A novel, all-organic electroactive device system has been fabricated with a single-wall carbon nanotube (SWCNT) film used as an alternative electrode. This system was fabricated with LaRC-Electro Active Polymer (LaRC-EAP) active layer and the SWCNT films by pressing at 600, 3,000, and 6,000 psi (≈4.1, 20.7, and 41.4 MPa, respectively). Silicone elastomer plates (3-mm thick) were used on the press plate surfaces for better contact adhesion between the SWCNT film and the actuating layer. This polymeric electroactive device layered with the SWCNT-FE (SWCNT-Film Electrode) can serve as an actuator. The density (or modulus) of the SWCNT-FE can be controlled by adjusting the fabrication pressure. It is anticipated that less dense SWCNT-FE can provide less constrain displacement of the polymeric actuating layer by matching the modulus.

A freestanding, flexible SWCNT-FE has been prepared that shows high electrical conductivity and good thermal stability with comparable modulus to the polymeric active layers. The SWCNT film was created by dispersing SWCNTs into N, N-dimethylacetamide (DMAc) under sonication, and then filtered onto the surface of an anodized alumina membrane (pore size: 0.2 mm) to form a SWCNT film on the membrane. The freestanding SWCNT film is easily delaminated by breaking the brittle alumina membrane, which has the conductivity of 280 S/cm. The thickness of the SWCNT film can be controlled from several tens of nanometers to several hundreds of micrometers by adjusting the concentration and quantity of SWCNT solution used. The SWCNT film, thinner than about 300 nm, is transparent.

The temperature and frequency dependence of the dielectric constant for LaRC-EAP layered with SWCNT-FE is almost the same as that of the dielectric properties of the same LaRC-EAP layered with gold electrodes. The dielectric constant remains unchanged up to 220 °C, and then increases, indicating the SWCNT-FE’s good performance as an electrode. The increase of the dielectric constant at 220 °C is due to the glass transition temperature (Tg) of LaRC-EAP. Above Tg, dipoles have a higher mobility and show a higher dielectric constant. Thermally stable dielectric properties suggest that SWCNT-FE is suitable for high-temperature applications at least up to 220 °C. SWCNT usually does not oxidize up to 400 °C. Success in the use of conducting polymer electrodes at this high temperature has rarely been reported.

Electric field-induced strain values for LaRC-EAP layered with metal electrodes versus LaRC-EAP layered with SWCNT-FE show some interesting differences. The strain of LaRC-EAP layered with SWCNT-FE after pressing at 600 psi (≈4.1 MPa) increased more rapidly than that layered with silver electrodes. As the pressure of the fabrication of the LaRC-EAP/SWCNT-FE system increased, the strain decreased because the SWCNT-FE became denser (and stiffer) and could increasingly constrain the displacement of the active layer. At 6,000 psi (≈41.4 MPa), the strain value was close to that of LaRCEAP with the silver electrodes, which indicates that the modulus of the SWCNT-FE prepared at 6,000 psi (≈41.4 MPa) is close to that of silver electrodes at the interface.

This work was done by Joycelyn S. Harrison and Cheol Park of Langley Research Center, and Jin Ho Kang of National Institute of Aerospace. LAR-17455-1