Summary: To develop ionic polymer‐metal composites (IPMC) with improved performance, three new ion‐exchange membranes were prepared and employed in IPMC construction. The membranes were prepared by radiation‐grafting of polystyrene sulfonic acid onto three fluoropolymers; poly(vinylidenefluoride‐co‐hexafluoropropylene), poly(ethylene‐co‐tetrafluoroethylene), and poly(tetrafluoroethylene‐co‐hexafluoropropylene). The bending displacements of the IPMCs constructed with these membranes were at least several times larger than that of Nafion IPMC of similar thickness without straightening‐back. The larger displacement was considered to be due to the higher concentration of ionic groups and consequent larger ion‐exchange capacity.Actuation of (a) Nafion IPMC and (b) IPMC prepared in this study.imageActuation of (a) Nafion IPMC and (b) IPMC prepared in this study.

On purpose to develop a polymer actuator with high stability in air-operation as well as large bending displacement, a series of ionic polymer-metal composites (IPMC) was constructed with poly(styrene sulfonate)-grafted fluoropolymers as ionomeric matrix and immidazolium-based ionic liquids (IL) as inner solvent. The prepared IPMC actuators exhibited greatly enhanced bending displacement compared to Nafion-based actuators. The actuators were stable in air-operation, maintaining initial displacement for up to 10(4) cycles or 24 h. Investigating the material parameters and morphology of the IPMCs, high ion exchange capacity of the ionomers resulted in high ion conductivity and robust electrode of IPMC, which synergistically contributed to the high bending performance.

Ionic polymer metal composites (IPMCs) are an emerging class of electroactive polymers (EAP), which have many potential applications as sensors and actuators. Recently, IPMCs have been intensively studied because of their huge potential in medical, mechanical, electronic, and aerospace engineering. However, before the benefits of these materials can be effectively exploited for practical use, a mathematical model must be established to enhance understanding and predictability of IPMC actuation. The coupled electrical-chemical-mechanical response of an IPMC depends on the structure of the polyelectrolyte membrane, the morphology and conductivity of the metal electrodes, the cation properties, and the level of hydration. With this in mind, the purpose of this study is to establish a finite element model for bending behavior of IPMC beams. With reference to their operation principle, it is assumed that an IPMC beam has three virtual layers. We draw an analogy between thermal strain and real strain in IPMC due to volume change. This is a coupled structure/thermal model, and the finite element method is used to solve this model. The ion concentration distribution in the IPMC boundary layer is mimicked with the temperature distribution, and the electromechanical coupling coefficient is mimicked with the thermal expansion coefficient. Theoretical and experimental results demonstrate that our suggested model is practical and effective enough in predicting the blocking force of IPMC strips for different input voltages and strip thicknesses.

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To develop a high-performance ionic polymer-metal composite (IPMC) actuator, a series of poly(styrene sulfonate)-grafted poly(ethylene-co-tetrafluoroethylene) (ETS) membranes with ion exchange capacity (IEC) ranging from 2.16 to 3.01 meq/g was synthesized by γ-radiation grafting. The degree of grafting and the IEC of the ETS were regulated by adjusting the grafting conditions, such as the total irradiation dose and polymerization time. The bending displacement and generating force of the actuators assembled with the ETS membranes increased monotonically in proportion to the IEC. All the prepared actuators exhibited much larger displacement and a faster response than those of the Nafion-based actuators without straightening-back. The excellent performance of the actuators was attributed to the inherent high IEC of the ETS and the consequent high number of available mobile cations and free water molecules in the ETS, leading to large volume expansion on the cathode side. Improved morphological and electrical properties of the platinum layer on the ETS as well as the high bending flexibility of the actuators also contributed to the increase in actuation performance.