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

The swelling of polyelectrolyte gels in water and salt solutions is associa ted with the presence of up to three coexisting phases: a dry phase, a swol len 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 si ze, and a further swelling that scales linearly with the initial gel size. We show that there exist various swelling paths depending on the gel intera ction with metal ions and their concentration.