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Ionic liquids (ILs) were synthesized. We herein evaluated the electrochemical and electromechanical properties of actuators based on an ionic fluoropolymer (NafionTM) and a non-ionic fluoropolymer (poly(vinylidene fluoride-co-hexafluoropropylene) [PVdF(HFP)]) gel fabricated using a single-walled carbon nanotube (SWCNT), and containing an IL gel electrode based on aliphatic or cyclic quaternary cations in addition to the perfluoroalkyltrifluoroborate anion. This actuator is an electrochemical window of 6 V. We found that the ionic conductivity of the gel electrolyte layer was dependent on the IL species employed. In addition, the double-layer capacitance of the P14 (N-butyl-N-methylpyrrolidinium) cations was larger than that of the DEME (N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium) cations. Furthermore, the maximum strains of the ±3 V actuators were 1.5–2 times larger than those of the ±2 V actuators, and the maximum generated stresses were 0.35–0.63 MPa in the NafionTM–PVdF(HFP)–SWCNT–IL actuator. These results indicate that PVdF(HFP)/NafionTM-based actuators containing quaternary cations and perfluoroalkyltrifluoroborate anions and with an electrochemical window of 6 V are highly suitable for practical applications

In this study, various ionic liquids (ILs) with electrochemical windows as wide as 6 V were synthesized and their electrochemical and electromechanical properties were evaluated for their application in actuators. These actuators were based on an ionic fluoropolymer (Nafion™)/non-ionic fluoropolymer (poly(vinylidene fluoride‑co‑hexafluoropropylene) [PVdF(HFP)]) gel fabricated using a single-walled carbon nanotube (SWCNT) containing an ionic liquid (IL) gel electrode, which was in turn composed of aliphatic or cyclic quaternary cations and perfluoroalkyltrifluoroborate anions. The ionic conductivity of the gel electrolyte layer was dependent on the IL species employed. In addition, the maximum strains of the ±3-V actuators were 1.5–2-times larger than those of the ±2-V actuators. These results indicated that the Nafion™/PVdF(HFP)-based hybrid actuators, containing quaternary cations and perfluoroalkyltrifluoroborate anions, are ideal for practical applications and could be used as electrochemical materials in wearable and energy conversion devices. After determining the frequency dependences of the displacement responses of the above-mentioned Nafion™/PVdF(HFP)–SWCNT–IL gel hybrid actuators, these results were simulated using a double-layer charging kinetic model. Surprisingly, the simulated curves were similar and comparable to the experimentally obtained ones. The response time constant was determined and was represented by an equivalent circuit comprising a series combination of the ionic resistances and the double-layer capacitance. The Nafion™/PVdF(HFP)–SWCNT–IL (imidazolium-cation-type) gel hybrid actuator was represented by the ionic resistance and double-layer capacitance, in contrast to the PVdF(HFP)–SWCNT–IL (imidazolium-cation-type) actuator, which was represented by the electronic resistance and double-layer capacitance.

The sustainable application of cellulose nanofibers and ionic liquids (ILs) in the fabrication of transparent gel electrolyte actuators combined with thin electrodes remains to be explored. Accordingly, this study developed a new actuator on the basis of a 2,2,6,6-tetramethylpiperidine-1-oxyl radical-oxidized cellulose nanofibers/IL/poly(dimethylsiloxane) (TOCN/IL/PDMS) transparent gel electrolyte. A casting method was employed to prepare the gel electrolyte film, and spray-coating was used to apply thin electrodes. On the basis of its electromechanical and electrochemical properties, the TOCN/IL/PDMS gel electrolyte actuator had high strain performance. The actuator's operational mechanism is based on both electrostatic double-layer capacitor (EDLC) and Faradaic capacitor mechanisms, with the EDLC mechanism having a stronger influence. The actuator's displacement-response frequency dependency was determined, and we simulated the obtained findings by using a double-layer charging kinetic model. The combined gel electrolyte and electrode resistance resulted in a favorable fit to the experimental data, as did the gel electrolyte resistance alone. The performance of the TOCN/IL/PDMS-electrolyte-based polymer actuators can be improved further by designing electrolytes (primarily) and electrodes to have high ionic and electrical conductivities. The films-which are flexible, robust, and transparent-may have potential as actuator materials within electronic and energy-conversion devices that are required to be wearable and transparent.

This study describes new actuators with cellulose nanofibers, single-walled carbon nanotubes and ionic liquids (CNFs/SWCNTs/ILs) and examines the electrochemical and electromechanical properties of CNF/SWCNT/IL gel hybrid actuators. Further, the effects of the CNF species present on the electrode and the electrolyte layer species of poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF(HFP)) or CNF/IL on the electrochemical and electromechanical properties of the low-voltage electroactive polymer actuators are investigated. The CNF/SWCNT/IL structure revealed a network of highly entangled CNFs and SWCNTs. The results indicated that the CNF/SWCNT/IL electrodes and the PVdF(HFP)/IL electrolyte actuators can significantly outperform the CNF/SWCNT/IL electrodes and the CNF/IL electrolyte actuators. PVdF(HFP) was considered to be a better polymer electrolyte than CNF. Further, the frequency dependences of the displacement responses of these CNF/SWCNT/IL electrode actuators were successfully simulated using a double-layered charging kinetic model. The equivalent circuit models exhibited by the PVdF(HFP)/IL electrolyte actuators are different when compared to those exhibited by the CNF/IL electrolyte actuators. Based on the results of this study, the CNF/SWCNT/IL electrodes and the PVdF(HFP)/IL electrolyte actuators are promising for application as electrochemical materials that are useful in real-world applications, including wearable and energy-conversion devices.

