Nano precursor of aluminum hydroxide was synthesizes by direct precipitation from aluminum nitrate and sodium hydroxide in the presence of polyethylene glycol. Al2O3 nanoparticles (AON) were prepared by calcinations of the precursor at 850 degrees C for 10 h. Aluminum oxide nanoparticles with average diameter of about (23 nm) were modified with oleic acid (OA-AON) as coupling agent. Successful surface modification of nanoparticles allows them to form stable dispersions and prevents aggregation of the nanoparticles. Then dispersibility of surface modified nanoparticles was examined in some monomers with different levels of hydrophobicity, including methylmetacrylate (MMA) butylacrylate (BuA) and Styrene (ST) having low, medium high hydrophobicity, respectively. To examine their dispensability, aluminum oxide were dispersed in mentined monomers, then Al2O3 loaded monomers were allowed to stand at room temperature for 24 h and the precipitate part of nanoparticles was separated and the amount of stable particles in dispersion was determined. The morphology and structures of nanoparticles were characterized by FT-IR, UV/VIS, X-ray diffraction (XRD) and scanning electron microscopy (SEM). These characterizations confirmed grafting of coupling agent on the surface of aluminum oxide nanoparticles, and showed that the surface modification of nanoparticles has been carried out successfully, so that their surface is rendered more hydrophobic.

Keywords: Aluminum oxide; Oleic acide; Surface modification; Dispersion