Dispersion, colloidal

In mass polymerization bulk monomer is converted to polymers. In solution polymerization the reaction is completed in the presence of a solvent. In suspension, dispersed mass, pearl or granular polymerization the monomer, containing dissolved initiator, is polymerized while dispersed in the form of fine droplets in a second non-reactive liquid (usually water). In emulsion polymerization an aqueous emulsion of the monomer in the presence of a water-soluble initiator Is converted to a polymer latex (colloidal dispersion of polymer in water). 

W. B. Russel, D. A. Saville, and W. R. Schowalter, Colloidal Dispersions, Cambridge University Press, Cambridge, UK, 1989. 

J. L. Moilliet, B. Collie, and W. Black, Surface Activity, E. F. N. Spon, London, 1961. D. H. Napper, Polymeric Stabilization of Colloidal Dispersions, Academic, New York,... 

Colloidal dispersions often display non-Newtonian behaviour, where the proportionality in equation (02.6.2) does not hold. This is particularly important for concentrated dispersions, which tend to be used in practice. Equation (02.6.2) can be used to define an apparent viscosity, happ, at a given shear rate. If q pp decreases witli increasing shear rate, tire dispersion is called shear tliinning (pseudoplastic) if it increases, tliis is known as shear tliickening (dilatant). The latter behaviour is typical of concentrated suspensions. If a finite shear stress has to be applied before tire suspension begins to flow, tliis is known as tire yield stress. The apparent viscosity may also change as a function of time, upon application of a fixed shear rate, related to tire fonnation or breakup of particle networks. Thixotropic dispersions show a decrease in q, pp with time, whereas an increase witli time is called rheopexy. 

Mapper D H 1983 Polymeric Stabilization of Colloidal Dispersions (London Academic)... 

Vrij A 1976 Polymers at interfaces and the interactions in colloidal dispersions Pure Appl. Chem. 48 471-83... 

Jenkins P and Snowden M 1996 Depletion flocculation in colloidal dispersions Adv. Colloid Interface Sc/. 68 57-96... 

Higashitani K and Matsuno Y 1979 Rapid Brownian coagulation of colloidal dispersions J. Chem. Eng. Japan 12 460-5... 

Rouw P W and de Kruif C G 1989 Adhesive hard-sphere colloidal dispersions fractal structures and fractal growth in silica dispersions Phys. Rev. A 39 5399-408... 

Russel W B, Seville D A and Schowalter W R 1989 Colloidal Dispersions (Cambridge Cambridge University Press) General textbook, emphasizing the physical equilibrium and non-equilibrium properties of colloids Shaw D J 1996 Introduction to Colloid and Surface Chemistry (Oxford Butterworth-Heinemann)... 

Globular protein (Section 27 20) An approximately spheri cally shaped protein that forms a colloidal dispersion in water Most enzymes are globular proteins Glycogen (Section 25 15) A polysaccharide present in animals that IS denved from glucose Similar in structure to amy lopectin... 

D. H. Napper, Polymeric Stabilisation of Colloidal Dispersions, Academic Press, London, 1983. 

K. L. Mittal, ed.. Colloidal Dispersions and Micellar Behavior, ACS Symposium Series 9, American Chemical Society, Washington, D.C., 1975. 

D. E. Napper, Polymeric Stabili tion of Colloidal Dispersion, Academic Press, Inc., New York, 1983. 

X being the average displacement of the particles in the time t. The obvious difference between these colloidal dispersions aird the catalyst particles on the surface of a support, is that the above model would require that the particles... 

Poly(vinyl chloride) is commercially available in the form of aqueous colloidal dispersions (latices). They are the uncoagulated products of emulsion polymerisation process and are used to coat or impregnate textiles and paper. The individual particles are somewhat less than 1 p,m in diameter. The latex may be coagulated by concentrated acids, polyvalent cations and by dehydration with water-miscible liquids. 

The butter fat is a coarse dispersion readily removable on standing or by a centrifuging operation. The casein will be present in the skimmed milk as colloidally dispersed micelles of diameter of the order of 10 cm, and is associated with calcium and phosphate ions. 

Eq. (101) is the multidensity Ornstein-Zernike equation for the bulk, one-component dimerizing fluid. Eqs. (102) and (103) are the associative analog of the singlet equation (31). The last equation of the set, Eq. (104), describes the correlations between two giant particles and may be important for theories of colloid dispersions. The partial correlation functions yield three... 

In Sec. 3 our presentation is focused on the most important results obtained by different authors in the framework of the rephca Ornstein-Zernike (ROZ) integral equations and by simulations of simple fluids in microporous matrices. For illustrative purposes, we discuss some original results obtained recently in our laboratory. Those allow us to show the application of the ROZ equations to the structure and thermodynamics of fluids adsorbed in disordered porous media. In particular, we present a solution of the ROZ equations for a hard sphere mixture that is highly asymmetric by size, adsorbed in a matrix of hard spheres. This example is relevant in describing the structure of colloidal dispersions in a disordered microporous medium. On the other hand, we present some of the results for the adsorption of a hard sphere fluid in a disordered medium of spherical permeable membranes. The theory developed for the description of this model agrees well with computer simulation data. Finally, in this section we demonstrate the applications of the ROZ theory and present simulation data for adsorption of a hard sphere fluid in a matrix of short chain molecules. This example serves to show the relevance of the theory of Wertheim to chemical association for a set of problems focused on adsorption of fluids and mixtures in disordered microporous matrices prepared by polymerization of species. 

We introduce, for the sake of convenience, species indices 5 and c for the components of the fluid mixture mimicking solvent species and colloids, and species index m for the matrix component. The matrix and both fluid species are at densities p cr, Pccl, and p cr, respectively. The diameter of matrix and fluid species is denoted by cr, cr, and cr, respectively. We choose the diameter of solvent particles as a length unit, = 1. The diameter of matrix species is chosen similar to a simplified model of silica xerogel [39], cr = 7.055. On the other hand, as in previous theoretical works on bulk colloidal dispersions, see e.g.. Ref. 48 and references therein, we choose the diameter of large fluid particles mimicking colloids, cr = 5. As usual for these dispersions, the concentration of large particles, c, must be taken much smaller than that of the solvent. For all the cases in question we assume = 1.25 x 10 . The model for interparticle interactions is... 

FIG. 1 The mean force potential acting between colloidal species, /3fV (r), in adsorbed colloidal dispersion. In parts (a) and (b) the matrix density is taken as negligibly small, = 10 and = 0.193, respectively. In both parts, the evolution of the mean force potential with solvent density is shown p = 0.2, 0.3 and 0.4 (solid, dashed, and dotted lines, respectively). In part (c) the evolution of the PMF on matrix density is presented. The solvent density is held constant, p =0.3 the matrix density is Pmcr = 0.193, 0.386, and 0.772 (dotted, dashed, and solid lines, respectively). The diameter of the matrix species is = 7.055. The density of colloids is Pcg] = 10 , with Uc = 5, in all the cases in question. 

Stabilization of Colloidal Dispersions by Polymer Adsorption, Tatsuo Sato and Richard Ruch... 

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