By complexing metal ions into the polymer matrix, the strength and toughness of the ionomer system is increased. Some applications where ionomers were used to increase the toughness of the overall system include coatings, adhesives, impact modification, and thermoplastics, one of the most known examples being the use of Surlyn in the outer layer of golf balls. The ionomer coating improves the toughness, aerodynamics, and durability of the golf balls, increasing their lifetime. Ionomers can also be blended with resins to increase the cohesive strength without diminishing the overall tackiness of the resin, creating pressure sensitive adhesives for a variety of applications, including water or solvent-based adhesives. Ionomers using poly(ethylene-methacrylic acid) chains can also be used in film packaging due to their transparency, toughness, flexibility, resistance to staining, high gas permeability, and low sealing temperature. These qualities also translate to a high demand for using the ionomers in food-packing materials.
With the addition of the ion to a certain percentage of the polymer chain, the viscosity of the ionomer increases. This behavior can make ionomers a good viscosification material for drilling fluid applications where the system is under a low shear rate. Using the ionomer to increase the viscosity of the system helps prevent shear thinning behaviors within the drilling fluid, especially at higher temperatures of operation.
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.
Some more recent applications for ionomers include being used as ion-selective membranes in a variety of electrical and energy applications. Examples include the cation exchange membrane for fuel cells, which allow only protons or specific ions to cross the membrane, a polymer electrolyte membrane (PEM) water electrolyzer to optimize the uniform coating of the catalyst on membrane surfaces, a redox flow battery separator, electrodialysis, where ions are transported between solutions using the ionomer membrane, and electrochemical hydrogen compressors to increase the strength of the membrane against the pressure differentials that can occur within the compressor.