This paper presents the development of a new transparent actuator prepared from poly(dimethylsiloxane)/ionic liquid (PDMS/IL) gel electrolyte. The gel electrolyte film is prepared using a casting method and thin electrodes are applied by spray coating. Subsequently, the electrochemical and electromechanical properties of the PDMS/IL gel electrolyte actuator are investigated, which reveal its superior strain performance. The functioning mechanism of the actuator appears to originate from both the electrostatic double-layer capacitor (EDLC) and Faradaic capacitor (FC) mechanisms, with greater contribution of the former. These transparent, flexible, and robust films may have significant potential as actuator materials for wearable and transparent electronic and energy-conversion devices.

The electrochemical and electromechanical properties of poly(vinylidene fluoride-co-hexafluoropropylene)-based actuators using graphene oxide (GO) or graphene (G)/vapor grown carbon fiber (VGCF)/ionic liquid (IL) composite gel electrodes formed are compared with those of actuators using only GO, only G, and only SWCNT. We compare the results with previous results on actuators with electrodes based on single-wall carbon nano-tubes (SWCNTs). In the frequency range 0.005–10 Hz, the GO/VGCF/IL and G/VGCF/IL actuators exhibit higher strains than actuators fabricated without VGCF. For the GO/VGCF/IL actuators, the maximum strain is greater than for actuators made with only GO or only VGCF. The maximum strain for the GO/VGCF/EMI[BF4] actuators is 56% greater than that for an SWCNT-based actuator (GO:VGCF ratio of 7:1)—sufficient for possible practical applications. The maximum generated stress obtained for the GO/VGCF/EMI[TFSI] actuators is 10% greater than that for an SWCNT-based actuator. The maximum generated stresses for GO/VGCF/IL and G/VGCF/IL actuators are greater than those for actuators made with only GO or only G. For a limited number of GO:VGCF and G:VGCF ratios, an electrochemical kinetic model, similar to that used for SWCNT-based actuators, successfully predicts the frequency dependence of the displacement response for GO/VGCF and G/VGCF actuators. These results suggest that flexible, robust films enabled by the synergistic effect obtained by combining graphene and VGCFs can have significant potential as actuator materials for wearable and energy-conversion devices.

In a previous study that the authors have conducted, actuators based on cellulose nanofibre/poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate)/ionic liquid (CNF/PEDOT:PSS/IL) gel electrodes and CNF/IL gel electrolytes could not be fabricated due to poor adhesion between the electrode and electrolyte layers. However, in this study, a series of novel actuators were developed using a 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-oxidised cellulose nanofibre (TOCN)/PEDOT:PSS/IL gel electrode with a TOCN/IL or poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF(HFP)/IL) gel electrolyte due to good adhesion between the electrode and electrolyte layers. The TOCN/PEDOT:PSS/IL gel electrode actuators exhibited high strain performance. These actuators mainly operated via an electrostatic double-layer capacitor mechanism, with a redox capacitor mechanism making a relatively small contribution. The TOCN/PEDOT:PSS/IL gel electrode actuators showed frequency-dependent displacement responses, and a model of double-layer charging kinetics considering the combined resistance of the gel electrode/electrolyte successfully simulated the experimental results. The development of electrodes with excellent electrical conductivity (PVdF(HFP)/IL electrolytes) and electrodes/electrolytes with excellent electrical and ionic conductivities (TOCN/IL gel electrolytes) will facilitate the optimisation of the performance of TOCN/PEDOT:PSS/IL-based polymer actuators. These flexible films will be applicable for the development of actuator materials for use in wearable and transparent electronic and energy conversion devices.

This paper describes new actuators with poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate)/vapor-grown carbon fibre/ionic liquid (PEDOT:PSS/VGCF/IL) structures, as an alternative to those incorporating single-walled carbon nanotubes (SWCNTs). These devices show superior strain performance compared to those using SWCNTs in place of VGCFs or poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF(HFP)) instead of PEDOT:PSS. These improvements are attributed to be obtained from simultaneous electrostatic double-layer (EDLC) and faradaic capacitor (FC) mechanisms. The electrode in the new actuator system represents an electrochemical capacitor composed of an EDLC and an FC, since PEDOT:PSS (used as a substitute for PVdF(HFP)) acts as both an FC and a base polymer. In addition, the VGCF skeleton increases the electroconductivity of the device and provides an EDLC effect. The functioning mechanism of this device therefore differs from those of conventional actuators, which act solely as EDLC units. The PEDOT:PSS polymer helps to increase the specific capacitance, strain, and maximum generated stress values compared to those obtained with a conventional actuator. Surprisingly, the synergistic effect from the combination of the PEDOT:PSS and VGCFs is much greater than the enhancement achieved by combining PEDOT:PSS and SWCNTs. For this reason, these new, flexible and robust films may have significant potential as actuator materials for wearable energy conversion devices. A double-layer charging kinetic model was developed to account for the oxidation and reduction reactions of PEDOT:PSS, and this model is similar to that previously proposed for PEDOT:PSS/SWCNT/IL actuators. The model was successfully applied to simulate the frequency-dependent displacement response of the actuators.

