Formation of polyelectrolyte complexes

It should be pointed out that the addition of substances, which could improve the biocompatibility of sol-gel processing and the functional characteristics of the silica matrix, is practiced rather widely. Polyethylene glycol) is one of such additives [110— 113]. Enzyme stabilization was favored by formation of polyelectrolyte complexes with polymers. For example, an increase in the lactate oxidase and glycolate oxidase activity and lifetime took place when they were combined with poly(N-vinylimida-zole) and poly(ethyleneimine), respectively, prior to their immobilization [87,114]. To improve the functional efficiency of entrapped horseradish peroxidase, a graft copolymer of polyvinylimidazole and polyvinylpyridine was added [115,116]. As shown in Refs. [117,118], the denaturation of calcium-binding proteins, cod III parvalbumin and oncomodulin, in the course of sol-gel processing could be decreased by complexation with calcium cations. 

Polyelectrolyte complexes are formed by the ionic association of two oppositely charged polyelectrolytes [60,117-119]. Due to the long-chain structure of the polymers, once one pair of repeating units has formed an ionic bond, many other units may associate without a significant loss of translational degree of freedom. Therefore the complexation process is cooperative, enhancing the stability of the polymeric complex. The formation of polyelectrolyte complexes... 

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. 

Fig. 5. Schematic representation of the effect of the position of cationic sites of polycations on the formation of polyelectrolyte complexes...

Fig. 6 a, b. Acceleration of dissociation of poly(carboxylic acid)s according to the complex formation with various polycations, (a) Potentiometric titration of poly(methacrylic add) (PMAA) and its complexes (b) Amount of protons released from poly(carboxy]ic add) in the formation of polyelectrolyte complexes. Polyanions PMAA and poly(acrylic add) (PAA). Polycations and their low molecular weight analogues ... 

Up to now, the effects of the characteristics of the polyelectrolyte components themselves have been discussed. The effect of the reaction conditions, for example ionic strength, solvent, concentration and temperature on the formation of polyelectrolyte complexes will also be discussed in detail. When increasing the ionic strength, the following phenomena are expected to be observed ... 

Fig, 12 a, b. Effect of ionic strength on the formation of polyelectrolyte complexes (a) Reduced viscosity, (b) transmittance Poly(methacrylic acid) (PMAA) (degree of neutralization of PMAA a = l)-Ionene-type polycation (2X), O PMAA(a = 0.75)-2X, 3 PMAA(a = 0.5)-2X, Poly(acrylic acid) (tz = 1)-2X, A Poly(sodium styrenesulfonate)-2X... 

Bakeev KN, Izumrudov VA, Kabanov VA. Kinetics and mechanism of reactions of the formation of polyelectrolytic complexes. Doklad Akad Nauk SSSR 1988 299 1405-1408. 

Deng SM, Li X. Formation of polyelectrolyte complexes based on pendant-type imidazolinium organosilicon polymer with poly(sodium acrylate). J Macromol Sci Pure Appl Chem 1997 A34(4) 695-704. 

Tsuchida, E. Formation of polyelectrolyte complexes and their structures. J. Macromol. Sci. Pure Appl. Chem. 1994, 31 (1), 1-15. 

Liu, Y.-J., and Kanatzidis, M. G., Postintercalative polymerization of aniline and its derivatives in layered metal phosphates, Chem. Mater., 7, 1525-1533 (1995). Tsuchida, E., Formation of polyelectrolyte complexes and their structures, J. M. S. Pure... 

Strom G, Barla P, Stenins P (1985) The formation of polyelectrolyte complexes between pine xylan and cationic polymers. Colloids Surf 13 193-207... 

Fig. 13.14 Formation of polyelectrolyte complex with ionic interaction and hydrogen bonding...

Fig. 4 Formation of polyelectrolyte complex micelles self-assembled from ODN-PEG conjugate and the peptide KALA [78] (figure reproduced with permission of American Chemical Society)...

Fig. 12.5. Change of the stabihty constant (K) and the free energy ( — d F in the formation of polyelectrolyte complexes with various degree of polymerization of oligo-cation. M (PMAA) = 5.3 x 10" ...

Over the last years, there has been a growing interest in PECs based on natural and synthetic polymers. Chitosan is a natural polyaminosaccharide and a weak base. Its PECs with different natural and synthetic polyacids such as, carboxy-methylcellulose [29, 30], alginic acid [23], poly (acrylic acid) [31] are known. Besides alginate, carboxymethylcellulose, carrageenan, and dextran sulfate are the most extensively studied polysaccharides used in the formation of polyelectrolyte complexes [32, 33]. Some synthetic polyelectrolytes, like poly(l-lysine) and polyacrylates, have been used to make complexes with these polysaccharides [34]. In the above mentioned literature one can find different examples of PEC as well as various methods of forming them. 

Mixing oppositely charged polyelectrolytes leads to the spontaneous formation of polyelectrolyte complexes concomitant with the release of counterions (Fig. la-c). As a first approximation, such a polyelectrolyte complexation may be described as a counterion exchange reaction in a system of polyanions (PA), polycations (PC), counterions (c", c ) and solvent [23, 24], according to ... 

Colloids can be also obtained by formation of polyelectrolyte complexes of a polyanion and a polycation as reported for synthetic (Buchhammer etaL, 2003) and natural polymers (Cui Mumper, 2001). 

The formation of polyelectrolyte complexes being known as mixing condition-dependent, the order of addition of the components ofpolycation-medium-RBC suspensions was modified. For the experiments reported so far, the polycation was added to whole blood or to RBC already suspended in the selected suspension medium. At the present point, selected polycations, namely (Q-P(TDAE)n, 19 and 124 kDa PLL and DEAE-dextran, were added to two of the previous suspension media, namely plasma and albumin buffer, prior to RBC, the final concentration in polycation being 10 mM. 

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