Ionic polymer transducers (IPT) based on electroactive polymers (EAP) display electromechanical coupling that enables breakthroughs in the design of high-performance actuators and sensors. The ion-exchange membrane Nafion remains as the benchmark for a majority of research and development in IPT technology. Advances in IPT performance, elemental understanding of transduction mechanisms, and the development of future technologies (e.g., artificial muscles) are largely due to significant efforts to tailor complementary transducer compositions relative to commercially available Nation. Current fundamental advances in the synthesis, characterization, and application of tailored ion-containing polymers are reviewed for increased performance, decreased cost, and improved processing of IPTs. Recent attention to the correlation of morphological structure to ion conduction mechanisms has led to new paradigms for performance. Tailoring of ionomeric membranes to isolate material interactions within the composite IPT that contribute to performance is also highlighted. Novel compositions such as ion-containing polysulfones, poly(ethylene-co-vinyl alcohol), polystyrene, and fluorinated acrylic copolymers have broadened the range of electromechanical performance. This perspective discusses recent research efforts and rapidly emerging fundamental understanding of the tailored synthesis of ionomers for IPTs. However, further studies are necessary to confirm the mechanisms that drive these devices under an array of compositions and geometries in emerging applications.