The electrochemical and electromechanical properties of polymer actuators that leverage the synergistic effect from combining a noble metal oxide (iridium oxide dihydrate (IrO 2 ·2H 2 O)), vapor-grown carbon nanofibers (VGCFs) and an ionic liquid (IL) in the electrode were compared with those of actuators prepared using VGCFs or single-walled carbon nanotubes (SWCNTs) without IrO 2 , or with an IrO 2 ·2H 2 O/carbon black (CB)/IL composition. The electrode in this actuator system is equivalent to an electrochemical capacitor, and exhibits behavior similar to that of both an electrostatic double-layer capacitor (EDLC) and a faradaic capacitor (FC). The mechanism underlying the functioning of the IrO 2 ·2H 2 O/VGCF/IL actuators which exhibit from both EDLC and FC mechanisms was found to be different from that for devices produced using VGCFs or SWCNTs alone (which exhibit only the EDLC mechanism) and using IrO 2 ·2H 2 O/CB/IL, which exhibit from both EDLC and FC mechanisms, with the FC mechanism providing the largest contribution. An IrO 2 ·2H 2 O/VGCF/EMI[BF 4 ] actuator exhibited a maximum strain of 0.75%, a value approximately 1.8 times that obtained from a SWCNT-only actuator. This device also generated a maximum blocking force stress of 2.58 MPa (1.3 times that of a SWCNT-only actuator) and a maximum calculated stress of 0.66 MPa (2.2 times that of a IrO 2 ·2H 2 O/CB/EMI[BF 4 ] actuator). Although the frequency dependence of the displacement responses of an IrO 2 ·2H 2 O/CB/IL polymer actuator was not successfully simulated using a double-layer charging kinetic model in previous work, this was found to be possible for the IrO 2 ·2H 2 O/VGCF/IL actuators in the present study. Simulations of the electromechanical response of the IrO 2 ·2H 2 O/VGCF/IL actuators correctly predicted strains at low frequencies as well as the associated time constants, confirming that the model is applicable to both EDLC-based actuator systems and the newly fabricated EDLC/FC system. These results suggest that flexible, robust films enabled by the synergistic effect obtained by combining noble metal oxides and VGCFs can have significant potential as actuator materials for wearable and energy-conversion devices.

The electrochemical and electromechanical properties of actuators based on an ionic fluoropolymer (Nafion™) and non-ionic fluoropolymer (poly(vinylidene fluoride-co-hexafluoropropylene) [PVdF(HFP)]) gel fabricated using a single-walled carbon nanotube (SWCNT) – an ionic liquid (IL) gel electrode, were compared with those of actuators based on a non-ionic fluoropolymer (PVdF(HFP)). The ionic conductivity of the Nafion™–PVdF(HFP)–IL gel electrolyte was lower than that of the PVdF(HFP)–IL gel electrolyte. We assume that an ion complex exists between the Nafion™ SO3− anions and imidazolium cations but not between PVdF(HFP) and the imidazolium cations. This Nafion™–PVdF(HFP)–IL gel hybrid actuator mechanism resembled that of an ionic–polymer–metal composite actuator, where the IL molecules move with the IL cations and anions. The maximum strain and maximum generated stress for the Nafion™–PVdF(HFP)–SWCNT actuator with a PVdF(HFP) : Nafion™ ratio of 1 : 3 and a bis(trifluoromethanesulfonyl)imide-containing IL were approximately 1.6 and 1.5 times higher, respectively, than the corresponding values for the PVdF(HFP)–SWCNT–IL actuator. These results indicate that ionic and non-ionic fluoropolymer-based actuators outperform non-ionic fluoropolymer-based actuators and are highly suitable for practical applications. In addition, the frequency dependence of the displacement response of the ionic and non-ionic fluoropolymer–SWCNT–IL actuator was successfully simulated using an electrochemical kinetic model. The results yielded the strain in the low-frequency limit, which was related to the electromechanical mechanism involved, and the time constant of the response, which was represented by an equivalent circuit with the ionic resistance and double-layer capacitance in series, in contrast to the non-ionic fluoropolymer–SWCNT–IL actuator represented by the electronic and ionic resistance and double-layer capacitance.

New hybrid-type poly(3,4-ethylenedioxythiophene) (PEDOT) actuators produced by the film-casting method, in which both electrostatic double-layer (EDLC) and faradaic capacitors (FCs) occur simultaneously, have been developed. The electrochemical and electromechanical properties ofpoly(4-styrenesulfonate) (PSS), PEDOT:PSS/ionic liquid (IL), andPSS/single-walled carbon nanotubes (SWCNTs)/IL actuators are compared with those of a conventional poly(vinylidene fluoride)-co-hexafluoropropylene (PVdF(HFP))/SWCNT/IL actuator. It is found that thePSS/SWCNT/IL actuator provides a better actuation strain performance than a conventional (PVdF(HFP))/SWCNT/IL actuator, as its electrode is an electrochemical capacitor (EC) composed of an EDLC and FC. ThePSS polymer helps produce a high specific capacitance, actuation strain, and maximum generated stress that surpass the performance of a conventional PVdF(HFP) actuator. The flexible and robust films created by the synergistic combination of PEDOT and SWCNT may therefore have significant potential as actuator materials for wearable energy-conversion devices. A double-layer charging kinetic model was successfully used to simulate the frequency dependence of the displacement responses of thePSS/IL andPSS/SWCNT/IL actuators.

