Polyelectrolyte

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polyelectrolyte

[¦päl·ē·ə′lek·trə‚līt]
(organic chemistry)
A natural or synthetic electrolyte with high molecular weight, such as proteins, polysaccharides, and alkyl addition products of polyvinyl pyridine; can be a weak or strong electrolyte; when dissociated in solution, it does not give uniform distribution of positive and negative ions (the ions of one sign are bound to the polymer chain while the ions of the other sign diffuse through the solution).

Polyelectrolyte

 

a polymer electrolyte, that is, a polymer that dissociates into ions in solution. A large number of periodically repeating charges arises in each macromolecule during dissociation. Polyelectrolytes are divided into polyacids (for example, polyacrylic acids), polybases (such as polyvinyl pyridinium), and polyampholytes (copolymers containing both basic and acidic groups). Most polyelectrolytes contain weak acidic or basic groups and therefore are ionized only in the presence of a strong base (for a polyacid) or strong acid (for a polybase).

Primary biopolymers such as proteins and nucleic acids are among the polyelectrolytes. Cross-linked polyelectrolytes, which are prepared by the introduction of readily dissociating groups (for example, sulfo and amino groups) into various cross-linked polymers, are of great importance to industry and laboratory practice. The most valuable cross-linked polyelectrolytes are ion-exchange resins.

The dissociating groups in the polymer molecules determine the solubility of polyelectrolytes in water and other polar liquids. For example, a sulfonated linear polystyrene dissolves freely in water, although polystyrene itself is one of the most water-resistant polymers known. Cross-linked polyelectrolytes of three-dimensional structure swell in water rather than dissolving. The properties of polyelectrolyte molecules in solution are determined by the electrostatic interaction of charged groups in the chain with one another and with low-molecular-weight ions in the solution. The strong electrostatic field generated by the charges in the polyelectrolyte molecule holds a large number of oppositely charged ions close to the molecule. The electrostatic repulsion of groups of like charge leads to a substantial alteration of the macromolecular conformations in solutions: the effective size of the molecules increases, and the coiled chains straighten out, assuming an approximately linear form as the degree of polyelectrolyte dissociation increases. The physicochemical properties of solutions also undergo considerable alteration (for example, solution viscosity increases by hundreds and thousands; the higher the concentration, the greater the viscosity). The theory that was developed for solutions of low-molecular-weight electrolytes ceases to be valid for polyelectrolyte solutions. The low-molecular-weight ions that appear during the dissociation of polar groups of these polyelectrolytes create a diffuse shell around the oppositely charged surface of the polymer and may to some degree be replaced by other ions of like sign.

REFERENCES

Tager, A. A. Fiziko-khimiia polimerov, 2nd ed. Moscow, 1968.
Rice, S. A., and M. Nagasawa. Polyelectrolyte Solutions: A Theoretical Introduction. London-New York, 1961.

M. E. ERLYKINA

References in periodicals archive ?
Surfaces that need to possess specific properties, such as antimicrobial surfaces or antithrombogenic surfaces, or those with decreased cell adhesion or enhanced cell adhesion can be constructed by the employing the appropriate combination of polyelectrolytes.
As to PAN fibers, due to small diameters, leading to a small pore sizes of nanofibrous mats, which make them used as middle layer, helpful to avoid too much polyelectrolytes penetrating into nanofibrous substrate, resulting in a serious pore blocking [31].
Alhydrogel (360 [micro]l) was added drop wise to a solution of the polyelectrolyte (40 [micro]l) upon vortexing and the system incubated for 10 min.
Ho, Spatially Controlled Cell Engineering on Biomaterials Using Polyelectrolytes.
Going a step further in another project, Halaoui has created films with layers of polyelectrolytes and layers hosting quantum dots and platinum nanoparticles that can catalyze the production of hydrogen gas from water.
These features are similar to those associated with DNA condensation and can be explained analogously by polyelectrolyte theory (Tang and Janmey, 1996; Tang et al.
18 Polyelectrolytes At Interfaces: Applications And Transport Properties Of Polyelectrolyte Multilayers In Membranes
Ballouf, Polyelectrolytes with Defined Molecular Architecture, Springer-Verlog, Berlin (2004).
Schlenoff suggests that manufacturers could inexpensively line pipes with anticorrosive multilayers by alternately pumping solutions of oppositely charge polyelectrolytes through the pipes before they're used.
Butler's cyclopolymerization protocol has led to the synthesis of a variety of cationic and anionic polyelectrolytes (1) as well as polybetaines (having charges of both algebraic signs in the same repeating units) (2-6) and polyampholytes (having repeating units containing cationic and anionic charges with or without charge symmetry) (7).