Anionic polyelectrolytes, characteristics

Pradip, Premachandran, R.S., and Malghan, S.G., Electrokinetic behaviour and dispersion characteristics of ceramic powders with cationic and anionic polyelectrolytes, Bull. Mater. Sci, 17, 911, 1994. 

A flocculation process. This serves to harvest the bacterial cells, i.e. remove cells from the growth medium, and ultimately to form the support matrix. This stage in the process is achieved by the sequential addition of cationic and anionic polyelectrolytes. The two polyelectrolytes used are capable of forming a polysalt complex and it is believed that this complex structure, in which the bacterial cells are embedded, gives rise to the product s robust physical characteristics whilst allowing the desired enzyme performance. 

The intrinsic viscosity (rj) is a characteristic value of a single macromolecule in a given solvent and it is a measure of the hydrodynamic volume occupied by the polymer itself. It depends primarily on the molar mass (Mw), chain rigidity, and solvent quality. For anionic polyelectrolytes the presence of macroions and counterions in aqueous media causes coil expansion by intrachain electrostatic repulsion and extra dissipation of energy, thus explaining why the intrinsic viscosity of a polyelectrolyte can be higher than that of a neutral rodlike macromolecule of equal size. Thus, (rj) usually increases with an increase in the charge density of the macroion. 

Premachandran RS, Malghan SG. Dispersion characteristics of ceramic powders in the application of cationic and anionic polyelectrolytes. Powder Technol 1994 79 53-60. 

In a related application, polyelectrolyte microgels based on crosslinked cationic poly(allyl amine) and anionic polyfmethacrylic acid-co-epoxypropyl methacrylate) were studied by potentiometry, conductometry and turbidimetry [349]. In their neutralized (salt) form, the microgels fully complexed with linear polyelectrolytes (poly(acrylic acid), poly(acrylic acid-co-acrylamide), and polystyrene sulfonate)) as if the gels were themselves linear. However, if an acid/base reaction occurs between the linear polymers and the gels, it appears that only the surfaces of the gels form complexes. Previous work has addressed the fundamental characteristics of these complexes [350, 351] and has shown preferential complexation of cationic polyelectrolytes with crosslinked car-boxymethyl cellulose versus linear CMC [350], The departure from the 1 1 stoichiometry with the non-neutralized microgels may be due to the collapsed nature of these networks which prevents penetration of water soluble polyelectrolyte. 

As discussed in the Introduction to this paper, different viscosity versus concentration behavior is observed for SFS solutions in toluene/methanol and in DMF. Folyelectrolyte behavior is observed only in the latter solvent. The ESR spectrum of a 2.65 mole % Mn-SPS in these two solvents was studied at various concentrations. For both lvents, the hyperfine structure characteristic of isolated Mn ions was observed in very dilute solutions and at concentrations for which Lundberg and Phillips(10) observed strong intermolecular interactions. The ESR data indlcat that in dilute solution in both DMF and toluene/methanol, the Mn exists mainly as Isolated cations. In addition, the IR spectra indicated that the cation is removed from the anion to a similar degree in both solvents. Yet, a polyelectrolyte effect is observed experimentally only in DMF solutions. Although there was some dipole-dipole broadening of the toluene/methanol spectrum, the line width and the g-factor (g 2,000) in both cases were ldent fal. The g-factor of 2.000 is characteristic of an isolated Mn in solution ). 

As discussed before, the borderline between polysoaps and polyelectrolytes or thickeners is determined by the hydrophilic-hydrophobic balance HLB, as well as by the length and the density of the hydrophobic tails chosen. The longer they are, the lower is the content of hydrophobic tails - the Critical Alkyl Group Content CAC [52, 75] - needed in order to produce polysoap behaviour (cf. Sect. 2.3.2). For poly(2-vinylpyridine) and poly(4-vinylpyridine), about 20% of derivatization with octyl tails and about 10% of derivatization with dodecyl tails are needed as a minimum to obtain the characteristic low viscosities [49, 52, 75, 133, 141, 317] (Fig. 17). Comparable CAC values are obtained for derivatized poly(vinyl-imidazol)s [140] and for poly(allylamine)s [152]. Similarly in anionic copolymers of poly(sodium 2-acrylamido-2-... 

In previous publications on the interaction between cationic polyelectrolytes and anionic surfactants, we have described the solu-bility, surface tension, electrophoresis, and dye solubilization characteristics of their mixtures. We also reported briefly on their viscosity behavior. ... 

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