This study proposes novel actuators based on cellulose nanofibre/poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate)/hydrous ruthenium oxide/ionic liquid (CNF/PEDOT:PSS/RuO2/IL) electrodes and the poly(vinylidene fluoride-co-hexafluoropropylene)/IL (PVdF(HFP)/IL) electrolyte, and investigates the effect of hydrous ruthenium oxide on the electrochemical and electromechanical properties of the proposed actuators. The proposed system contains an electrochemical capacitor electrode, which acts as both a faradaic capacitor (FC) and a small electrostatic double layer capacitor (EDLC). This hybrid capacitor is based on the FC (RuO2) mechanism, and a base polymer (PEDOT:PSS) and CNF skeleton replace carbon nanotubes (CNTs). Therefore, this device functions differently from traditional CNT/PVdF(HFP))/IL electrode actuators, which are only used as EDLC units, and CNF/PEDOT:PSS/IL (without RuO2) actuators, where PEDOT:PSS plays the role of both FC and base polymer. Devices built using the proposed actuators exhibit higher strains and greater maximum generated stresses than those exhibited by devices based on CNF/PEDOT:PSS/IL (i.e. without RuO2). Surprisingly, the synergism obtained by combining RuO2 and PEDOT:PSS is considerably greater than the enhancement achieved using PEDOT:PSS. The frequency dependences of the displacement responses of the CNF/PEDOT:PSS/RuO2/IL electrode actuators were then measured and successfully simulated using a double layered charging kinetic model. The developed films are novel, robust, and flexible, and they exhibit potential for use as actuator materials.

This study describes new actuators with cellulose nanofibers, single-walled carbon nanotubes and ionic liquids (CNFs/SWCNTs/ILs) and examines the electrochemical and electromechanical properties of CNF/SWCNT/IL gel hybrid actuators. Further, the effects of the CNF species present on the electrode and the electrolyte layer species of poly(vinylidene fluoride

This paper describes new actuators with cellulose nanofiber/poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate)/ionic liquid (CNF/PEDOT:PSS/IL) structures. Devices containing these structures exhibit higher strain and maximum generated stress than those based on only PEDOT:PSS/IL. The new actuator system contains an electrode, which is an electrochemical capacitor, and which consists of both a faradaic capacitor (FC) and a small electric double-layer capacitor (EDLC), i.e., PEDOT:PSS. This combined capacitor plays the role of an FC and a base polymer, and the CNF skeleton is used in the place of carbon nanotubes (CNTs). This device therefore functions differently from traditional CNT/PVdF–HFP/IL actuators, which are only used as EDLC units and from PEDOT:PSS/vapor-grown carbon nanofibers (VGCF)/IL actuators, which are used as hybrid (FC and EDLC) units. The developed films are novel, robust, and flexible, and demonstrate potential as actuator materials for wearable energy-conversion devices. A double-layer charging kinetic model, which is similar to that previously proposed for PEDOT:PSS/CNT/IL actuators, is developed to explain the oxidation and reduction of PEDOT:PSS. This model successfully simulates the frequency-dependent displacement response of actuators.

This paper describes the effect of ethylene glycol on the performance of actuators with poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate)/vapor-grown carbon fiber/ionic liquid/ethylene glycol (PEDOT:PSS/VGCF/IL/EG) structures. These devices exhibit superior strain performances compared to devices using PEDOT:PSS/VGCF/IL. EG is assumed to assist in the formation of three-dimensional conducting networks between small PEDOT:PSS domains. This is because it helps to remove insulating PSS from the surface of the PEDOT/PSS grains and facilitates the crystallization of PEDOT. Therefore, EG helps to increase the specific capacitance, strain, and maximum generated stress compared to the values obtained using a PEDOT:PSS/VGCF/IL actuator. Therefore, these new, flexible, and robust films may have significant potential for their use as actuator materials in wearable energy conversion devices. A double-layer charging kinetic model was developed to account for the oxidation and reduction reactions of PEDOT:PSS, and this model is similar to that proposed for PEDOT:PSS/VGCF/IL/EG actuators. This model was successfully applied to simulate the frequency-dependent displacement responses of the actuators.

The electrochemical and electromechanical properties of actuators fabricated from activated and non-activated multi-walled carbon nanotube (MWCNT)-ionic liquid (IL) gel electrodes are compared with single-walled carbon nanotube (SWCNT)-based actuators. The double-layer capacitance of the MWCNT-COOH electrode was larger than that of the MWCNT electrode but smaller than that of the SWCNT electrode. The activated MWCNT-COOH polymer actuator surpassed the SWCNT actuator in terms of the strain and maximum generated stress.

