Bulk concentration effects on the structure and orientation of adsorbed silane on the surface of nanosized SiO₂ particles

In this study, the concentration effects of 3- methacryloxypropyltrimethoxysilane (MEMO) on the surface coverage extent, orientation, and structures of MEMO silane grafted onto the surface of SiO ₂ particles are investigated using Fourier transform infrared (FTIR) and ²⁹Si-NMR spectroscopy. The MEMO silane concentration effects on the rheological behaviors of the SiO₂ particles-1,6- hexanedioldiacrylate (HDDA) suspensions are discussed in terms of the surface coverage extent and the MEMO silane structures grafted onto the surface of SiO₂ particles. At low MEMO concentrations, many free silanol SiOH groups were observed for the MEMO grafted onto the SiO₂ surface and the adsorbed MEMO molecules tended to orient parallel to the SiO₂ surface due to the hydrogen bonding of the MEMO-carbonyl and the hydroxyl group of the oxides. At high MEMO concentrations, the condensation reactions between neighboring grafted MEMO molecules result in the predominance of a T² and T³ silicon atom structure and complete coverage of the SiO ₂ surface by the grafted MEMO. The enhanced steric hindrance and compatibility between the MEMO-modified SiO₂ particles and HDDA monomer, which originate from the complete coverage of the SiO₂ surface by MEMO silane and a higher proportion of free carbonyl groups on the grafted MEMO, may improve the dispersibility of nanosized SiO₂ in acrylate suspensions.