Colloidal stable

E.I. Du Pont de Nemours, Colloidal stable solvent cement compositions comprising chloro-prene polymers, phenolic resins and polyisocyanate, U.S. Patent 3,318,834, 9 May, 1967. 

A number of diblock copolymers of NIPAM and hydrophobic comonomers have been prepared by various groups and assessed in terms of micellar structure, thermosensitivity, and applications. For example, PS-fo-PNIPAM was shown to form either micelles consisting of a PS core and a PNIPAM corona, or vesicles. The assemblies were colloidally stable at elevated temperature [262-266]. 

Taken together, the experimental observations reported in the previous sections suggest that the formation of colloidally stable particles heated above their phase-transition temperature may be a universal phenomenon, taking place not only in aqueous polymer solutions, but also in solutions of polymers that can undergo a coil-globule transition in organic solvents. 

Reversal of coagulation or flocculation, i.e., colloidally stable suspension or emulsion. [2]... 

Under what conditions are colloids stable Explain qualitatively (with schematic diagrams) the forces between colloidal particles. How does the force of repulsion between them vary with concentration As the concentration of the colloid increases, there is the tendency to coagulate and in fact the critical concentration for coagulation gets less as the valence of the ions present increases (Schulze-Hardy rule). Give a detailed, although qualitative, rationalization of this law. (Bockris)... 

The colloidal stable polymer dispersions, the monodisperse polymer particles, and high conversions (85-100%) can be obtained with most of the other macromonomers (MAL,VB, and MA) of PEO (MW>PEO=2000)) [76]. Also, when macromonomers are used (3.1 wt% based on styrene), there is practically no coagulum produced. This is not the case in the presence of polymerizable PEO surfactants (surfmer I R1=CH3(CH2)11-, R2=H, n=34 and surfmer II R =CH3 (CH2)n-, R2=H, n=42) despite the higher amounts of stabilizer used (up to 60 wt% of coagulum). Furthermore, the particles are more monodisperse with PEO macromonomer (Dw/Dn=1.025 for PEO-MA and 1.13 for PVPo) compared to those with surfmer. Comparatively poorer results were obtained with conventional surfactants such as ethoxylated nonylphenol, even when used in large amounts. 

In later stages of the polymerization it is possible to have a situation in which the larger particles bear enough charges to be colloidally stable, but where N r is not large enough to prevent nucleation. A steady state may soon be reached in which dN/dt = 0. Then, according to Equation 3,... 

The process in which small amounts of added hydrophilic colloidal material make a hydrophobic colloid more sensitive to coagulation by electrolyte. Example the addition of polyelectrolyte to an oil-in-water emulsion to promote demulsification by salting out. Higher additions of the same material usually make the emulsion less sensitive to coagulation, and this is termed protective action or protection . The protected, colloidally stable dispersions that result in the latter case are termed protected lyophobic colloids . 

The chemistry and physics of such particles represent a separate, rapidly developing field. The consideration of this field (even if brief) is beyond the scope of this review. From the standpoint of this review, of most interest is the fact that melting of similar films often produces stable colloid solutions of metals in non-aqueous media. Early works in this field were summarized in review [19]. Among later results, noteworthy is the stabilization of metal nanoparticles in tertiary amines, which appear to be a unique medium for formation of stable colloid solutions of a wide variety of metals [20, 21]. Metal colloids stable for, at least, several years were obtained through the intermediate formation of thin films of co-condensates of metals with amines. 

Colloids Stable mixtures in which particles of rather large sizes (ranging from 1 nm to 1 tm) are dispersed throughout another substance. 

The W values [65] for a dispersion of AI2O3 as a function of pH and KNO3 salt concentration are shown in Figure 10.27. The AI2O3 particles are colloidally stable far away from their isoelectric point (i.e., pH 8.9). As the salt concentration is increased the zeta potential decreases and the colloid stability ratio, W, decreases. Near the isoelectric point there is no electrostatic repulsion, giving a rapid coagulation. 

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