Abstract:Conventional shape memory polymers suffer the drawbacks of low thermal stability, low strength, and low shape recovery speed. In this study, main-chain liquid crystalline polyurethane (LCPU) that contains polar groups was synthesized. Graphene oxide (GO)/LCPU composite was fabricated using the solution casting method. The tensile strength of GO/LCPU was 1.78 times that of neat LCPU. In addition, shape recovery speed was extensively improved. The average recovery rate of sample with 20 wt % GO loading was 9.2˝/s, much faster than that of LCPU of 2.6˝/s. The enhancement in mechanical property and shape memory behavior could be attributed to the structure of LCPU and GO, which enhanced the interfacial interactions between GO and LCPU.
composite (IPMC) actuators had attracted much attention from both scientists and engineers for it was considered as a good candidate for robotic actuators, artificial muscle, and dynamic sensors. IPMC had several outstanding advantages including flexibility, low power consumption, high energy density, and a large displacement under a low voltage. [3,4] Typically, an IPMC composed of an ionexchanging polymer film sandwiched by two electrodes which were frequently made of noble metals. Driven by an electrical field, the IPMC actuator would provide a bend deformation, for the hydrated metal cations inside the film migrated toward the cathode. However, there were two major drawbacks concerning the conventional IPMC actuators. The first was the poor durability under longterm actuation in open air because of the back-diffusion of cationic clusters and evaporation of solvent through cracks in the metallic electrodes. The second was the complicated and time-consuming fabricating of the metallic electrodes, usually including sand blasting, ion absorption, primary and secondary plating, and ion exchange. [5] Therefore, improving the durability of IPMC actuators and simplifying the fabrication of electrodes constituted the main challenges in the field of IPMC actuators.A facile method to fabricate ionic polymer-metal composite (IPMC) actuators is proposed. A blend of mesoporous graphene (MG) and Nafion is used as the ionic matrix, which is sandwiched by two layers of blend of reduced graphene oxide (rGO) and Nafion as the electrodes. When subjected to an electrical field of 3 V, the IPMC actuator exhibits a blocking force of 10 gf g −1 for 20 s, and the same behavior can be repeatedly played for hundreds of cycles. MG improves the mechanical properties of Nafion-based IPMC, more importantly, the mesopores in graphene provide additional pathway for the diffusion of cationic clusters and thus enhance the actuation speed. In addition, the surface electrodes of rGO protect the interlamellar liquid from evaporation thus ensure the durability.
Conventional ionic polymer-metal composite actuator had two major drawbacks: (i) complicated and time-consuming fabrication of noble metal electrode and (ii) degradation of electromechanical property in open air.In this study, we proposed a facile method to fabricate graphene oxide (GO)-based electromechanical actuators with surface-reduced graphene oxide (rGO) as its electrodes. Such GO actuators were fabricated by evaporating the aqueous dispersion of exfoliated GO nanosheets, followed with in situ reduction of the surface of the GO nanosheets by hydrogen iodide (HI). When subjected to a 3 V electrical field, the GO actuator performed electromechanical bending action with a tip displacement of 5 mm and exhibited a blocking force of 10 gf g -1 for 10 s. In addition, the GO actuator showed an almost identical actuating behavior in cyclic measurements. The durable actuation could be attributed to both the unique lamellar structure of the GO film which blocked the diffusion of cationic clusters and the surface rGO electrodes which protected the interlamellar water from evaporation.
Back Cover: An ionic polymer‐metal composite actuator with mesoporous graphene (MG) as enhanced filler is proposed. MG improves the durability of the actuator, more importantly, it provide additional pathway for the diffusion of cationic clusters and thus enhanced the actution speed. Further details can be found in the article by Lei Zu, Yueting Li, Huiqin Lian,* Yanou Hu, Wei Chang, Bingxin Liu, Yang Liu, Xiang Ao, Qiang Li and Xiuguo Cui* on page 1076.
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