Swelling kinetics of a polyelectrolyte gel in water and salt solutions. Coexistence of swollen and collapsed phases

Abstract : The swelling of polyelectrolyte gels in water and salt solutions is associated with the presence of up to three coexisting phases: a dry phase, a swollen phase, and a collapsed one due to the binding of metal ions to polyions. Swelling in pure water proceeds in two ways: a transition from the dry to swollen state, whose kinetics scales with the square of the initial gel size, and a further swelling that scales linearly with the initial gel size. We show that there exist various swelling paths depending on the gel interaction with metal ions and their concentration.