Polymeric powders preparation

Dezanneau et al. reported Lai cMn03+a nanocrystalline powders prepared by an acylamide polymerization sol-gel method (Dezanneau et al., 2002a,b, 2003). The composition analysis revealed that for La/ Mn < 0.9 the Mna04 phase was present, while for La/Mn > 0.9, the high oxygen excess led to considerable vancancies on cationic sites. The Curie temperature remained constant at 295 K for the former case, while decreased Curie temperatures were observed for the latter case, due to the increasing amoimt of Mn vacancies. 

Tservistas, M. Levy, M.S. Lo-Yim, N.Y.A. O Kennedy, R.D. York, R Humphreys, G.O. Hoare, M. The formation of plasmid DNA-loaded pharmaceutical powders using supercritical fluid technology. Biotech. Bioeng. 2001, 71, 12-18. Bodmeier, R. Chen, H. Indomethacin polymeric nanosuspensions prepared by microfluidization. J. Controlled Release 1990, 12, 223-233. 

The following fundamental aspects of the colloid chemistry of silica are briefly reviewed in this chapter nucleation, polymerization, and preparation stability of sols surface structure characterization methods sol-gel science gels and powders and uses of silica sols and powders. Silica in biology is not within the scope of this book. Scientists working in this area should soon put together a protocol covering progress done since the publication of Iler s book. 

Lee, S.J., Kriven W.M. Crystallization and densification of nano-size, amorphous cordierite powder prepared by a solution-polymerization... 

Goetzinger, W., et al.. Characterization of high molecular mass linear polyacrylamide powder prepared by emulsion polymerization as a replaceable polymer matrix for DNA sequencing by capillary electrophoresis. Electrophoresis, 19, 242, 1998. 

Au, Fe, and Cr sols were prepared by the reduction of their hydroxides by hydrazine hydrate in a matrix of water-soluble polymers, and dispersions of particles of Pd (1-2 nm) and Au (1-13 nm) were obtained in synthetic rubber films. Polymeric films prepared from aqueous solutions of PVAl and AgNOs were treated with photographic reducing agents (hydroquinone, p-phenylenediamine, pyrogallol, etc.) to produce die corresponding metallocomposite materials. Monodispersed hyperfine powders of gold and platinum were prepared by the reduction of... 

The basic physical parameters of polymeric matrices prepared by simple physical mixing of drug and polymer powders are reviewed The wettability of the matrix, its pore structure and the permeability of the polymer particles resulted to be the controlling factors in the overall penetration process and in the subsequent drug release mechanism A simple experimental approach to the identification of the penetration mechanism is proposed, which allows to distinguish between a capillary driven penetration and a diffusion controlled permeation process ... 

Active uranium prepared by Na/K reduction in DME is also an extremely active polymerization catalyst and will polymerize 100 equiv of 1,3-butadiene at -4°C and atmospheric pressure in less than Ih. This is much more reactive than the active uranium powder prepared by Chang et al. (via thermal decomposition of U/Hg) which polymerized 80% of 1,3-butadiene (latm) in 4h at 70°C [62]. The resulting polybutadiene prepared by our method exhibited IR bands corresponding to cis (675cm ), vinyl (910cm ), and trans (970cm ) morphologies [63]. 

Garay I., Pocheville A, Madariaga L. (2010). Polymeric microparticles prepared by supercritical antisolvent precipitation. Powder TechnoL, 197,211-217. 

Infrared spectroscopy is predominantly performed in the Fourier-transform mode and then commonly abbreviated as FTIR. The great advantage of FTIR spectroscopy is the great number of measurement options (and accessories), that allow spectra to be taken conveniently from just about any kind of sample. Polymeric powders can be characterized by pressing them into the conventional KBr pellets, but also, without any sample preparation, by diffuse reflectance (DRIFT). Very thin films of polymers can be measured in the conventional transmission mode, but any kind of film (thick or thin), as well as large polymeric objects, can be measured by ATR. ATR probes can also be used to characterize solutions... 

Choi et al. reported the preparation of CdS and polyacrylonitrile (PAN)-CdS nanocomposites by y-irradiation polymerization." The prepared CdS and PAN-CdS nanocomposites were characterized by powder XRD, IR spectroscopy, Fourier transform (FT) Raman spectroscopy, TEM, X-ray photoelectron spectroscopy (XPS) and TGA (thermogravimetric analysis/dynamic thermal analysis). In photoluminescence (PL) spectroscopic analysis, the maximum peak of PAN-CdS nanocomposites prepared by y-irradiation polymerization was at about 485 nm, whereas the maximum peak of CdS nanocomposites was at about 460 nm. 

Suspension Polymerization. Suspension polymerisation yields polymer in the form of tiny beads, which ate primarily used as mol ding powders and ion-exchange resins. Most suspension polymers prepared as mol ding powders are poly(methyl methacrylate) copolymers containing up to 20% acrylate for reduced btittieness and improved processibiUty are also common. 

Copolymers Containing Carboxylic Groups. A newline of VP/acryhc acid copolymers in powdered form prepared by precipitation polymerization (147) from heptane have been introduced commercially (148). A wide variety of compositions and molecular weights are available, from... 

Polyethylene. Low pressure polymerization of ethylene produced in the Phillips process utilizes a catalyst comprised of 0.5—1.0 wt % chromium (VI) on siUca or siUca-alumina with pore diameter in the range 5—20 nanometers. In a typical catalyst preparation, the support in powder form is impregnated with an aqueous solution of a chromium salt and dried, after which it is heated at 500—600°C in fluid-bed-type operation driven with dry air. The activated catalyst is moisture sensitive and usually is stored under dry nitrogen (85). 

Sol-Gel Techniques. Sol-gel powders (2,13,15,17) are produced as a suspension or sol of coUoidal particles or polymer molecules mixed with a Hquid that polymerizes to form a gel (see Colloids SoL-GELtechnology). Typically, formation of a sol is foUowed by hydrolysis, polymerization, nucleation, and growth. Drying, low temperature calciaation, and light milling are subsequently required to produce a powder. Sol-gel synthesis yields fine, reactive, pseudo-crystalline powders that can be siatered at temperatures hundreds of degrees below conventionally prepared, crystalline powders. 

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