The electrochemical and electromechanical properties of poly(vinylidene fluoride-co-hexafluoropropylene) actuators were investigated using a non-activated multi-walled carbon nanotube (MWCNT)–ionic liquid (IL) gel electrode containing manganese oxide (MnO2) on various ILs. The MnO2/MWCNT/IL actuators surpassed the strain and maximum generated stress performance observed for the only-MWCNT and only-SWCNT actuators on all ILs. These actuators are different from only-MWCNT and only-SWCNT actuators, which act solely as electrostatic double-layer capacitor (EDLC) units. The frequency dependence of the displacement responses of the MnO2·xH2O/MWCNT/IL polymer actuators was successfully simulated using a double-layer charging kinetic model. Two parameters for the simulation were determined: the strain at the low frequency limit and the time constant. Simulations of the electromechanical response of the MnO2·xH2O/MWCNT/IL actuators predicted strains at low frequencies as well as at the associated time constant, confirming that the model is applicable not only to EDLC-based actuator systems but also to the fabricated EDLC/FC system. These results suggest that flexible, robust films, fabricated from metal oxides and MWCNTs that function synergistically, are potential candidates for actuator materials that can be applied in wearable and energy conversion devices.

The electrochemical and electromechanical properties of polymeric actuators prepared using iridium oxide (IrO 2 ) or ruthenium oxide (RuO 2 )/carbon black (CB)/ionic liquid (IL) electrodes and formed without ultrasonication were compared with actuators prepared using solely CB or single-walled carbon nanotubes (SWCNTs) with an IL. The IrO 2 /CB/IL actuators surpassed the strain performance of the CB and SWCNT-only actuators. The electrode in these actuator systems appears to represent an electrochemical capacitor (EC) composed of an electrostatic double-layer (EDLC) and a faradaic capacitor (FC), the latter of which primarily determines the capacitance. The CB functions largely by increasing the electroconductivity of the actuator. The functioning mechanisms of these actuators are different from those of CB and SWCNT-only actuators, which act solely as EDLC units. Both metal oxide (MO 2 ) and CB are required to produce high strain values that surpass the performance of SWCNT polymer actuators and are suitable for practical applications. The actuator displacement response frequency dependence could not be simulated using an electrochemical kinetic model derived for CB/VGCF/IL and SWCNT-based actuators. This model appears to apply only to EDLC-based actuator systems and thus does not pertain to the present EDLC/FC system, in which the capacitance of the electrode comes primarily from the FC effect.

The electrochemical and electromechanical properties of polymeric actuators prepared using nickel peroxide hydrate (NiO2·xH2O) or nickel peroxide anhydride (NiO2)/vapor-grown carbon nanofibers (VGCF)/ionic liquid (IL) electrodes were compared with actuators prepared using solely VGCFs or single-walled carbon nanotubes (SWCNTs) and an IL. The electrode in these actuator systems is equivalent to an electrochemical capacitor (EC) exhibiting both electrostatic double-layer capacitor (EDLC)- and faradaic capacitor (FC)-like behaviors. The capacitance of the metal oxide (NiO2·xH2O or NiO2)/VGCF/IL electrode is primarily attributable to the EDLC mechanism such that, at low frequencies, the strains exhibited by the NiO2·xH2O/VGCF/IL and NiO2/VGCF/IL actuators primarily result from the FC mechanism. The VGCFs in the NiO2·xH2O/VGCF/IL and NiO2/VGCF/IL actuators strengthen the EDLC mechanism and increase the electroconductivity of the devices. The mechanism underlying the functioning of the NiO2·xH2O/VGCF/IL actuator in which NiO2·xH2O/VGCF = 1.0 was found to be different from that of the devices produced using solely VGCFs or SWCNTs, which exhibited only the EDLC mechanism. In addition, it was found that both NiO2 and VGCFs are essential with regard to producing actuators that are capable of exhibiting strain levels greater than those of SWCNT-based polymer actuators and are thus suitable for practical applications. Furthermore, the frequency dependence of the displacement responses of the NiO2·xH2O/VGCF and NiO2/VGCF polymer actuators were successfully simulated using a double-layer charging kinetic model. This model, which accounted for the oxidization and reduction reactions of the metal oxide, can also be applied to SWCNT-based actuators. The results of electromechanical response simulations for the NiO2·xH2O/VGCF and NiO2/VGCF actuators predicted the strains at low frequencies as well as the time constants of the devices, confirming that the model is applicable not only to EDLC-based actuator systems but also to the fabricated EDLC/FC system.

The electrochemical and electromechanical properties of actuators based on the polymer electrolyte poly(ethylene oxide) (PEO), fabricated using a single-walled carbon nanotube (SWCNT)-ionic liquid (IL)-based gel electrode, were compared with those of actuators based on poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF(HFP)). The ionic conductivity of the PEO/IL gel electrolyte layer was much smaller than that of the PVdF(HFP)/IL layer. This is likely because the interaction between the oxygen atoms of PEO and the cations of the IL was larger than that between the fluorine atom of PVdF(HFP) and the IL cations. The maximum strain of the PEO electrolyte layer was smaller than that of the PVdF(HFP) electrolyte layer. Further, the maximum strain of an EMI[TFSI]/PEO electrode-based actuator was approximately 1.3 times larger than that of an EMI[TFSI]/PVdF(HFP) electrode-based actuator, where EMI[TFSI] is 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide. These results indicated that the PEO electrode-based actuators exhibited better performances than those based on a PVdF(HFP) electrode. In the case of the PEO electrode-based actuators, it was also found that the ion size, and the self-diffusion coefficient, as well as the rate of ion transport in the electrodes and electrolyte, were of critical importance for realizing low-voltage actuators. Finally, a simple model for the actuation mechanism was also proposed. The model, which was based on the product of the ionic transport number and the ionic volume, was shown to successfully explain the actuator behavior.

