A number of new silica fillers have been obtained in the emulsion system and changes in their surface properties appearing as a result of modification with the following alkoxysilanes have been evaluated: [3-(phenylamino)propyl]trimethoxysilane (PhAPS), (3-glycidoxypropyl)trimethoxysilane (GPS), N-2-(aminoethyl)-3-aminopropyltrimethoxysilane (AEAPS), 3-mercaptopropyltrimethoxysilane (McPS) and octyltriethoxysilane (OS). Functionalization Of SiO2 surface has been made with different amounts of the modifiers. The fillers have been characterized by determination of their dispersion, adsorption abilities, morphological and chemical properties (effectiveness of modification and hydrophobization determined by wetting and sedimentation methods). The silica-based fillers obtained have been made of spherical shaped particles characterized by high size uniformity (low polydispersity index) of the mean diameter within the range 440-520 not. The fillers show limited hydrophilic properties as confirmed by the wettability and sedimentation tests in water. (C) Koninklijke Brill NV, Leiden, 2009