Surface properties of calcium and magnesium oxide nanopowders grafted with unsaturated carboxylic acids studied with inverse gas chromatography

Inverse gas chromatography (IGC) was applied at infinite dilution to evaluate the surface properties of calcium and magnesium oxide nanoparticles and the effect of surface grafted unsaturated carboxylic acid on the nanopowder donor–acceptor characteristics. The dispersive components (γsD) of the free energy of the nanopowders were determined by Grayʹs method, whereas their tendency to undergo specific interactions was estimated based on the electron donor–acceptor approach presented by Papirer. The calcium and magnesium oxide nanoparticles exhibited high surface energies (79 mJ/m2 and 74 mJ/m2, respectively). Modification of nanopowders with unsaturated carboxylic acids decreased their specific adsorption energy. The lowest value of γsD was determined for nanopowders grafted with undecylenic acid, approximately 55 mJ/m2. The specific interactions were characterised by the molar free energy (ΔGASP) and molar enthalpy (ΔHASP) of adsorption as well as the donor and acceptor interaction parameters (KA, KD).