{
    "protocol": "Silica nanoparticles, of size 10-15 nm, were used in a 30% dispersion in methanol, either directly without modification or modified by polyethylene glycol-modified silane and acrylate/methacrylate-modified silanes.Monomethyl ether polyethylene glycol (mPEG) (Mw=1100) was dissolved in toluene and the mixture was dried. At room temperature and under nitrogen, a molar equivalent (with respect to the mPEG) of 3-isocyantopropyl trimethoxysilane was added dropwise to the reaction mixture. A few drops of dibutyl tin dilaurate were added as a catalyst. The reaction mixture was then stirred continuously for 24h at 50°C. The reaction was monitored by infrared spectroscopy; the isocyanate signal is at 2271cm^-1. Upon completion, approximately two thirds of the toluene was removed by rotary evaporation and the mPEG trimethoxysilane was precipitated into hexane and washed several times. The resulting solid was dried and characterized by 1H NMR. Reaction yields of >90% were obtained.The surface of silica nanoparticles was functionalized with mPEG triethoxysilane and 3-(trimethoxysilyl)propyl acrylate or 3-(trimethoxysilyl)propyl methacrylate. The mixtures were stirred at room temperature overnight to finish the reaction.Formulations were prepared by mixing modified or unmodified silicon oxide nanoparticles with reactive diluents, polyethylene glycol diacrylate (Mw=575 g mol^{-1}), sulfopropyl acrylate potassium salt, and a photoinitiator, 1-hydroxycyclohexyl benzophenone. The sulfopropyl acrylate potassium salt was added as a solution in water. All the liquid coatings have a solid content of about 12%. Coatings were applied on PET or polycarbonate sheets using #16 wire wound rod. The coatings were dried for half a minute, and then cured under a 300 W per inch mercury vapor lamp at a dose of 1 J/cm^2 in a nitrogen atmosphere. The thicknesses of the cured coatings were about 5 micrometers."
}