The electrochemical and electromechanical properties of poly(vinylidene fluoride- co -hexafluoropropylene) based actuators using carbon black (CB)/vapor grown carbon fiber (VGCF)/ionic liquid (IL) composite gel electrodes formed without ultrasonication were compared with those of actuators using only CB or VGCF. The double-layer capacitance of the CB/VGCF/IL electrodes was larger than that of the CB/IL electrodes and increased with VGCF content. The amount of strain exhibited by the CB/VGCF/IL actuators was also larger than that for the CB/IL actuators, with the highest strain being produced for an actuator with a CB:VGCF ratio of 1:1. This was slightly larger than that for a polymer actuator using single-walled carbon nanotubes (SWCNTs), indicating that the proposed actuators exhibit sufficiently high performance for real-world applications without the need for expensive SWCNTs. Furthermore, the frequency dependence of the displacement response of the CB/VGCF/IL polymer actuators was successfully simulated using an electrochemical kinetic model similar to that for SWCNT-based actuators. The results yielded the strain in the low-frequency limit and the time constant of the response.

This study focused on poly(vinylidene fluoride-co-hexafluoropropylene) based actuators containing single-walled carbon nanotubes. The actuators used composite gel electrodes and electrolytes that included an ionic liquid (IL) having an electrochemical window of 6 V. A comparison was made of the electrochemical and electromechanical properties of actuators with ILs composed of different quaternary ammonium or phosphonium cation species. Either bis(trifluoromethanesulfonyl)imide (TFSI) or tetrafluoroborate (BF4) was used as the anion species. For TFSI based electrode layers, the double-layer capacitance was found to depend on the type of IL cations present. At an applied voltage of ±2 V, the strain showed a dependence on the self-diffusion coefficient in both the kinetic and static regions of the strain–frequency curve. This was also the case for the kinetic region at an applied voltage of ±3 V. The maximum strain and stress were produced by an actuator with an IL composed of N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium bis(trifluoromethanesulfonyl)imide and were approximately 2 times larger than those for an actuator with an IL composed of 1-ethlyl-3-methylimidazolium tetrafluoroborate, with an electrochemical window of just 4 V. This indicates that actuators with an electrochemical window of about 6 V are promising candidates for real-world applications. It was found that the ion size, self-diffusion coefficient and ion transport in the electrodes and electrolyte are important for realizing low-voltage electroactive polymer actuators. A simple model for the actuation mechanism was proposed, based on the product of the ionic transport number and the ionic volume, and it was shown to successfully explain the actuator behavior.

The effects of Li tetrafluoroborate (Li[BF4]) and lithium bis(trifluoromethanesulfonyl)imide (Li[TFSI]) salts on the electrochemical and electromechanical properties of an actuator using a poly(vinylidene fluoride-co-hexafluoropropylene)-supported vapor grown carbon fiber (VGCF)/ionic liquid (IL) gel electrode formed without ultrasonication were investigated. At a slow sweep rate of 1 mV s−1, the measured double-layer capacitance values for the VGCF/Li[X]/IL actuator were in the range of 20.0–42.3 F g−1, and were larger than that for an IL-only actuator. The capacitance was found to increase with the Li[BF4] content, but was independent of the Li[TFSI] content. All of the VGCF/Li[X]/IL actuators exhibited a larger amount of strain than IL-only actuators, and for a VGCF/Li[TFSI]/EMI[TFSI] actuator with a Li[TFSI]/EMI[TFSI] molar ratio of 1.0, the maximum strain was greater than that for an IL actuator containing single-walled carbon nanotubes. Moreover, the frequency dependence of the displacement response for the VGCF/Li[X]/IL actuators was successfully simulated using an electrochemical kinetic model, similar to the case for SWCNT and VGCF based actuators containing metal oxide. The results yielded the strain in the low-frequency limit in addition to the time constant of the response.

The effects of metal oxide and an ionic liquid (IL) on the electrochemical and electromechanical properties of poly(vinylidene fluoride-co-hexafluoropropylene) actuators were investigated using a vapor grown carbon nanofiber (VGCF)-IL gel electrode containing metal oxide, formed without using ultrasonication. The double-layer capacitance of the VGCF electrode containing MnO2 was larger than that of electrodes containing either only VGCF or RuO2/VGCF. A MnO2/VGCF electrode containing 1-ethyl-3-methylimidazolium tetrafluoroborate (EMI[BF4]) gave the largest capacitance of those tested. The VGCF polymer actuator containing MnO2 surpassed the performance, in terms of strain and maximum generated stress, of actuators prepared with VGCF only, RuO2/VGCF, or single-wall carbon nanotubes (SWCNTs) only. The MnO2/VGCF actuator containing EMI bis(trifluoromethanesulfonyl)imide (EMI[TFSI]) gave the largest strain and the MnO2/VGCF actuator containing EMI[BF4] gave the largest maximum generated stress. The capacitance of the MnO2/VGCF/IL electrode and the strain for the MnO2/VGCF/IL actuator contribute to the pseudocapacitance. Both VGCF and MnO2 are necessary to produce actuators with large and rapid responses that surpass the performance of polymer actuators containing only VGCF, RuO2/VGCF, and only SWCNTs. Furthermore, the frequency dependence of the displacement response of the RuO2 or MnO2/VGCF polymer actuator was successfully simulated using an electrochemical kinetic model. The result for simulation of the electromechanical response of the RuO2 or MnO2/VGCF actuators provided the strain at a limit of low frequency and the time constant for the simulation.

