Polyelectrolytes are a class of polymer whose swelling depends on the external condition of pH. The dissociation of the ionizable groups is strongly depended on the concentration of the H+ ions in solution and this leads to different swelling behaviour changing the external pH. Since these materials are versatile and used in various fields, an in-depth knowledge of their behaviour becomes important to use them appropriately. The present work aims to offer an overview of the behaviour of these materials in solution through an experimental and a steady state modelling part. The results serve as a fundamental basis to understand the behaviour of these systems, including transient periods, leading to a comprehensive and predictable description.