Preparation And Electro-Deformation Performance Of Ionic Polymer-Metal Composite

As a new smart material, Ionic Polymer-Metal Composite(IPMC) could exhibit a blending motion towards of its electrodes under a low voltage input. And the actuators fabricated with IPMC materials have widely applications in the fields of soft mechanical actuator, stress sensor, artificial muscle, biomedicine and biomimetic material, due to their unique properties including simple actuating mode, high efficiency, low actuat voltage, safe operation and light weight. In this subject, the ionic polymer EVOH-g-SO₃H was synthesized by sulfonation reaction with the reactive hydroxyl group of EVOH (ethylene vinyl alcohol copolymer) and 1, 3-propane sultone, and then EVOH-g-SO₃H was modified with crosslinking agent glutaraldehyde. Crosslinked EVOH-g-SO₃H film was prepared with solution casting, and IPMC was successfully fabricated by chemical reduction process based on crosslinked EVOH-g-SO₃H film.Studies on preparation of EVOH-g-SO₃H and crosslinked EVOH-g-SO₃H film were carried out at first, including the mechanism of the sulfonation and crosslinking reaction, and the preparation process, chemical structure and thermology property. The surface morphology and condenstate structure of crosslinked EVOH-g-SO₃H film was characterizated with Scanning Electron Microscope(SEM) and Atomic Force Microscope(AFM), separatively. The physical properties of crosslinked EVOH-g-SO₃H film were studied in detail, including water uptake, ion-exchange capacity, crystallinity and mechanical properties. Results showed that the crosslinked EVOH-g-SO₃H film was suitable for fabricating IPMC with the molar ratio of hydroxyl group and 1, 3-propane sultone(rs) less than 1:0.6. There were some ionic cluster structure in crosslinked EVOH-g-SO₃H film with the help of atomic force microscope, and the diameter was about 20⁷0nm.The fabrication process and mechanism of IPMC was studied, and the surface and cross-section morphology were characterized with scanning electron microscope. SEM pictures proved a thin layer of Ag metal about 20μm deposited on each membrane surface, and the Ag electrode layer of twice and third chemical reduction were thicker than one. In addition, the densification and planeness of twice and third chemical reduction were better than one.At last, the electro-deformation performance of IPMC was studied with the influence factors of sulfonation degree, water loss rate and applied voltage. The calculation formula of IPMC strain-stress was set up based on a cantilever beam model. The maximum tip displacement of IPMC increased with sulfonation degree increasing. The electro-deformation performance of IPMC could be improved by coating an oil cover in order to reduce water loss. The maximum tip displacement increased as the applied volatge increased or voltage conversion frequency decreased. The electro-deformation repeatability would be excellent when the applied voltage was less than 3V. When the voltage was more than 3V, the increase spread of IPMC electro-deformation reduced, and the maximum tip displacement was smaller and smaller as replication increasing. The electro-deformation reduction increased as the frequency increasesd under a 3V voltage input. Under a 3V square voltage input, when the frequency is 1.0Hz, the electro-deformation was almost disappear after the number of IPMC deformation reached to about 30, and as a 0.5Hz frequency the number of IPMC deformation could reach to about 50. The stress of IPMC deformation reached to 4.56MPa with a 6V voltage applied, based on the strain-stress formula.The studies results indicated there was electro-deformation performance for the IPMC based on non-perfluorinated crosslinked EVOH-g-SO₃H film, and it could be used as a new IPMC material. But there is some problem to resolve, such as how to prepare suitable matrix film, how to improve electro-deformation level and the deformation characterization.