The electrochemical and electromechanical properties of actuators prepared using a carbon black (CB)-ionic liquid (IL) gel electrode containing manganese oxide (MnO2) and formed without ultrasonication were compared with actuators prepared using only-CB, only-multi-walled carbon nanotubes (MWCNTs), only-activated multi-walled carbon nanotubes (MWCNT-COOH) and only-single-walled carbon nanotubes (SWCNTs). The CB polymer actuator containing MnO2, prepared without ultrasonication, surpassed the strain performance of the only-CB, only-MWCNT, only-MWCNT-COOH and only-SWCNT actuators. The capacitance of the MnO2/CB/IL electrode contributes to the pseudocapacitance, and for low frequencies, the strain for the MnO2/CB/IL actuator is the dominant contributor to the pseudocapacitance. Therefore, it is considered that the mechanism for MnO2/CB/IL actuation is different from that for the only-SWCNT and only-MWCNT-COOH actuators. Both CB and MnO2 are required to produce a large strain actuator that surpasses the performance of the SWCNT polymer actuator and has characteristics sufficient for practical applications (e.g., in tactile displays).

Actuators were developed using activated multi-walled carbon nanotube (MWCNT)–ionic liquid (IL) gel electrodes, and were compared with non-activated MWCNT- and single-walled carbon nanotube (SWCNT)-based actuators, in terms of their electrochemical and electromechanical properties. Furthermore, the effects of variations in the IL on the electrochemical and electromechanical properties of the activated MWCNT–NH2/IL gel electrode actuators were investigated. The performance of the activated MWCNT–NH2 polymer actuator surpassed that of the SWCNT actuator, in terms of the strain and maximum generated stress. For the MWCNT–NH2 actuators, the strain and maximum generated stress were dependent on the IL species.

The electrochemical and electromechanical properties of poly(vinylidene fluoride- co -hexafluoropropylene) actuators developed using multi-walled carbon nanotube (MWCNT)-ionic liquid gel electrode containing manganese oxide (MnO 2 ) were compared with those using ionic gels with only-MWCNTs, with MWCNTs and ruthenium oxide (RuO 2 ) or with only-single-walled carbon nanotube (SWCNTs). The double-layer capacitance of the MWCNT electrode containing MnO 2 was larger than the one with the MWCNT electrode containing RuO 2 , only-MWCNTs or only-SWCNTs. Furthermore, the MWCNT electrode containing MnO 2 exceeded the performance of the other three actuators in terms of both strain and maximum generated stress. Both MWCNTs and MnO 2 were required to produce large strain and quick response actuators that surpassed the performance of the polymer actuator containing only-SWCNTs.

The electrochemical and electromechanical properties of actuators developed using a non-activated multi-walled carbon nanotube (MWCNT)–ionic liquid (IL) gel electrode containing ruthenium oxide (RuO2) were compared with only-MWCNT and only-single-walled carbon nanotube (SWCNT) based actuators. The double-layer capacitance of the non-activated MWCNT electrode containing RuO2 was larger than that of the only-MWCNT electrode. The non-activated MWCNT polymer actuator containing RuO2 surpassed the performance of the only-MWCNT and only-SWCNT actuators in terms of the strain and maximum generated stress. Both MWCNTs and RuO2 were required to produce large strain and quick response actuators that surpassed the performance of the only-SWCNT polymer actuator and exhibited characteristics sufficient for practical applications (e.g. tactile display).

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[BF 4 ]) (MWCNT-COOH:poly(vinylidene fluoride- co -hexafluoropropylene):EMI[BF 4 ] = 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.

Actuators were developed using activated and non-activated multi-walled carbon nanotube (MWCNT)–ionic liquid (IL) gel electrodes and compared to a single-walled carbon nanotube (SWCNT)-based actuator with respect to the electrochemical and electromechanical properties. The activated MWCNT–COOH/polymer actuator surpassed the SWCNT/polymer actuator in terms of the generated strain.

The effects of polymer species (poly(vinylidene fluoride)) (PVdF) homopolymer or poly(vinylidene fluoride- co -hexafluoropropylene) (PVdF(HFP) copolymer), average molecular weight of the polymer, and the HFP content in PVdF(HFP) on the electrochemical and electromechanical properties of actuators using polymer-supported single-walled carbon nanotube (SWCNT)–ionic liquid (IL) gel electrodes were investigated. For the PVdF (Kynar 741 or 761) actuator containing 1-ethyl-3-methylimidazolium tetrafluoroborate (EMI[BF 4 ]), the generated strain was 0.90–1.05% for the frequency range of 0.01–0.005 Hz, which was over twice as large as that for the PVdF(HFP) (Kynar Flex 2801) actuator. Furthermore, it is considered that the HFP content should be low (or zero) for large generated strain and zero for large maximum stress. The PVdF actuator performs much better than the PVdF(HFP) actuator and has a quick response, sufficient for practical application (e.g., tactile displays).

