Interfacial phenomena in composites with nanostructured succinic acid bound to hydrophilic and hydrophobic nanosilicas

To improve release of bioactive succinic acid (SA) from various composites, it has to be transformed into a nanocrystalline state. To this aim, the SA powder was added to hydrophilic (A-300) or hydrophobic (AM1) nanosilicas or their blends in dry state or with addition of water and then carefully stirred. The obtained nanocomposites were characterized in depth by low-temperature and solid-state NMR spectroscopies, nitrogen adsorption, TEM, SEM, XRD, FTIR, and quantum chemistry. Despite SA water-solubility, nine-fold excess of water with respect to SA is not enough to dissolve all SA because water bound to nanosilicas is not an active solvent. Moreover, size of SA crystallites bound to nanosilicas can be reduced down to 30 nm, and the final nanocomposites can be stable in air since bound SA can be dissolved only in aqueous media that is of importance for practical applications related to drug carries, adsorption, etc.