Another application includes the ability of an ionomer to increase the compatibility of polymer blends. This phenomenon is driven by thermodynamics and is achieved through the introduction of specific interactions between functional groups that are increasingly favorable in the presence of a metal ion. The miscibility can be driven not only by the increasingly favorable reaction between functional groups on two different polymers but also by having a strong repulsive interaction between the neutral and ionic species present within an ionomer, which can drive one of these species to be more miscible with the species of the other polymer within the blend. Some ionomers have been used for shape memory applications, meaning the material has a fixed shape that can be reformed using external stresses above a critical temperature and cooled, then regains the original shape when brought above the critical temperature and allowed to cool under no external stresses. Ionomers can form both chemical and physical crosslinks that can be modified easily at moderate processing temperatures, are less dense than shape memory alloys, and have a higher chance of being biocompatible for biomedical devices.