Polyacrylamide polyelectrolytes

Coagulation involves the addition of chemicals to alter the physical state of dissolved and suspended solids. This facilitates their removal by sedimentation and filtration. The most common primary coagulants are alum ferric sulfate and ferric chloride. Additional chemicals that may be added to enhance coagulation include activate silica, a complex silicate made from sodium silicate, and charged organic molecules called polyelectrolytes, which include large-molecular-weight polyacrylamides, dimethyl-diallylammonium chloride, polyamines, and starch. 

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]. 

Dry strength additives are usually water soluble, hydrophilic natural or synthetic polymers, the commercially most important of which are starch, natural vegetable gums and polyacrylamides. These polymers are often made in cationic form by the introduction of tertiary or quaternary amino groups into the polymer, and are therefore polyelectrolytes. They are thus also able to function to some extent as drainage and retention aids. 

The measurement of the surface tension of SDS solutions at constant polymer additions was performed to investigate any possible interactions between SDS and the polymers used in these experiments. The results, shown in Figure 2, indicate no interaction between SDS and either PAA or PAM. Interactions between similarly charged surfactant and polyelectrolyte are not common as electrical effects frequently dominate to prevent any hydro-phobic or hydrogen bonding interaction. The hydrophilic nature of the amide dipole of polyacrylamides has been suggested (11) as a possible factor in preventing interaction with sodium dodecylsulfate,... 

Further progress in the field of conformational phase transition in polymer gels, especially in polyelectrolyte gels, was achieved in the paper by Tanaka [4]. He investigated the swelling of polyacrylamide (PAA) networks, which were crosslinked by N,AT-methylenebisacrylamide (BAA), in the mixtures of water and acetone. When the quality of the solvent was made poorer (this happened when the concentration of acetone was increased or the temperature was lowered) shrinking of the samples was observed. Tanaka showed that at certain... 

Collagen, poly-L-lysine/serum proteins from cell culture medium Crosslinked polyacrylic acid/polyacrylamide multilayer films, PEG Coculture of rat adrenal medulla cells and mouse fibroblasts L929 Photopatteming of polyelectrolyte multilayer film 2009 [110]... 

A large number of macromolecules complementary to PMAA, namely polyvinylpyrrolidone, polyvinylpyridine, polyacrylamide, poly(vinyl alcohol), poly(ethylene oxide), oligoethylenimine, poly(sodium styrene sulfonate), polycations of the integral type ionen (2X) were used as P2 and P3. The pH of the media strongly influences the studied reactions of complex formation. For example, in PVPy + PVP + PMAA or OEI + PEO + PMAA systems in the add region, where weak polybases are completely protonized and PMAA does practically not dissodate, complexes with hydrogen bonds (PMAA-PVP or PMAA-PEO) are formed. In neutral medium weak polybases are partially ionizated and polyelectrolyte complexes (PMAA-PVPy, PMAA-OEI) are generated. In the alkaline medium formation of complexes has not been observed. 

Figure 5.39. Theoretical (a) and experimental (b) amount adsorbed as a function of the salt concentration for polyelectrolytes of varying charge density a, as Indicated. The theoretical figure was calculated for 0-6 and a surface charge density

Figure S.40. Charge due to adsorbed polyelectrolyte per unit of surface charge (Sa s) as a function of the total (added) amount of polyelectrolyte charge per unit surface charge (9 ). for cationic polyacrylamides of different molecular weights (expressed in K 3 kg/mole) (a) and of different polymer charge densities (b) adsorbed from salt-free solutions on anionic polyst3TFene latex. Redrawn from ref.

Waste water, containing a variety of colloids, is often treated by polymeric flocculants such as polyacrylamides to precipitate the colloidal material and make it better filterable. Quite often these flocculants are high-molecular-weight weakly charged polyelectrolytes. Bacterial suspensions resulting from biological waste water treatment must also be flocculated before they can be properly separated from the purified effluent by sedimentation or filtration. 

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