Polyelectrolytes complexes

Oppositely charged polyelectrolytes interact with each other to form polyelectrolyte complexes in solution, the possible combinations including strong poly-acids-strong polybases, strong polyadds-weak polybases, weak polyadds-strong polybases, weak polyadds-weak polybases, or polyampholytes. Consid- 

Studies on the interaction between oppositely charged polyelectrolytes date back to 1896 when Kossel389 precipitated egg albumin with protamine. Since that time extensive studies have been made on pairs of strong polyelectrolytes, pairs of strong and weak polyelectrolytes, pairs of weak polyelectrolytes, as well as on amphoteric complexes. However, the theoretical considerations of intermacromolecular interactions between polyelectrolytes were only based on extremely simplified model systems. However, even in the case of such systems, there are many unsolved problems such as the determination of the local dielectric constant in domains of macromolecular chains, the evaluation of other secondary binding forces, especially hydrophobic interactions, and so on. 

Oosawa390 described a very simple theory based on the electric free energy to claculate the repulsive forces between parallel rod-like macoions in solution as a function of the charge density on the rods. The total extensive force 

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. 

On the other hand, when integral-type polycations (having cationic charges on the backbone chain) instead of pendant-type polycations, are used as strong polybases, different phenomena are observed. Tsuchida et al.m) discussed the interactions between NaSS and a series of integral-type polycations, called ionenes  

One of the reasons why poly(3,4-ethylenedioxythiophene) (FEDOT) has become a successful conductive polymer is the availability as a polymer dispersion. In combination with poly(styrenesulfonic acid) (PSS) as a counterion, a polyelectrolyte complex (PEC) can be prepared that forms a stable dispersion, which is producible on an industrial scale and can be used in many deposition techniques. To understand the function of PSS and the requirements for the formation of a stable PEC, this chapter will start with a general view on polyelectrolyte complexes. This is followed by a section on the synthesis and properties of PEDOT PSS dispersions, the properties of PEDOTPSS films, and the function of conductivity enhancement agents. 

PEC arrangements (left) ladder-type and (right) scrambled egg type. (Adapted from B. Philipp, W. Dawydoff, and K.-J. Linow, 1982, Z Chem 22(1) 1-13 H.-G. Elias, 2001, Makromolekiile 

The solvent used for most PECs described in literature is water, since it dissolves polyelectrolytes well due to its high dielectric constant furthermore, it is easily accessible, nontoxic, and therefore the natural solvent for polyelectrolytes.i To assess the stability of a PEC, it is necessary to consider 

The mixing of solutions containing stoichiometric amounts of polyanions and polycations, which can be described in the equation [Cp s] otpos= [Cpeg] otneg, generally leads to the precipitation of both species. This is due to the fact that the polar groups screen each other and the overall solubility is lost. Only at very low concentrations a few cases of soluble complexes with stoichiometric amounts of polyanions and polycations have been demonstrated, for example, in the case of poly(styrenesulfonate) and Polybrene (1,5-dimethyl-1,5-diazaundecamethylene polymethobromide hexadimethrine bromide).  

However, when polyanions and polycations are mixed in nonstoichiometric ratios, soluble complexes can be formed. These polyelectrolyte complexes are found in the form of discrete soluble gel particles in the aqueous medium. For nonstoichiometric polyelectrolyte complexes the major component can also be described as host polyelectrolyte (HPE), whereas the oppositely charged minor component can be described as guest polyelectrolyte (GPE). The latter joins the repeat units of the HPE via electrostatic interactions, so that a network is formed. Eor the formation of soluble particles, it is beneficial if the HPE consists of high molecular weight material, whereas the GPE has a low molecular weight. Eurthermore, it is beneficial for a stable PEC if at least one of the polyelectrolytes has weak ionic groups. 

In another example, a hydrophilic star block copolymer was composed of a hyperbranched PEI core, a PLL inner shell and a PEG outer shell. Insulin, as a model protein, can be rapidly and efficiently encapsulated by the synthesized polymer in aqueous phosphate buffer at physiological pH. Complexation between PEI-PLL-Z)-PEG and insulin was demonstrated using native polyacrylamide gel electrophoresis. An in vitro release study by dialysis showed sustained release of the encapsulated protein at physiological pH, and an accelerated release when the pH was decreased. The insulin released from the star block copolymer retained its chemical integrity and immu-nogenicity. Successful in vitro uptake studies of enhanced green fluorescent protein into Ad293 cells mediated by PEI-PLL-Z)-PEG were also performed.  

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Polyelectrolyte complex membranes are phase-inversion membranes where polymeric anions and cations react during the gelation. The reaction is suppressed before gelation by incorporating low molecular weight electrolytes or counterions in the solvent system. Both neutral and charged membranes are formed in this manner (14,15). These membranes have not been exploited commercially because of then lack of resistance to chemicals. 

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). 

