  Polyelectrolyte gels are a very attractive class of actuation materials with
remarkable electronic and mechanical properties with a great similarity to
biological contractile tissues. They consist of a polymer network with
ionizable groups and a liquid phase with mobile ions. Absorption and delivery
of solvent lead to a large change of volume. This mechanism can be triggered by
chemical (change of salt concentration or pH of solution surrounding the gel),
electrical, thermal or optical stimuli. Due to this capability, these gels can
be used as actuators for technical applications, where large swelling and
shrinkage is desired. In the present work chemically stimulated polymer gels in
a solution bath are investigated. To adequately describe the different
complicated phenomena occurring in these gels, they can be modeled on different
scales. Therefore, models based on the statistical theory and porous media
theory, as well as a coupled multi-field model and a discrete element
formulation are derived and employed. In this paper, the coupled multi-field
model and the discrete element model for chemical stimulation of a polymer gel
film with and without domain deformation are employed. Based on these results,
the presented formulations are compared and conclusions on their applicability
in engineering practice are finally drawn.
