Surface hydrophobization of magnetite nanoparticles with polyhexylsilsesquioxane in diethylamine as reaction solvent

A facile method for surface hydrophobization of magnetite (Fe3O4) nanoparticles with polyhexylsilsesquioxane was proposed. The surface-hydrophobizing coating formed of polyhexylsilsesquioxane on the surface of the magnetite nanoparticles was spontaneously generated from hexylated silanol moiety dissolved in diethylamine. Due to the Lewis basicity, diethylamine worked as the catalyst for the polycondensation of the hexylated silanol, At the same time, the relatively low polarity of diethylamine was found favorable for maintaining the dispersibility of the polyhexylsilsesquioxane-coated magnetite nanoparticles. Moreover, the presence of the surface-hydrophobizing coating was effective for suppressing the transition of the magnetite phase to hematite (alpha-Fe2O3) even under highly oxidative condition since the polyhexylsilsesquioxane coating blocked oxygen molecules from the access to the surface of the magnetite nanoparticles as evidenced by the absence of micropores in the polyhexylsilsesquioxane coating layer. (C) 2016 Elsevier B.V. All rights reserved.