Particle polyelectrolytes

Returning again to ionizing media, a combination of these two effects can be employed by grafting to a polymer cfffe particle polyelectrolyte chains. This is illustrated schematically in Fig. 3. It provides a combinatorial effect of electrostatic and steric interactions. These will have different interactive ranges as illustrated in Fig. 3 by the dotted line for the electrostatic range and the dashed line for steric effects. 

Various combinations of synthetic polyelectrolytes are applied to the formation of polyelectrolyte shells onto colloid particles. Polyelectrolytes are divided into weak and strong ones. The examples of the first ones are sodium poly(styrene sulfonate) (PSS) and polyaniline propanesulfonic acid. Polyacrilic acid is an example of weak polyelectrolyte. Both examples are polyanions. Polyamines with various number of assistants at the atom of nitrogen are basically used as polycation components, for example poly(allylamine hydrochloride), polyethylenimin, etc. 

Chemicals can be added to the water in clarifiers, which are tanks that contain mixers that cause sufficient turbulence to create contact between the chemical and the solids. Coagulation/flocculation chemicals can also be added in flotation units to aid in attaching gas bubbles to the solid particles. Polyelectrolytes added to the feed stream to filtration units have proven effective at increasing filtration efficiency. 

The natural process of bringing particles and polyelectrolytes together by Brownian motion, ie, perikinetic flocculation, often is assisted by orthokinetic flocculation which increases particle coUisions through the motion of the fluid and velocity gradients in the flow. This is the idea behind the use of in-line mixers or paddle-type flocculators in front of some separation equipment like gravity clarifiers. The rate of flocculation in clarifiers is also increased by recycling the floes to increase the rate of particle—particle coUisions through the increase in soUds concentration. 

The kinetics of vinyl acetate emulsion polymeriza tion in the presence of alkyl phenyl ethoxylate surfactants of various chain lengths indicate that part of the emulsion polymerization occurs in the aqueous phase and part in the particles (115). A study of the emulsion polymerization of vinyl acetate in the presence of sodium lauryl sulfate reveals that a water-soluble poly(vinyl acetate)—sodium dodecyl sulfate polyelectrolyte complex forms, and that latex stabihty, polymer hydrolysis, and molecular weight are controlled by this phenomenon (116). 

Polymer A chemical formed by the union of many monomers (a molecule of low molecular weight). Polymers are used with other chemical coagulants to aid in binding small suspended particles to form larger chemical floes for easier removal from water. All polyelectrolytes are polymers, but not all polymers are polyelectrolytes. 

In addition it should be added that microdisperse forms of CP can precipitate proteins from solutions. Figs. 21-23 show that CP microdispersions with particle size of 1-2 pm precipitate serum albumin from solutions [81] in complete agreement with general flocculation laws for polyelectrolytes. The figs, show an extreme... 

The interpretation of the relationships obtained here is based on the same principles of polyfunctional interaction between CP and organic ions which are considered in sections 3.1-3.3. The dispersion of CP grains to a certain size (1-10 pm) yields particles retaining the ability of polyfunctional interaction with organic ions. Simultaneously with increasing dispersion, the mobility of elements of the crosslinked structure also increases, which favors additional interaction. Further dispersion of CP (d 0.1 pm) gives so weak networks that the spatial effect of polyfunctional interaction with organic ions drastically decreases similar to linear polyelectrolytes [64]. 

These condensed tannins and their derivatives, all of high molecular weight, function as anionic polyelectrolyte sludge conditioners, tending to sequester hardness salts and hinder their precipitation as crystalline scales. In addition, when precipitation does occur, the condensed tannins coagulate the particles, resulting in a mobile sludge that can be easily blown down. 

The potential between the Helmholtz double layer of a charged particle. Important for assessing the suitability of polyelectrolyte chemicals because it can be easily measured, unlike some other electrokinetic forces. 

The process of adsorption of polyelectrolytes on solid surfaces has been intensively studied because of its importance in technology, including steric stabilization of colloid particles [3,4]. This process has attracted increasing attention because of the recently developed, sophisticated use of polyelectrolyte adsorption alternate layer-by-layer adsorption [7] and stabilization of surfactant monolayers at the air-water interface [26], Surface forces measurement has been performed to study the adsorption process of a negatively charged polymer, poly(styrene sulfonate) (PSS), on a cationic monolayer of fluorocarbon ammonium amphiphilic 1 (Fig. 7) [27],... 

The penetration of ions from the subphase into the shell of spread particles is a general phenomenon and can be used to modify and functionalize the particle surface. For example, metal ions, such as Ba and Fe, or cationic polyelectrolytes, such as the polycation of polyallylamine, can be adsorbed at anionic particles, while anionic water-soluble dyes, such as phthalocyanine tetrasulfonic acid and 1.4-diketo-3.6-diphenylpyrrolo[3.4-c]pyrrole-4, 4 -disulfonic acid (DPPS) [157], can be adsorbed at cationic particles. However, since only a monolayer of the dye is adsorbed, a deep coloration of the particles is not obtained unless a dye with very high absorption coefficient is used [156],... 

Serizawa and Akashi [95] analyzed the monolayer adsorption of polystyrene latex particles with cationic polyvinylamine grafted on their surface, while Serizawa et al. [96,97] used commercial anionic latex particles. Both types of particles were adsorbed on polyelectrolyte-coated substrates previously prepared by alternating adsorption of cationic and anionic polyelectrolytes such as polyallylamine hydrochloride (PAH) and polystyrene sulfonate sodium salt (PSS) according to the method described by Decher [164]. Using... 

Nonhomogenous distribution of charge inside fully condensed DNA/polycation particles has been discussed earlier, in Section lll.F.l. Since it takes only 0.9 equivalents of positive charges to condense DNA in aqueous environment, there should be an excess of positive charge on the surface of completely condensed DNA/polycation particles. This fact opens the opportunity to form multilayered structures based on alternations of polyelectrolytes of opposite charge. Details of this approach of DNA/polyion self-assembly are discussed in Section III.F.9. 

Electrophoresis measurements provide a qualitative indication of the assembly of polymer multilayers on colloids [49,50], The -potential as a function of polyelectrolyte layer number for negatively charged polystyrene (PS) particles coated with poly(diallyldimethylam-monium chloride) (PDADMAC) and poly(styrenesulfonate) (PSS) are displayed in Figure... 

FIG. 5 SEM micrographs of (a) uncoated PS latices and (b) polyelectrolyte-modified PS latices coated with S1O2/PDADMAC. An increase in snrface ronghness and diameter can be clearly seen for the particles coated with Si02/PDADM AC (compare b with a). (From Ref. 58.)... 

FIG. 7 Confocal laser scanning microscopy image of a fonr-layer polyelectrolyte/CdTe(S) nanocrystal shell assembled on 1.5-p,m-diameter ME particles. The polyelectrolyte film consists of two bUayers of PAH and PSS. (From Ref. 76.)... 

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