Properties of Polyelectrolytes
Polyelectrolytes are polymers with dissociating teams in their repeat units. They are often divided into polycations and polyanions and polysalts. Like bizarre electrolytes (acids, bases and salts), they dissociate in aqueous solutions (water) and bear one or more fees relying on the pH value. Thus, the properties of polyelectrolytes are much 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 common salts, their solutions are electrically conductive and like polymers, their viscosity strongly depends upon the molecular weight and polymer concentration.
The three commonest anionic groups are carboxylate (–COO-), phosphonate (–PO3H-, –PO32-), and sulfonate (–SO3-) and the most common cationic groups are major, 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 comparable to solubility in water and different polar and hydrogen-bonding liquids (alcohols etc.), electrical conductivity, and answer viscosity. Unlike nonionic polymers, these properties strongly depend on 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 structures that swell in water fairly than dissolving in it. They'll retain (extraordinarily) massive quantities of liquid relative to their own mass through hydrogen bonding with water molecules. They are 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 as much as 500 times their own weight and from 30 to 60 times their own quantity, that is, a hydrogel can encompass more than 99% liquid. The total absorbency and swelling capacity of SAP’s is controlled by the type and amount of crosslinks in the structure.
Both natural and synthetic polyelectrolytes are manufactured on a big scale. Common natural polyelectrolytes are pectin (polygalacturonic acid), alginate (alginic acid), carboxymethyl cellulose and polypeptides. Examples of frequent synthetic polyelectrolytes are polyacrylic acid, polystyrene sulfonate, polyallylamine, automobileboxymethyl cellulose and their salts. A few of these polyelectrolytes are depicted under:
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