Polyelectrolytes solubility

Substituted PPVs have been prepared using similar techniques. The earliest reports described methyl substituents (104,105), and more recentiy alkoxy substituents on the aromatic ring have been incorporated into the polymer stmctures (107—109). The advantage of long-chain alkoxy (butoxy or hexyloxy) substituents is that not only is the precursor polyelectrolyte soluble, but after conversion the substituted PPV is also soluble (110—112). 

Rheological Nature Gum Arabica is a polyelectrolyte soluble in water over a wide range of concentration below 40% concentration pseudo-plastic characteristics are observed, denoted by a decrease in viscosity. VN th increasing temperature the relative viscosity and density of gum Arabica solution decreases. 

CMC is an anionic linear polyelectrolyte, soluble in both cold and hot water, and the molecular conformation in aqueous solution strongly depends on the concentration, ionic strength, and pH. The solution viscosity decreases during heating. Nevertheless, the solution behavior strongly depends on the molar mass and the DS. 

The commercial product has a D.S. of 0.3 to 0.7. It is purified by extraction with alcohol-water mixtures to remove salt and sodium glycolate. The product is a polyelectrolyte soluble in polar solvents. 

For PAA and PVS, the principle factor influencing adsorption under these conditions is the degree of ionization of the polymers. Figure 2 shows the percent ionization of PAA (pKa = 4.5) and PVS (pKa <2) across a wide range of pH. As shown in the figure, PAA is only 24% ionized at pH = 4, while PVS is essentially 1(X)% ionized. Therefore, the charge density on PVS is much greater than that on PAA at pH = 4. This difference has several ramifications in terms of electrostatic interactions and polyelectrolyte solubility. 

The adsorption of DNA films assembled from oligonucleotides composed of two homopolymeric diblocks (polyA G and polyTnCn) were studied in the presence of salt. The growth of fihn increased with salt concentration [22]. The studies on polyelectrolyte complexation have offered wide applications such as water treatment, surface modification, dmg delivery system, tissue engineering. To understand the formation of protein-polyelectrolyte complex is important due to the interaction between polyanions or polycations with protein macromolecules or polyelectrolytes. Soluble complexes can be formed and amphorous can be precipitated with the interaction of molecules. Complex formation is generally performed in the bulk solutions. Potentiometry, conductometry, viscosimetry, turbidimetry, or electrophoretic and quasi-elastic light scattering are used to follow... 

Two inorganic water-soluble polymers, both polyelectrolytes in their sodium salt forms, have been known for some time poly(phosphoric acid) (12) and poly(siHcic acid) (13). A more exciting inorganic water-soluble polymer with nonionic... 

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). 

Polyelectrolytes refers to all water-soluble organic polymers used for clarification, whether they function as coagulants or flocculants. Water-soluble polymers may be classified as follows ... 

Some commercial durable antistatic finishes have been Hsted in Table 3 (98). Early patents suggest that amino resins (qv) can impart both antisHp and antistatic properties to nylon, acryUc, and polyester fabrics. CycHc polyurethanes, water-soluble amine salts cross-linked with styrene, and water-soluble amine salts of sulfonated polystyrene have been claimed to confer durable antistatic protection. Later patents included dibydroxyethyl sulfone [2580-77-0] hydroxyalkylated cellulose or starch, poly(vinyl alcohol) [9002-86-2] cross-linked with dimethylolethylene urea, chlorotria2ine derivatives, and epoxy-based products. Other patents claim the use of various acryUc polymers and copolymers. Essentially, durable antistats are polyelectrolytes, and the majority of usehil products involve variations of cross-linked polyamines containing polyethoxy segments (92,99—101). 

Poly(arylene vinylenes). The use of the soluble precursor route has been successful in the case of poly(arylene vinylenes), both those containing ben2enoid and heteroaromatic species as the aryl groups. The simplest member of this family is poly(p-phenylene vinylene) [26009-24-5] (PPV). High molecular weight PPV is prepared via a soluble precursor route (99—105). The method involves the synthesis of the bis-sulfonium salt from /)-dichloromethylbenzene, followed by a sodium hydroxide elimination polymerization reaction at 0°C to produce an aqueous solution of a polyelectrolyte precursor polymer (11). This polyelectrolyte is then processed into films, foams, and fibers, and converted to PPV thermally (eq. 8). 

