High performance polymer actuators based on multi-walled carbon nanotubes that surpass the performance of those containing single-walled carbon nanotubes: Effects of ionic liquid and composition

The effects of ionic liquid (IL) and composition (ratio of carbon nanotube (CNT):polymer:IL) on the electrochemical and electromechanical properties of actuators containing activated and non-activated multi-walled carbon nanotube (MWCNT)-IL gel electrodes were investigated. The electrochemical and electromechanical properties of actuators containing the activated and non-activated MWCNT-IL gel electrodes were compared to those of a single-walled carbon nanotube (SWCNT)-based actuator. The double-layer capacitance of the activated MWCNT (MWCNT-COOH) electrode and the strain and maximum generated stress for the MWCNT-COOH or MWCNT actuator are dependent on both the IL and composition. For the MWCNT-COOH actuator containing 1-ethyl-3-methylimidazolium tetrafluoroborate (EMI[BF4]) (MWCNT-COOH:poly(vinylidene fluoride-co-hexafluoropropylene):EMI[BF4] = 30:30:35), the strain was 0.78–0.80% for the frequency range of 0.01–0.005 Hz, which was ca. twice that measured for the SWCNT actuator, and the maximum generated stress was ca. 1.8–2.5 times larger than that observed for the SWCNT actuator. Therefore, the common CNT activated MWCNT actuator can generate a maximum stress sufficient for practical purposes without using specialized SWCNT. Furthermore, the actuator containing MWCNT-COOH performed better than those containing SWCNTs or MWCNTs, and gave a more rapid response.