Polyelectrolytes are polymers with dissociating teams of their repeat units. They can be divided into polycations and polyanions and polysalts. Like abnormal electrolytes (acids, bases and salts), they dissociate in aqueous solutions (water) and bear one or more charges relying on the pH value. Thus, the properties of polyelectrolytes are just like both electrolytes and polymers. The salts, i.e. the products of a polyacids (polyanions) with a monomeric base and vice versa are called polysalts. Like regular salts, their options are electrically conductive and like polymers, their viscosity strongly is determined by the molecular weight and polymer concentration.
The three most typical anionic teams are automotiveboxylate (–COO-), phosphonate (–PO3H-, –PO32-), and sulfonate (–SO3-) and the commonest cationic groups are primary, secondary and quaternary ammonium (–NH3+, =NH2+ & ≡N+). The type of ionic group, its counter ion and the construction of the repeat unit determine the properties of a polyelectrolyte resembling 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 can be chemically crosslinked by incorporating a small amount of a suitable crosslinking agent. These polyelectrolytes form three-dimensional constructions that swell in water slightly than dissolving in it. They can retain (extremely) massive amounts 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 soak up water is a factor of the ionic concentration of the aqueous solution. In deionized and distilled water, SAPs may take up water up to 500 occasions their own weight and from 30 to 60 occasions their own quantity, that’s, a hydrogel can encompass more than ninety nine% liquid. The total absorbency and swelling capacity of SAP’s is managed by the type and quantity of crosslinks within the structure.
Both natural and synthetic polyelectrolytes are manufactured on a large scale. Widespread natural polyelectrolytes are pectin (polygalacturonic acid), alginate (alginic acid), carboxymethyl cellulose and polypeptides. Examples of common synthetic polyelectrolytes are polyacrylic acid, polystyrene sulfonate, polyallylamine, carboxymethyl cellulose and their salts. Some of these polyelectrolytes are depicted beneath:
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