Function and performance of silicone copolymers, 5. Syntheses and surface characterization of an acrylized silica monomer

Silica surfaces have been reacted with 2-hydroxyethyl methacrylate (2-HEMA) to prepare acrylized silica monomer (SM). The chemical structure and chemical composition of this new monomer have been extensively characterized by FTIR, solid-state NMR, XPS, and elemental analysis (EA). The appearance of C=C and C=O peaks in the IR adsorption spectra from SM, the shift of the ¹³C NMR peak of the ethylene group carbon of the 2-HEMA moiety in SM and the higher carbon content on the surface of the modified silica particle (XPS analysis) compared to the entire silica particles (elemental analysis) give evidence that 2-HEMA has been successfully reacted onto the silica surface. The SM was copolymerized with stearyl acrylate (SA) to obtain a series of copolymers (PSS) whose chemical structures have been characterized by FTIR and solid-state NMR. Thermogravimetric analysis (TGA) has been used to study the thermal stability of these copolymers, and it was found that the addition of SM was very effective in improving the thermal stability. The carbon content of SM and PSS were used to calculate the fraction of silanol groups reacted with HEMA, the HEMA concentration on the surface of silica, and the mole ratio of SA/SM in PSS. Those results were used to calculate the theoretical amount of residual material at 700°C (R₇₀₀′). It was found that the theoretical values of R₇₀₀′ are very close those obtained from the TGA experiment (R₇₀₀′).