Polyelectrolyte complex solubility

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). 

Keywords Bio artificial pancreas, biomaterials, complex coacervation, immunoisolation, microencapsulation, polyelectrolytes, water soluble polymers. 

Significant research has been directed toward the use of polyelectrolyte complexes as blood compatible materials. Several investigators found that water-insoluble polyelectrolyte complexes can suppress blood coagulation [487-490]. Davison and coworkers reviewed and studied the biological properties of water-soluble polyelectrolyte complexes [491] between quatemized poly(vinyl imidazole) or polyvinyl pyridine) and excess sulfonated dextran or poly(methacrylic acid). By forming complexes with a stoichiometric excess of anionic charge, a more compact conformation with anionic character was obtained. 

Aggregates like polyelectrolyte complexes having positive charges and hydrophobic domains show a broader optimum flocculation concentration range and are considered as new reactive nanoparticles [11-14], Thus, polycations with hydrophobic functionalities represent an interesting class of water-soluble associating polyelectrolytes relevant for controlled stabilization/flocculation of dispersions in numerous industrial applications. 

The formation of polyelectrolyte complexes (PEC) is governed by the characteristics of the individual polyelectrolyte components (e.g. properties of ionic sites - strong or weak electrolyte -, position of ionic sites, charge density, rigidity of macromolecular chains) and the chemical environment (e.g. solvent, ionic strength, pH and temperature). Polyelectrolyte complexes are either separated from the solution as solids or liquids or they are still soluble in solution or may settle as gels due to variation of the controlling factors mentioned above. 

Izumrudov et al.145) reported non-equimolar water-soluble polyelectrolyte complexes composed of PMAA and quaternized poly(4-vinylpyridine) (poly(N-ethyl-4-vinylpyridinium bromide) QPVP). When the pH is increased after making the mixing ratio (expressed as the molar ratio of [QPVP]/ [PMAA]) equal to unity in the neutralization (a) of PMAA beyond a = 0.8, it is confirmed that an equimolar water-insoluble complex is formed. If the initial... 

Fig. 17 a, b. Solubility of polyelectrolyte complexes in ternary solvent systems at 30 °C. 

The formation of a water-soluble complex of poly(sodium acrylate) with 5,6 ionen bromide of 3 1 composition has been observed108. Its mass and size are independent of the complex origin and are equal to 660 x 103 and 33 nm respectively. The soluble complex presumably consists of the insoluble nucleus of the equimolar polyelectrolyte complex and adsorbed excess of poly(sodium acrylate) on its surface. The soluble polyelectrolyte complex dissociates at higher ionic strengths (0.05-0.1) whereas the insoluble equimolar complex in the core is still stable and precipitates from the solution. 

The water-insoluble PMAA-poly(N-ethyl-4-vinylpyridinium bromide)polyelectro-lyte complex (5 l) formed at pH < 4 becomes soluble if the excess PMAA in the polyelectrolyte complex is ionized110. The solubility of the polyelectrolyte complex is apparently connected with the appearance of high negative charges of the complex particles and is accompanied by a conformational transition of PMAA in excess. It has been proposed that the water-soluble polyelectrolyte complex consists of the nucleus formed by bound base and acid units. This structure is retained in solution due to unbound parts (sequences) of ionized PMAA. 

Davison, C.J. Smith, K.E. Hutchinson, L.E.F. O Mullane, J. Physical and biological properties of water soluble polyelectrolyte complexes. J. Bioact. Compat. Polym. 1990, 5 (3), 267-282. 

E. Ringenbach, G. Chauveteau and E. Pefferkom, Adsorption of polyelectrolytes on soluble oxides induced by polyion complexation with dissolution species. /. Colloid Interface Sci., 161 (1993) 223-231. 

WI Starch Xanthate. Research by Wing and others (22, 27-29) has shown that water-soluble (WS) starch xanthates, in combination with cationic polymers to form polyelectrolyte complexes, can effectively remove heavy metals from waste water. To eliminate the expensive cationic polymer and give a more economical method of heavy metal removal, further research by Wing and others (12,30-33) showed that xanthation of a highly crosslinked starch yields a water-insoluble (WI) product that is effective in removing heavy metals from waste water without the need for a cationic polymer. In more recent work, Tare and Chaudhari (34) evaluated the effectiveness of the starch xanthate (WS and WI) process for removal of hexavalent chromium from synthetic waste waters. 

Earlier work (9) has shown that the size of the precipitate, but not the protein recovery, depends on the method of addition of the polymer to the protein solution. Mixing conditions in the precipitation vessel also affect the precipitate size (lOh The solubility of the protein-polyelectrolyte complex depends strongly on the solution conditions—pH, ionic strength, polymer dosage level, and the nature of the protein and polyelectrolyte. These factors are discussed below ... 

Xia J., Dubin P. L., Kim Y., Muhoberac B. B., Klimkowski V. J. Electrophoretic and quasi-elastic light scattering of soluble protein-polyelectrolyte complexes. J. Phys. Chem. 1993 97 4528-4534. 

Zezin AB, Kabanov VA. New form of the polyelectrolytes water-soluble complexes. Usp Khim 1982 51(9) 1447-1483. 

Pergushov DV, Izumrudov VA, Zezin AB, Kabanov VA. Effect of low-molecular-mass salts on the behavior of water-soluble nonstoichiometric polyelectrolyte complexes. Polymer Science, Ser A 1993 35(7) 844-849. 

Karibyants N, Dautzenberg H. Preferential binding with regard to chain length and chemical structure in the reactions of formation of quasi-soluble polyelectrolyte complexes. Langmuir 1998 14 4427-4434. 

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