Hydrophobization of Silicon Dioxide Microspheres With Resin Acids of Natural Gums

Abstract

Currently, hydrophobic materials and coatings are of great practical interest due to their unique functional characteristics. The aim of this study was to develop a hydrophobic agent based on SiO2 microspheres hydrophobized with resin acids of natural gums to protect various surfaces. According to quantum chemical modeling, the most energetically advantageous interactions are those of SiO2 with birch gum and pine gum through the COO− group of dihydroabietinic acid (E = −1361.256 kcal/mol), and with cedar gum through COO− group of lambertianic acid (E = −1433.537 kcal/mol). Notably, the most stable “SiO2 – resin acid” molecular complex (η = 0.140 eV) forms when the Si atom interacts with COO− group of dehydroabietinic acid. The synthesized samples are represented by irregularly shaped aggregates consisting of spherical SiO2 microspheres. Two fractions of microspheres with sizes of 50–150 and 400–1000 nm are observed in all the obtained samples. FTIR spectra prove that interaction of SiO2 with resin acids occurs through COO− groups. Samples containing 0.01% and 1% of pine gum as well as all samples containing from 0.05% to 1% of cedar gum have expressed hydrophobic properties, while samples with birch gum, in contrast, have hydrophylic properties.