Preparation of PEG-grafted silica particles using emulsion method

Low-molecular-weight poly(ethylene glycol) (PEG) was grafted onto the surface of silica particles by a two-step addition process. To prepare PEG-grafted silica particles, PEGME-IPTES monomers were synthesized by the reaction of 3-(triethoxysilyl)propyl isocyanate (IPTES) with poly(ethylene glycol) methyl ether (PEGME) in the presence of dibutyltin dilaurate. To remove PEGME residues, excessive IPTES was added to the solution. The peak for a urethane carbonyl group of PEGME-IPTES was observed at 1722 cm−1 by FT-IR spectroscopy. Through the sequential addition of TEOS and PEGME-IPTES monomers, PEG was introduced onto the surface of silica particles. The introduction of PEG onto the surface was observed by SEM, Brunauer-Emmett-Teller (BET), and FT-IR spectroscopy. When PEG was grafted onto the surface of silica particles, the surface area of silica particles decreased and the average pore diameter increased. The peak for urethane carbonyl group and alkyl group of PEG appeared at 1722 cm−1 and 2920 cm−1.