility in Organic Solvents for Transparent Film Processing

• Published in: Langmuir Vol. 34; no. 24; pp. 7096 - 7105
• Main Authors: Leukel, Sebastian, Panthöfer, Martin, Mondeshki, Mihail, Schärtl, Wolfgang, Plana-Ruiz, Sergi, Tremel, Wolfgang
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 19-06-2018
• ISSN: 0743-7463; 1520-5827
• DOI: 10.1021/acs.langmuir.8b00927

Calcium sulfate is one of the most important construction materials. Today it is employed as high-performance compound in medical applications and cement mixtures. We report a synthesis for calcium sulfate nanoparticles with outstanding dispersibility properties in organic solvents without further functionalization. The nanoparticles (amorphous with small γ-anhydrite crystallites, 5–50 nm particle size) form long-term stable dispersions in acetone without any sign of precipitation. 1H NMR spectroscopic techniques and Fourier-transform infrared spectroscopy (FTIR) reveal absorbed 2-propanol on the particle surfaces that induce the unusual dispersibility. Adding water to the nanoparticle dispersion leads to immediate precipitation. A phase transformation to gypsum via bassanite was monitored by an in situ kinetic FT-IR spectroscopic study and transmission electron microscopy (TEM). The dispersibility in a volatile organic solvent and the crystallization upon contact with water open a broad field of applications for the CaSO4 nanoparticles, e.g., as nanogypsum for coatings or the fabrication of hybrid composites.