High colloidal stability

Novel thermally responsive polymeric nanoparticles that show high colloidal stability were prepared by Laukkanen et al. via emulsion polymerisation of VCL in the presence of the amphiphilic macromonomer cw-methoxy polyethylene oxide undecyl a-methacrylate (MAC11EO42) (Fig. 15) [177,178,182]. The macromonomer itself proved to be highly sur-... 

Citrate-capped Au NPs have been coated with a layer composed of the double hydrophilic block copolymer polyethylene oxide)-block-poly(2-(dimethylamino)eth-yl methacrylate)-SH (PEO-b-PDMA-SH) leading to core-shell, almost spherical, Au NPs of about 18 nm. The shell cross-linking of these hybrid Au NPs gives rise to high colloidal stability [122]. 

A series of amphiphilic diblock macromonomers were successfully used as steric stabilizers in the emulsion polymerization styrene [98]. Copolymerization led to the formation of polymer latexes of high colloidal stability. These... 

The molecules of both HSl and HS2 have a high colloid stability due to their very low collision efficiency and small size which prevent them from settling under normal gravitational acceleration. Their separation in a centrifuge with a g value of some thousands is still practically inefficient. This fact is used for sedimentation analysis to investigate the destabilization and aggregation rate of the coagulation process of humic substances. 

Fundamental concepts of starch chemistry provide an interpretation of its function and behavior in various food uses. The characteristics of modified starches depend on granule structure and on specific size and shape of the component molecules. Most native starches contain both linear and branched polysaccharides. The linear fraction is responsible for gel formation and for various retrogradation effects, the branched fraction for high colloidal stability and good suspending qualities. Starches are employed in the food industry as gel formers, thickening agents, and colloidal emulsifiers. Desired characteristics can frequently be enhanced by choice of an appropriate modified starch. The various food uses are individually discussed from the standpoint of molecular behavior and optimal types of modification. 

Elaissari and coworkers recently reported the synthesis of hydrophilic aminodex-tran containing magnetic latex using the combination of seeded and miniemulsionlike polymerization processes. The characterization of the latex demonstrated that the particles were cationically charged, hydrophilic, and have a high colloidal stability irrespective of the aminodextran immobilization process [149]. 

Mori and Kawaguchi reported the preparation of magnetic polystyrene particles containing 30 wt% of magnetite. Magnetic polystyrene particles of 300 nm were produced and easily separated when persulphate, KPS or APS initiator was used. Conversely, due to high colloidal stability, the latex prepared by oil-soluble initiator (for instance AIBN) was not easy to separate, and the magnetite nanoparticles were located on the surface of the polystyrene latex. A mixture of initiators resulted in intermediate properties compared to individual systems [170]. 

The catalytic reduction of 4-nitrophenol to 4-aminophenol has been used for the analysis of the catalytic activity of the Pt NPs. The Pt NCs exhibit a high catalytic activity and turnover numbers as high as 1580 50, which is among the highest turnover numbers measured for this reaction. Hence, the composite particles consisting of the SPBs and the Pt NCs present a system with high colloidal stability that may be used for catalysis in an aqueous environment. 

The length for fiber settling was short for the above sample and was probably at several micrometers. This length depends on many factors. Fibers with a long soluble corona block and a short insoluble core block(s) should have high colloidal stability. Decreasing the core diameter should increase fiber colloidal stability as well. 

Block copolymers composed of a cationic segment and a hydrophilic segment spontaneously associate with polyanionic DNA to form block copolymer micelles. The distinct feature of the structure is that the core of the polyion complex between DNA and the polycation is coated by a layer of the hydrophilic polymer. The characteristic core-shell structure endows the complex a high colloidal stability and reduced interaction with blood components [12]. 

The typical nucleation mechanism coupled with high colloidal stability is achieved by the use of the stabilizing substances. The result is polymer particles with size comparable to nanoreactor precursors of the polymerization process, as shown in Fig. 8.4. Bearing this characteristic in mind, there is a need for optimal conditions of operation, mechanisms, and dispersion stability. These characteristics play a vital role on the particle morphology of the polymers obtained at the end of the process [26,34]. 

Dragan ES, Mihai M, Schwarz S (2006) Polyelectrolyte complex dispersions with a high colloidal stability controlled by the polyion structure and titrant addition rate. Colloid Surf A... 

A thorough analysis [16, 17, 18, 25] of the hydrodynamic volumic fraction ( h) dependence of the viscosity ri) of mono-layer and double-layer sterically stabilized magnetic fluids of high colloidal stability evidenced that this is best described by the theoretical formula obtained by Chow [27] ... 

A. Pourjavadi, S.H. Hosseini, M. Alizadeh, and C. Bennett, Magnetic pH-responsive nanocarrier with long spacer length and high colloidal stability for controlled delivery of doxorubicin, Colloids SurfB Biointerfaces, 116C, 49-54,2013. 

The inherently high colloid stability of nano-emulsions can be well understood from a consideration of their steric stabilisation (when using nonionic surfactants and/or polymers) and how this is affected by the ratio of the adsorbed layer thickness to droplet radius, as will be discussed below. 

Nanoemulsions are only kinetically stable. They have to be distinguished from microemulsions (that cover the size range 5-50 nm) which are mostly transparent and thermodynamically stable. The long-term physical stability of nanoemulsions (with no apparent flocculation or coalescence) makes them unique and they are sometimes referred to as approaching thermodynamic stability . The inherently high colloid stability of nanoemulsions can be well understood from a consideration of their steric stabilization (when using nonionic surfactants and/or polymers) and how this is affected by the ratio of the adsorbed layer thickness to droplet radius as will be discussed below. 

The inherently high colloid stability of nanoemulsions when using polymeric surfactants is due to their steric stabilization. The mechanism of steric stabilization was discussed above. As shown in Fig. 1.3 (a), the energy-distance curve shows a shallow attractive minimum at separation distance comparable to twice the adsorbed layer thickness 28. This minimum decreases in magnitude as the ratio between adsorbed layer thickness to droplet size increases. With nanoemulsions the ratio of adsorbed layer thickness to droplet radius (8/R) is relatively large (0.1 0.2) when compared with macroemulsions. This is schematically illustrated in Fig. 1.28 which shows the reduction in with increasing 8/R. 

If the nanometer particles consist of ferri or ferromagnetic nm-particles such as magnetite or iron, the prepared magnetic sols show — besides the high colloidal stability — a superparamagnetic behavior no hysteresis in the magnetization curve. 

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