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 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. (C) 2011 Elsevier B.V. All rights reserved.