Preparation, stabilization and characterization of 3-(methacryloyloxy) propyl trimethoxy silane modified colloidal nanosilica particles

In this study, homogeneous distribution of colloidal silica nanoparticles (CSPs) was performed by modifying and stabilizing CSPs in an organic solvent at neutral pH. The surface modified CSPs were synthesized by Stöber method in methanol, followed by modifying with different contents of 3-(methacryloyloxy) propyl trimethoxysilane (MPTS). Solvent exchange and dialysis process were applied to purify the modified CSPs for being stable in dioxane solvent at pH 7 ± 0.1. Both original and modified CSPs exhibited narrow particle size distribution in the range of 10–100 nm, while dynamic diameters (Z-averaged) of the CSPs were not significantly changed after modification and purification process (about 29 nm and 30 nm, respectively). Thermal Gravimetric Analysis (TGA) diagrams, Fourier Transform Infrared (FTIR), Energy Dispersive Spectroscopy (EDS) and Proton Nuclear Magnetic Resonance (¹HNMR) spectra analyses showed the successful grafting of hydrolyzed MPTS on the surface of CSPs, which increased with increasing MPTS loading (0.3, 0.45, 0.6, 1.0, 1.5 g/g of SiO₂). At low MPTS loadings (0.3, 0.45 g/g of SiO₂), the graft amount of MPTS on the surface was not saturated, therefore hydrogen bonds between CO groups of MPTS layer and surface hydroxyl group of CSPs have been occurred, however, these ineractions were disappeared at higher MPTS loadings. Scaning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) images verified the nanoscale distribution of CSPs with 20–30 nm particle size. Based on the above results, monolayer grafting of hydrolyzed MPTS was successfully incorporated on the surface of CSPs leading to be stable in dioxane solvent. Dialysis method using dioxane solvent can be applied for purification of modified CSPs solution, which also preserved the nanoscale distribution of modified CSPs.