Editing Polyelectrolyte (section)

== Charge ==

[[Acid]]s are classified as either [[weak acid|weak]] or [[strong acid|strong]] (and [[Base (chemistry)|bases]] similarly may be either [[weak base|weak]] or [[strong base|strong]]). Similarly, polyelectrolytes can be divided into "weak" and "strong" types. A "strong" polyelectrolyte dissociates completely in solution for most reasonable [[pH]] values. A "weak" polyelectrolyte, by contrast, has a [[dissociation constant]] (pKa or pKb) in the range of ~2 to ~10, meaning that it will be partially dissociated at intermediate pH. Thus, weak polyelectrolytes are not fully charged in the solution, and moreover, their fractional charge can be modified by changing the solution pH, counter-ion concentration, or ionic strength.

The physical properties of polyelectrolyte solutions are usually strongly affected by this degree of ionization. Since the polyelectrolyte dissociation releases counter-ions, this necessarily affects the solution's [[ionic strength]], and therefore the [[Debye length]]. This, in turn, affects other properties, such as [[Conductivity (electrolytic)|electrical conductivity]].

When solutions of two oppositely charged polymers (that is, a solution of '''polycation''' and one of '''polyanion''') are mixed, a bulk complex ([[precipitate]]) is usually formed. This occurs because the oppositely-charged polymers attract one another and bind together.