A variety of synthetic polymers, including polycarbonate resins, substituted olefins, and polyelectrolyte complexes, are employed as ultrafiltration membranes. Many of these membranes can be handled dry, have superior organic solvent resistance, and are less sensitive to temperature and pH than cellulose acetate, which is widely used in RO systems. 

Keywords Chitosan Nanoparticles Microspheres Chemically modified chitosans Polyelectrolyte complexes Oral and nasal administration Nerve, cartilage and bone regeneration Wound dressing... 

Polyelectrolyte complexes composed of various weight ratios of chitosan and hyaluronic acid were found to swell rapidly, reaching equilibrium within 30 min, and exhibited relatively high swelling ratios of 250-325% at room temperature. The swelling ratio increased when the pH of the buffer was below pH 6, as a result of the dissociation of the ionic bonds, and with increments of temperature. Therefore, the swelling ratios of the films were pH-and temperature-dependent. The amount of free water in the complex films increased with increasing chitosan content up to 64% free water, with an additional bound-water content of over 12% [29]. 

A simple example of gel formation is provided by chitosan tripolyphosphate and chitosan polyphosphate gel beads the pH-responsive swelling abihty, drug-release characteristics, and morphology of the gel bead depend on polyelectrolyte complexation mechanism and the molecular weight. The chitosan beads gelled in pentasodium tripolyphosphate or polyphosphoric acid solution by ionotropic cross-hnking or interpolymer complexation, respectively. 

The chitosan-heparin polyelectrolyte complex was covalently immobilized onto the surface of polyacrylonitrile membrane. The immobilization caused the water contact angle to decrease, thereby indicating an increase in hy-... 

For the preparation of spray-dried polyelectrolyte complexes, the polyanion was dissolved in dilute NH4HCO3 solution and mixed with the chitosan carbamate solution just before spray-drying. The excess NH4HCO3 decomposed thermally between 60 and 107 °C on the other hand, the carbamate function released carbon dioxide under the effect of the temperature at which the spray-drier was operated, thus regenerating chitosan at the moment of the polyelectrolyte microsphere formation (Fig. 5). 

Fig. 5 Microspheres manufactured from the polyelectrolyte complex of chitosan carbamate and ammonium alginate in ammonium bicarbonate solution. Muzzarelli, original data, 2004...

Gregor, H. P., Luttinger, L. B. Loebl, E. M. (1955b). Metal-polyelectrolyte complexes. IV. Complexes of polyacrylic acid with magnesium, calcium, cobalt and zinc. Journal of Physical Chemistry, 59, 990-1. 

B Phillip, H Dautzenber, KJ Linow, J Kotz, W Dawydoff. Polyelectrolyte complexes—Recent developments and open problems. Prog Polym Sci 14 91-172, 1989. 

Counterion gel 4- —> swelling 4- (Exception polyelectrolyte complexes) Effect depends on species salting-in/salting-... 

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. 

Reihs T, Muller M, Lunkwitz K (2004) Preparation and adsorption of refined polyelectrolyte complex nanoparticles. J Colloid Interface Sci 271 69-79... 

Kang HS, Park SH, Lee YG et al (2007) Polyelectrolyte complex hydrogel composed of chitosan and poly(y-glutamic acid) for biological application Preparation, physical properties, and cytocompatibility. J Appl Polym Sci 103 386-394... 

Muller M, Reihs T, Ouyang W (2005) Needlelike and spherical polyelectrolyte complex nanoparticles of poly(L-lysine) and copolymers of maleic acid. Langmuir 21 465 -69... 

Hartig SM, Greene RR, DasGupta J et al (2007) Multifunctional nanoparticulate polyelectrolyte complexes. Pharm Res 24 2353-2369... 

Polymer Attributes to Be Considered in Capsule Formation via Polyelectrolyte Complexation... 

Cationic ions and polyelectrolytes can stabilize the formation of the PS I monolayers at the air-water interface. These complex monolayers can be transferred onto the hydrophobic substrate surfaces by horizontal lifting method. The PS I/polyelectrolyte complex film may be used for the development of a biosystem for the studies on photoinduced electron transfer and for hydrogen evolution. 

KPVS) and the indicator is usually o-toluidine blue (OTB). It is necessary for kx to be much larger than k2 (which is usually the case for poly electrolytes). If for example a cationic poly electrolyte together with OTB is titrated with KPVS, a polyelectrolyte complex is initially formed until no free polyelectrolyte is left to react with the KPVS. At this point, KPVS starts to react with OTB and a colour shift from light-blue to purplish-red indicates the end point. The titration relies upon the formation of a 1 1 complex, which is generally true provided that the ionic strength is low. 

Wang D, Gong X, Heeger PS, Rininsland F, Bazan GC, Heeger AJ (2002) Biosensors from conjugated polyelectrolyte complexes. Proc Natl Acad Sci 99 49-53... 

Wolfert MA, Seymour LW. Atomic force microscopic analysis of the influence of the molecular weight of poly(L)lysine on the size of polyelectrolyte complexes formed with DNA. Gene Ther 1998 3(3) 269-273. 

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