Polyelectrolytes are polymers with dissociating groups in their repeat units. They can be divided into polycations and polyanions and polysalts. Like strange electrolytes (acids, bases and salts), they dissociate in aqueous options (water) and bear one or more costs depending on the pH value. Thus, the properties of polyelectrolytes are much like each electrolytes and polymers. The salts, i.e. the products of a polyacids (polyanions) with a monomeric base and vice versa are called polysalts. Like common salts, their options are electrically conductive and like polymers, their viscosity strongly relies on the molecular weight and polymer concentration.
The three commonest anionic groups are automobileboxylate (–COO-), phosphonate (–PO3H-, –PO32-), and sulfonate (–SO3-) and the most common cationic groups are main, secondary and quaternary ammonium (–NH3+, =NH2+ & ≡N+). The type of ionic group, its counter ion and the construction of the repeat unit decide the properties of a polyelectrolyte corresponding to solubility in water and different polar and hydrogen-bonding liquids (alcohols etc.), electrical conductivity, and solution viscosity. Unlike nonionic polymers, these properties strongly rely upon the pH and salt content.
Polyelectrolytes could be chemically crosslinked by incorporating a small amount of a suitable crosslinking agent. These polyelectrolytes kind three-dimensional constructions that swell in water reasonably than dissolving in it. They’ll retain (extremely) massive quantities of liquid relative to their own mass through hydrogen bonding with water molecules. They’re called hydrogels or superabsorbent polymers (SAP’s) when (slightly) cross-linked. Their ability to absorb water is a factor of the ionic concentration of the aqueous solution. In deionized and distilled water, SAPs could absorb water up to 500 times their own weight and from 30 to 60 times their own volume, that is, a hydrogel can encompass more than ninety nine% liquid. The total absorbency and swelling capacity of SAP’s is controlled by the type and amount of crosslinks within the structure.
Both natural and synthetic polyelectrolytes are manufactured on a large scale. Common natural polyelectrolytes are pectin (polygalacturonic acid), alginate (alginic acid), automotiveboxymethyl cellulose and polypeptides. Examples of common artificial polyelectrolytes are polyacrylic acid, polystyrene sulfonate, polyallylamine, automobileboxymethyl cellulose and their salts. A few of these polyelectrolytes are depicted beneath:
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