Polyelectrolytes anionicity

This exclusion is based on size of the ion and leads to the formation of the Don-nan potential, first mentioned in Chapter 2. Its origin can be explained using the simplest case, involving a uni-univalent electrolyte (NaCl) and a large polyelectrolyte anion V, which is present only in the left compartment (marked with a in Fig. 6.4) and carries z negative charges. We again recall two conditions that must be satisfied at this membrane equilibrium ... 

Cationic polyelectrolyte Anionic polyelectrolyte Amount of matrix weight 0 Adsorption half-time, minutes... 

Influent concentrations and residual concentrations of cationic surfactants, anionic surfactants, cationic polyelectrolyte, anionic polyelectrolyte, proteins, colloids, oxygen, ozone, detergents, suspended sohds, and so on, in the adsorptive bubble separation systems can be determined by the analytical methods reported in the literature (82,127-149). 

Most of the results reported herein on the sorption of polycations by natural keratins have been obtained on simplified model systems. The rationale behind such an approach was to seek to determine the fate of sorbing polymer under well-defined conditions and so to obtain mechanistic insight. The results have clearly indicated that both adsorption and absorption processes can occur. They have also shown that the nature, extent, and consequences of polycation sorption can all be influenced by the presence of surfactant. In general, nonionic surfactants have a small effect on sorption, because of low interaction while cationic surfactants can have a very large effect because of competition for the sorption sites. Because of interaction and complex formation with cationic polyelectrolytes anionic surfactants can exercise an intermediate, but potentially very important, influence. 

Polyelectrolytes, Anionic, Blend (3> 12S F. . Polyester While Enamel, Water Redudbla... 

This picture is undoubtedly oversimplified. Different sites are switched at different potentials, and when A is A relatively immobile (e.g., a polyelectrolyte anion)cation movement accommodates the oxidation/reduction process. 

Polyelectrolyte complex membranes are phase-inversion membranes where polymeric anions and cations react during the gelation. The reaction is suppressed before gelation by incorporating low molecular weight electrolytes or counterions in the solvent system. Both neutral and charged membranes are formed in this manner (14,15). These membranes have not been exploited commercially because of then lack of resistance to chemicals. 

Approximately a minimum of 1 to 5,000 is required before complexation is no longer dependent on molecular weight for small anions such as KI and l-ariiLinonaphthaLine-8-sulfonate (ANS) (86,87). The latter anion is a fluorescent probe that, when bound in hydrophobic environments, will display increased fluorescence and, as expected, shows this effect in the presence of aqueous PVP. PVP, when complexed with Hl, shrinks in si2e as it loses hydrodynamic volume, possibly because of interchain complexation. ANS, on the other hand, causes the polymer to swell by charge repulsion because it behaves like a typical polyelectrolyte (88). 

Polyelectrolytes are classified into three main groups nonionic, anionic, and cationic depending upon the nature of the residual charge on the polymer in aqueous solution as shown in Table 1. 

Morishima et al. [75, 76] have shown a remarkable effect of the polyelectrolyte surface potential on photoinduced ET in the laser photolysis of APh-x (8) and QPh-x (12) with viologens as electron acceptors. Decay profiles for the SPV (14) radical anion (SPV- ) generated by the photoinduced ET following a 347.1-nm laser excitation were monitored at 602 nm (Fig. 13) [75], For APh-9, the SPV- transient absorption persisted for several hundred microseconds after the laser pulse. The second-order rate constant (kb) for the back ET from SPV- to the oxidized Phen residue (Phen+) was estimated to be 8.7 x 107 M 1 s-1 for the APh-9-SPV system. For the monomer model system (AM(15)-SPV), on the other hand, kb was 2.8 x 109 M-1 s-1. This marked retardation of the back ET in the APh-9-SPV system is attributed to the electrostatic repulsion of SPV- by the electric field on the molecular surface of APh-9. The addition of NaCl decreases the electrostatic interaction. In fact, it increased the back ET rate. For example, at NaCl concentrations of 0.025 and 0.2 M, the value of kb increased to 2.5 x 108 and... 

Anionic Polyelectrolytes Containing Nucleic Acid Bases.136... 

Cordes et al995 carried out alkaline hydrolyses of p-nitrophenylhexanoate 55 (PNPH) in the presence of poly-4-vinylpyridine partially quaternized with dodecyl-bromide and ethylbromide (QPVP). They also found that the polyelectrolytes are increasingly effective as catalysts with an increasing ratio of dodecyl to ethyl groups, and the hydrophobic interactions are important in determining the catalytic efficiency. They observed the inhibitory effects of several gegen-anions fluoride ions are the weakest inhibitor, and nitrate is the strongest (F- < Cl < S04 [Pg.159]

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. 

As a polycation, chitosan spontaneously forms macromolecular complexes upon reaction with anionic polyelectrolytes. These complexes are generally water-insoluble and form hydrogels [90,91]. A variety of polyelectrolytes can be obtained by changing the chemical structure of component polymers, such as molecular weight, flexibility, fimctional group structure, charge density, hydrophilicity and hydrophobicity, stereoregularity, and compatibility, as... 

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... 

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