Poly particle size analysis

Vaisman et al. [103] formed a uniform, multi-walled nanotubes (MWNTs) distribution in water-soluble (poly(ethylene glycol)) and water-insoluble (polypropylene) polymers. In order to understand the surface-charge-related stability of the treated nanotubes solutions, zeta-potential measurements were applied. Quantification of the state of the M WNT dispersion was derived from particle-size analysis, while visual characterization was based on optical and electron microscopy. In order to estimate the nucleating ability of the surface-modified CNTs, the temperature of crystallization and the degree of crystallinity were calculated from differential scanning thermograms. 

Turbidity measurements are simple, fast and reproducible. Specific turbidity can successfully follow the particle size evolution during the course of emulsion polymerization and can be translated into weight average diameters. A combination of an on-line spectrophotometer with an on-line densitometer (to obtain concentration) would provide the potential to estimate Dw on-line, as well. An on-line determination of PSD s, for small particles however, would seem quite difficult due to the high correlation of their parameters. One should bear in mind that the above conclusions have been validated only for poly(vinyl acetate) latexes the analysis is currently being extened to other systems, such as polystyrene and poly(methyl-methacrylate). 

The analysis given above assumes a monodispersed colloid. Actual colloids are poly dispersed, that is, they contain a range of particle sizes (with corresponding effects on and t, see VIII). The particle size distribution is according to [81] accurately described by the T distribution... 

Iron nanoparticles prepared by pyrolysis of poly(ferrocenylsilanes) inside periodic mesoporous sihca displayed the absence of room-temperature hysteresis in the magnetization curves which shows their superparamagnetic behavior [55]. However, magnetic properties cannot always be easily interpreted. For example, for this material data analysis of magnetization curves resulted in the ambiguous conclusion that either particle size distribution is bimodal, or iron particles have an oxide layer which behaves as small superparamagnetic nanoparticles. So magnetic measurements should be combined with other techniques (probably, in this case, EXAFS may be useful) to allow more accurate evaluation of particle structure. 

Lee SC, Oh JT, Jang MH, Chung SI. Quantitative analysis of polyvinyl alcohol on the surface of poly(D, L-lactide-co-glycolide) microparticles prepared by solvent evaporation method Effect of particle size and PVA concentration. Journal of Controlled Release. May 20, 1999 59(2) 123-132. PubMed PMID 10332048. 

Other widely used ion-exclusion columns for the analysis of organic acids in combination with carbohydrates and alcohols are Aminex HPX-87 H (Bio-Rad, Hercules, CA, USA) and Rezex ROA (Phenomenex, Torrance, CA, USA), which are typically operated at elevated temperatures for optimal resolution. Both column substrates are totally sidfonated poly(styrene-co-divinyl-benzene)-based resins with a degree of cross-linking of 8% that slightly differ in particle size. Figure 5.7 illustrates the better resolution and peak shapes with less fronting effects for organic acid analysis on the Rezex ROA colunrn in comparison to the Aminex HPX-87H, while the overall analysis times are comparable. 

Other modifications to the reaction conditions of the Brust-Schiffrin method, such as a reduction temperature of — 78 °C and the use of a hyperexcess of hexanethiol, results in an Au38(thiolate)24, based on observations, LDI-TOF mass spectrometry, TGA analysis and elemental analysis [69]. The influence of preparation temperature on the size and monodispersity of dodecylthiol monolayer protected gold clusters has also been reported. Both and SAXS measurements show that higher temperatures increase polydispersity. This modification of poly-dispersity may be related to the existence of a dynamic exchange of thiols at the particle surface with thiols in the solvent [70]. 

Two reports have been published on the sonochemical preparation of nanosized ceria, Ce02 [133, 134]. Zhu and coworkers [133] synthesized nanocrystalline ceria (Ce02) particles via sonochemical and microwave assisted heating routes from aqueous solutions containing (NH4)2Ce(N03)6, hexamethylenetetramine and poly (ethylene glycol) (PEG Mw = 19,000). Analysis of the results showed that the products had a uniform shape, narrow size distribution, and displayed conspicuous quantum size effects. 

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