Controlling hydrophobicity of silica nanocapsules prepared from organosilanes

• Published in: Colloids and surfaces. A, Physicochemical and engineering aspects Physicochemical and engineering aspects, 2017-11, Vol.532, p.172-177
• Main Authors: Hood, Matthew A., Encinas, Noemí, Vollmer, Doris, Graf, Robert, Landfester, Katharina, Muñoz‐Espí, Rafael
• Format: Article
• Language: English
• Subjects: 29Si-NMR; Contact angle; Hydrophobization; Inverse miniemulsion; Silica nanocapsules; Solid–state
• ISSN: 0927-7757; 1873-4359
• DOI: 10.1016/j.colsurfa.2017.05.047

[Display omitted] •Simple method for hydrophobic silica nanocapsules synthesis.•Chlorosilanes are not effective for capsule formation compared to alkoxysilanes.•Solid-state 29Si NMR measurements indicate hydrophic silanes within TEOS network.•DLS showed capsule breakage with time in caustic media.•Contact angle analysis shows hydrophobicity of modified silica nanocapsules. Silica nanocapsules with various degrees of surface hydrophobicity were produced by using the inverse miniemulsion technique. Tetraethylorthosilicate was added concurrently with organosilanes containing a variety of hydrophobic ligands (e.g., cyclohexyl and octadecyl). The method is simple and yields nanosized capsules capable of containing hydrophilic components, while using relatively low amounts of surfactants. Commercially used hydrophobic chlorosilanes were demonstrated to be poor additives for the formation of silica nanocapsules. 29Si solid-state NMR was performed on selected silica nanocapsules to show that hydrophobic alkoxysilanes were incorporated within the silica nanocapsule network. Dynamic light scattering measurements of hydrophobized nanocapsules in a caustic medium indicated a relative increase in size with regard to pure silica nanocapsules. Contact angles of water on the nanocapsules generally increased with the length of hydrophobic ligand suggesting less interaction of the surface with water. The hydrophobicity of the nanocapsules was related to their ability to repulse a caustic water environment, thus delaying silica network degradation, which would cause nanocapsule breakage.