Modification of silica nanoparticles and their application in UDMA dental polymeric composites

Advancements in nanocomposites are highly dependent on the compatibility between the organic matrix and inorganic fillers, and the dispersion level of fillers throughout the matrix. Silane coupling agents are widely used to change the chemical structure of particles' surface in order to improve their compatibility and dispersion properties of particles. SiO2 nanoparticles were modified by gamma-methacryloxy propyl trimethoxy silane, which provided double bonds to the particle surface. These groups can covalently bond with monomers to form a three-dimensional network within the composites. After the surface modification, the dispersion performance of particles in different media (water, ethanol, acetone) was studied. Infrared spectroscopy and transmission electron microscopy were used to identify the structure of modified SiO2. The dispersion degree and stability properties of modified SiO2 in three media were investigated by the measurements of contact angle, C potential, turbidity, and relative viscosity. The results indicate that the stability and dispersion degree in organic solvents have been improved after the modification. In addition, the mechanical properties of composites with modified silica were also studied, which indicated that, after the pre-dispersion of particles in organic media, the mechanical properties of materials could be improved, even at low filler content.