Growth of silica nanoparticles in methylmethacrylate-based water-in-oil microemulsions |
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Authors: | S Scholz H Althues S Kaskel |
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Institution: | (1) Department of Inorganic Chemistry, Technical University of Dresden, Mommsenstr. 6, 01069 Dresden, Germany |
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Abstract: | The mechanism of silica particle formation in monomer microemulsions is studied using dynamic light scattering (DLS), atomic
force microscopy, small-angle X-ray scattering (SAXS), and conductivity measurements. The hydrolysis of tetraethylorthosilicate
(TEOS) in methylmethacrylate (MMA) microemulsions (MMA = methylmethacrylate) is compared with the formation of SiO2 particles in heptane microemulsions. Stable microemulsions without cosurfactant were found for MMA, the nonionic surfactant
Marlophen NP10, and aqueous ammonia (0.75 wt%). In the one-phase region of the ternary phase diagram, the water/surfactant
ratio (R
w) could be varied from 6 to 18. The DLS and SAXS measurements show that reverse micelles form in these water-in-oil (w/o)
microemulsions. The minimum water-to-surfactant molar ratio required for micelle formation was determined. Particle formation
is achieved from the base-catalyzed hydrolysis of TEOS. According to atomic force microscopy measurements of particles isolated
from the emulsion, the particle size can be effectively tailored in between 20 and 60 nm by varying R
w from 2–6 in heptane w/o microemulsions. For MMA-based microemulsions, the particle diameter ranges from 25 to 50 nm, but
the polydispersity is higher. Tailoring of the particle size is not achieved with R
w, but adjusting the particle growth period produces particles between 10 and 70 nm. |
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Keywords: | Silica nanoparticles Reverse microemulsions Acrylates Dynamic light scattering Atomic force microscopy |
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