Swelling and Collapse of Physical Gels Formed by Associating Telechelic Polyelectrolytes

A theory is proposed for the swelling and collapse of physical gels formed by associating telechelic polyelectrolytes. It is shown that increasing the of degree of ionization makes the formation of an associative gel less favorable and increases the density of the supernatant phase. This leads to the contraction of the associative gel, in comparison with an analogous chemically cross-linked gel. The results of calculation show that the destruction of the associative gel happens monotonically in good solvent, while in poor solvent it can proceed in a jump-like fashion accompanied by the first-order phase decollapse transition of the associative gel. The addition of a low molecular weight salt to the solution facilitates the association of telechelic molecules which produces the associative gel and a further increase of salt concentration leads to the contraction of the associative gel.