Facile preparation of SiO2 hybrid nanoparticles via Cu2+-amine redox-initiated radical polymerization

The CuSO4-catalyzed surface-initiated conventional radical graft polymerization of electron-deficient monomers such as N,N-dimethylacryamide (DMAAm) was carried out from amino-functionalized SiO2 nanoparticles (SiO2–NH2) to directly prepare hybrid SiO2 nanoparticles (SiNPs) chemically grafted with functional poly(N,N-dimethylacryamide) (SiO2-g-PDMAAm) in aqueous media with trimethyltetradecylammonium chloride (TTAC) added as a surfactant. The optimum reaction conditions were as follows: weight feed ratio CuSO4·5H2O:DMAAm:H2O:SiO2–NH2:TTAC of 1:500:5,000:1,000:100 and reaction temperature at 80 °C. Spectroscopy and microscopy confirmed the successful graft polymerization and the formation of hybrid SiNPs with PDMAAm chains. Thermogravimetric analysis indicated the grafting yield could be up to 15.39 wt%. As the active radicals only formed on the SiNP surfaces, there was no free polymer in the reacting mixture. Because of the presence of PDMMAm chains, the hybrid SiO2-g-PDMAAm nanoparticles exhibited an enhanced dispersion stability in aqueous media over the pristine SiO2–NH2, and a thermoresponsive settlement behavior. The parallel experiments with other electron-deficient monomers suggest that the current strategy requires less post-treatment, mild conditions and affords universal applicability.