Nanospheres emulsion polymerization

Perhaps the most common particle type used for bioapplications is the polymeric microsphere or nanosphere, which consists basically of a spherical, nonporous, hard particle made up of long, entwined linear or crosslinked polymers. Creation of these particles typically involves an emulsion polymerization process that uses vinyl monomers, sometimes in the presence of... 

Figure 6.4 The preparation of nanostructured materials in solution evolves from (a) the classic examples of suspension, dispersion, or emulsion polymerization, to the methods that include the covalent crosslinking of select domains within supramolecular polymer assemblies (b) core crosslinking of polymer micelles (c) shell crosslinking of polymer micelles (SCKs) (d) nanocages from core-eroded SCKs (e) shaved hollow nanospheres from outer shell/core-eroded vesicles.

Polymer nanoparticles including nanospheres and nanocapsules (Fig. 1) can be prepared according to numerous methods that have been developed over the last 30 years. The development of these methods occurred in several steps. Historically, the first nanoparticles proposed as carriers for therapeutic applications were made of gelatin and cross-linked albumin. Then, to avoid the use of proteins that may stimulate the immune system and to limit the toxicity of the cross-linking agents, nanoparticles made from synthetic polymers were developed. At first, the nanoparticles were made by emulsion polymerization of acrylamide and by dispersion polymerization of methylmethacry-late.f These nanoparticles were proposed as adjuvants for vaccines. However, since they were made of non-biodegradable polymers, these nanoparticles were rapidly substituted by particles made of biodegradable... 

The poly(alkylcyanoacrylate) nanospheres, widely used as drug carriers, are prepared by emulsion polymerization according to a method initially introduced by Couvreur et al. The monomers (isobutylcyano-acrylate, isohexylcyanoacrylate, n-butylcyanoacrylate) are dispersed in a continuous acidified aqueous phase under magnetic agitation. The anionic polymerization... 

These monomers were also used to make nanospheres by emulsion polymerization for drug delivery... 

To make nanoparticles able to escape complement activation, Passirani et alJ" proposed to coat nanospheres with heparin. This compound, which is a polysaccharide, is a physiological inhibitor of complement activation in vivo. Heparin-coated poly(methylmetha-crylate) nanoparticles were prepared by emulsion polymerization. In the method, the radical polymerization of methylmethacrylate was initiated by heparin according to an original method involving cerium ions and allowing heparin to covalently attach to poly(methyl-methacrylate). 

Titanium oxide/polystyrene core-shell nanospheres have been prepared using a combined sol-gel/microwave-assisted emulsion polymerization procedure using a modified domestic oven. The sol-gel process gave stable Ti02 colloids that were used as seeds for the subsequent polymerization step accomplished in 1.5 h at 70 °C. 

A sensitive mediatorless sensor of H2O2. Gold electrode was immersed in thiol-functionalized poly(styrene-co-acrylic acid) (St-co-AA) nanosphere latex prepared by emulsifier-free emulsion polymerization of St with AA and functionalized with dithioglycol to assemble the nanospheres. Then, GNPs were chemisorbed onto the thiol groups and formed monolayers on the surface of poly(St-co-AA) nanospheres. Finally, horseradish peroxidase was immobilized on the surface of the GNPs Polymer terminated by 2-(2,4-... 

PACA nanospheres are prepared by emulsion/polymerization in which droplets of water-insoluble monomers are emulsified in an aqueous phase (Couvreur et al., 1979 Couvreur et al, 1982). The mechanism of the polymerization is an anionic process initiated by covalent bases present in the polymerization medium (i.g. OH-ions deriving from water dissociation), as already previously discussed. The reaction takes place in micelles after diffusion of monomer molecules through the water phase. The pH of the medium determines both the polymerization rate and the adsorption of drugs when the latter is ionizable (Couvreur et al, 1979). Drug can be combined wdth nanoparticles after dissolution in the polymerization medium either before the introduction of the monomer or after its polymerization. The size of the nanospheres obtained is approximately 200 nm, but it can be reduced to 30-40 nm using a non ionic surfactant in the polymerization medium (Seijo et al, 1990) or by adding SO9 to the monomer (Lenaerts et al, 1989). 

Xu, H. et al (2006) Development of high magnetization Fe304/polystyrene/silica nanospheres via combined miniemulsion/ emulsion polymerization. /. Am. Chem. Soc., 128 (49), 15582-15583. 

Xu H, Cui L, Tong N, Gu H. Development of high magnetization FCjO polystyrene/silica nanospheres via combined miniemulsion/emulsion polymerization. J Am Chem Soc 2006 128(49) 15582-3. 

Fig. 11 Preparation of hollow polymeric nanospheres via water-oil-water emulsion polymtaization...

The method for preparing biodegradable poly(alkylcyanoacr 4ate) nanospheres has provided the basis for the development of polycyanoacrylate nanocapsules. Al Khouri-Fallouh et al (1986) proposed an original method in which the monomer is solubilized in an alcohol phase containing an oil and is then dispersed in an aqueous phase containing surfactants. In contact with water, the alcohol phase diffuses and favours the formation of aver fine oil-in-water emulsion. The monomer, insoluble in water, polymerizes at the interface of the phases to form the wall of the nanocapsules. 

Heterogeneous polymerization Precipitation Emulsion Dispersion PNIPAM microgel nanoparticles Poly(PNIPAM-co-AA) microgel nanoparticles NPs based on poly(butyl methacrylate) core and PNIPAM shell Colloidal nanospheres of poly(butylcyanoacrylate) with a magnetite core Pegylated NPs composed of N,N- diethylacrylamide and N,N-methylene bisacrylamide Berndt et al., 2006 Jones and Lyon, 2000 Gan and Lyon, 2003 Arias et al., 2008 Rieger et al., 2009... 

Polymeric carbons can be prepared in different shapes. As shown in Figure 7.26, carbon nanospheres (CNS) with an average diameter of about 50 nm can be prepared by emulsion reaction, coating, heat treatment, and washing. If there is no coating process, the PAN nanoparticles will aggregate and cross-link during the heat-treatment [15]. The prepared CNS has a unique nanostructure and potentially can achieve excellent rate capability [15]. 

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