Because of the aqueous solubiUty of polyelectrolyte precursor polymers, another method of polymer blend formation is possible. The precursor polymer is co-dissolved with a water-soluble matrix polymer, and films of the blend are cast. With heating, the fully conjugated conducting polymer is generated to form the composite film. This technique has been used for poly(arylene vinylenes) with a variety of water-soluble matrix polymers, including polyacrjiamide, poly(ethylene oxide), polyvinylpyrroHdinone, methylceUulose, and hydroxypropylceUulose (139—141). These blends generally exhibit phase-separated morphologies. 

Water-soluble polymers and polyelectrolytes (e.g., polyethylene glycol, polyethylene imine polyacrylic acid) have been used success-hilly in protein precipitations, and there has been some success in affinity precipitations wherein appropriate ligands attached to polymers can couple with the target proteins to enhance their aggregation. Protein precipitation can also be achieved using pH adjustment, since proteins generally exhibit their lowest solubility at their isoelectric point. Temperature variations at constant salt concentration allow for frac tional precipitation of proteins. 

Interest in the chemistry of water-soluble polymers (polyelectrolytes) has been continually increasing during the past 45 years. The tremendous scope of utility for water-soluble polymers has led to a vigorous search for new materials and the rapid development of polyelectrolytes into a dynamic field of industrial research. Growth in this field has been especially rapid since 1960 and today, many companies are engaged in synthesis and applications research on polyelectrolytes that are primarily used in four main marketing areas water treatment, paper, textiles, and oil recovery [1]. Polyacrylamide gel was also used as soil conditioner [2-4]. 

The extensive industrial and commercial utilization of water-soluble polymers (polyelectrolytes) in water treatment has been developed based on the charge along the polymer chains and the resultant water solubility. The use of water-soluble polymers in water treatment has been investigated by several authors [5-26] in the recovery of metals radioactive isotopes, heavy metals, and harmful inorganic residues. This allows recycling water in the industrial processes and so greatly saves... 

Soluble PPPs 6 are known today that contain, not only alkyl substituents, but also alkoxy groups, as well as ionic side groups (carboxy and sulfonic acid functions) [21], which are able to form PPP polyelectrolytes. 

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],... 

The precipitation of polyelectrolytes by the addition of multivalent counterions may be explained in these terms. When there are no multivalent ions in solution there is a strong repulsive force between polyions and the osmotic pressure is large. The solubility of polyions is a result of these repulsive forces. 

Michaeli (1960) opposed these views. He concluded that whatever the exact mechanism was, the binding of divalent cations caused contraction and coiling of the polyelectrolyte as was the case with adds. He disagreed with the concept of ionic crosslinking. The phenomenon of precipitation could be explained simply in terms of reduced solubility. From this he concluded that precipitation took place in an already coiled molecule and the matrix consisted of spherical macromolecules containing embedded cations. 

Although this account of gelation is made with reference to organic polyelectrolytes, it is of wider application and may be applied to phosphoric acid cements. Orthophosphoric acid solutions used in these cements contain aluminium, and soluble aluminophosphate complexes are formed. Some appear to be multinuclear and there is evidence for polymers based on the bridging Al-O-P unit. These could be termed polyelectrolytes (Akitt, Greenwood Lester, 1971 Wilson et al., 1972 O Neill et al., 1982). 

Solutions of polyelectrolytes contain polyions and the free (individual) counterions. The dissociation of a polyacid or its salt yields polyanions, and that of a polybase or its salt yields polycations, in addition to the simple counterions. The polyampholytes are amphoteric their dissociation yields polyions that have anionic and cationic functions in the same ion and often are called zwitterions (as in the case of amino acids having HjN and COO groups in the same molecule). Such an amphoter will behave as a base toward a stronger acid and as an acid toward a stronger base its solution properties (particularly its effective charge) will be pH dependent, and an isoelectric point (pH value) exists where anionic and cationic dissociation is balanced so that the polyion s charges add up to zero net charge (and solubility is minimal). 

Inorganic polyelectrolytes exist, too polyphosphates, -0-P(=0)(-0H)-, are the most common (soluble) ones. 

In solutions, the counterions of poly electrolytes are HjO (for the polyacids) and OH (for the polybases), cations such as K+ and Na, or anions such as Cl (for the polysalts). The addition of polyvalent counterions (such as Ca, Mg, Cu, AT ) produces ionic cross-linking interfering with solubility The polyelectrolyte precipitates and may be redissolved upon addition of a strong acid (such as HCl). This can be regarded as a special case of ion exchange. 

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