Nanocomposites silica nanoparticles

Highly disperse silica is widely used in pharmaceutical formulations as a filler, adsorbent, thickener etc.5 Their high hydrophilicity and the absence of emulsifying ability restrict their application. In contrast to hydroxylated silica, partially or fully hydrophobized silica may exhibit improved properties as a drug carrier. The main goal of this work is to study hydrophobized silica nanocomposites with immobilized vitamins C and E. Investigations of adsorption-desorption processes which involve silica nanoparticles and the antioxidants are described. Factors affecting the antioxidant stability have also been carefully considered. 

Lately, we have deposited silver nanoparticles with an average size of 5 nm on the surface of preformed silica submicrospheres with the aid of power ultrasound [51]. Ultrasound irradiation of a slurry of silica submicrospheres, silver nitrate, and ammonia in an aqueous medium for 90 min under an atmosphere of argon to hydrogen (95 5) yielded a silver-silica nanocomposite. By controlling the atmospheric and reaction conditions, we could achieve the deposition of metallic silver on the surface of the silica spheres. Figure 6.3 depicts a silica-coated sphere. 

The wide assortment of polymer systans (polypropylene, poly(methyl methacrylate) [PMMA], polyepoxide, polystyrol, PC, etc.) is used as a polymeric matrix for nanocomposites production (Ray and Okamoto 2003). The most well-known fillers of polymeric matrix are nanoparticles (silica, metal, and other organic and inorganic particles), layered materials (graphite, layered aluminosilicates, and other layered minerals), and fibrous materials (nanofibers and nanotubes) (Thostenson et al. 2005). Nanocomposite polymer materials containing metal or metal oxide particles attract growing interest due to their specific combination of physical and electric properties (Rozenberg and Tenne 2008, Zezin et al. 2010). Nanocomposites on the base of layered materials... 

Fig. 10 TEM images (scale bars. 100 nm) of (a) PMMA latex armored with Ludox silica nanoparticles. Multilayered nanocomposite polymer colloids with (b) a hairy outer layer of polyacrylonitrile, and (c) a soft shell of poly(n-butyl acrylate). Reproduced from [66] with permission of American Chemical Society...

Disulfide PEGDA Polymer silica nanocomposite Gold nanoparticles, CMHA-S, gelatin-DTPH... 

Mo T-C, Wang H-W, Chen S-Y, Dong R-X, Kuo C-H, Yeh Y-C (2007) Synthesis and characterization of polyimide-silica nanocomposites using novel fluorine-modified silica nanoparticles. J Appl Polym Sci 104(2) 882-8W... 

Liu Y-L, Hsu C-Y, Hsu K-Y (2005) Poly(methylmethacrylate)-silica nanocomposites films from surface-functionalized silica nanoparticles. Polymer 46(6) 1851-1856... 

M. loubert, C. Delaite, E. Bourgeat-Lami, P. Dumas, Synthesis of poly(epsilon-caprolactone)-silica nanocomposites from hairy colloids to core-shell nanoparticles. New J. Chem. 2005, 29,1601-1609. 

These findings suggest that the nanocomposite reaction of Rp—(DOBAA) —Rp oligomer with silica nanoparticles should proceed smoothly under alkaline conditions to afford not only the expected Rp—(DOBAA) —Rp/silica nanocomposite but also ammonium hexafluorosilicate as shown in the plausible reaction mechanism (see Scheme 4.6) [46],... 

Considerable attention has also been paid in recent years to hybrid polymer-silica nanocomposites prepared mostly via a sol-gel process [219,243-254] where 10-100 nm size 3D silica domains (clusters) were covalently bound to the polymer. Polymers deprived of groups reactive in the sol-gel process but prone to hydrogen bonding with silanols of silica nanoparticles have also been successfully incorporated into nanophase-separated hybrid materials [246,248-252]. Some polymer-silica nanocomposites, in particular silica core-polymer shell nanoparticles [255-258], were prepared using 3D fumed silica nanoparticles. 

Sol-gel synthesis presents a soft route to materials preparation, where a sol is obtained from the hydrolysis and condensation of a precursor which can form a gel before subsequent drying and heat treatment allows for conversion to a desired phase. An example of a modified sol-gel approach is the preparation of an iron oxide-silica nanocomposite. Here, the iron alkoxide precursor [Fe(OBu )2(THF)]2 has been hydrolysed using millipore water under ultrasonic irradiation in the presence of tetraethylorthosilicate (TEOS) to afford a nanocomposite comprised of silica and y-Fe203 nanoparticles in a single step. The concentration of TEOS added also affects the particle shape, with roughly spherical particles formed with lower and nanorods at higher concentrations, respectively. 

Later, Goren et al. (2010) eonducted a more systanatic study on the size effect using nanoparticles with the same base geometrical shape (spherical). They prepared PMMA silica nanocomposite foams using two nanosilica of different sizes... 

Yang, J., Han, C.-R., Duan, J.-F., Xu, F., Sun, R.-C., 2013c. Interaction of silica nanoparticle/ polymer nanocomposite cluster network structure revisiting the reinforcement mechanism. Journal of Physical Chemistry C 117, 8223—8230. 

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