In this study, we investigated a dependence of anionic species of ionic liquids (ILs) (IL: perfluoroalkyltrifluoroborate anions ([C n F 2 n +1 BF 3 ] − ( n = 0, 1, 2) and bis(perfluoroalkylsulfonyl)imide anions ([(C m F 2 m +1 SO 2 )(C n F 2 n +1 SO 2 )N] − ( m , n = 0, 1, 2)) on electrochemical and electromechanical properties. 1-Ethyl-3-methylimidazolium (EMI + ) was selected as a cation for ILs. 1-Ethyl-3-methylimidazolium trifluoromethyltrifluoroborate (EMI[CF 3 BF 3 ]), 1-ethyl-3-methylimidazolium pentafluoroethyltrifluoroborate (EMI[CF 3 CF 2 BF 3 ]), 1-ethyl-3-methylimidazolium fluorosulfonyl(trifluoromethylsulfonyl)imide (EMI[FTA]) and 1-ethyl-3-methylimidazolium pentafluoroethylsulfonyl(trifluoromethylsulfonyl)imide (EMI[C 1 C 2 ]) were synthesized according to the literatures. The generated strains of the bucky-gel electrodes of the actuators containing EMI[CF 3 BF 3 ] (in the high frequency range: 10–0.5 Hz) and EMI[CF 3 CF 2 BF 3 ] (in the high frequency range of 1–0.5 Hz) are larger than that containing EMI[BF 4 ] (that is to say the quick response). For low frequencies (0.1–0.005 Hz), the generated strain containing EMI[CF 3 CF 2 BF 3 ] was larger than those containing other ILs (EMI[C n F 2 n +1 BF 3 ] ( n = 0, 1) and EMI[(C m F 2 m +1 SO 2 )(C n F 2 n +1 SO 2 )N] ( m , n = 0, 1, 2)). The Young's modulus of actuators containing EMI[CF 3 BF 3 ] and EMI[CF 3 CF 2 BF 3 ] were 145 and 110 MPa, respectively. The melting points of EMI[CF 3 BF 3 ] and EMI[CF 3 CF 2 BF 3 ] are lower than that of EMI[BF 4 ]. Therefore, trifluoromethyltrifluoroborate ([CF 3 BF 3 ] − ) and pentafluoroethyltrifluoroborate ([CF 3 CF 2 BF 3 ] − ) anions performed much better as the actuator using the polymer-supported bucky-gel electrode containing the IL. These results are considered to be the actuator enough to apply actual applications (e.g. tactile display).

The rate property of Li/LiCoO2 cell using ionic liquids (ILs) containing fluorosulfonyl(trifluoromethylsulfonyl) amide (FTA−) anion and N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium (DEME+) was investigated. comparing with corresponding amide ionic liquids composed of such bis(trifluoromethyl)sulfonylamide (TFSA−) and bis(fluoromethylsulfonyl)amide (FSA−). As a result, the cell using DEME[FTA] was also exhibit good rate performance as in the case of DEME[FSA]. This result suggests that an existence of FSO2 group in anionic species might be a key factor to improve the battery performance containing neat ILs.

We investigated an effect for alkaline metal salts or an alkaline earth metal salt on electrochemical and electromechanical properties of an actuator using a single-walled carbon nanotube (SWCNT)-ionic liquid (IL) gel electrode, and much better performance of the actuator containing the metal salt/IL. The actuator containing the alkaline metal salt /IL or alkaline earth metal salt/IL performed much better than that containing only the IL. It is considered that the higher ionic conductivity of the gel electrolyte layer containing the alkaline metal salt /IL or alkaline earth metal salt/IL produces the quick response actuator, and that the large capacitance gives the large generated strain.

The effects of alkaline earth metal salts (Magnesium bis(trifluoromethanesulfonyl)imide (Mg[TFSI] 2 ) and Calcium bis(trifluoromethanesulfonyl)imide (Ca[TFSI] 2 )) on electrochemical and electromechanical properties of an actuator using a polymer-supported single-walled carbon nanotube (SWCNT)-ionic liquid (IL) gel electrode were investigated. The ionic conductivities of the gel electrolyte layers with the molar ratios of Mg[TFSI] 2 /1-ethlyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (EMI[TFSI]) = 0.05, 0.1 and 0.25, and Ca[TFSI] 2 /EMI[TFSI] = 0.05, 0.1 and 0.25 were higher than that containing only EMI[TFSI]. We found large capacitance value 51–89 Fg −1 at a slow sweep rate 1 mV s −1 . The generated strains of the polymer-supported SWCNT-IL gel electrodes of the actuators with the molar ratios of Mg[TFSI] 2 /EMI[TFSI] = 0.1 (in all frequency range; 100–0.005 Hz) and Ca[TFSI] 2 /EMI[TFSI] = 0.05 and 0.1 (in the frequency range; 1–0.005 Hz) were larger than that containing only EMI[TFSI]. In previous paper, the effects of Li salts (Li[BF 4 ] and Li[TFSI]) on the electrochemical and electromechanical properties of an actuator using a polymer-supported SWCNT-IL gel electrode were investigated. Consequently, the generated strain of the actuator with the molar ratios of Mg[TFSI] 2 /EMI[TFSI] = 0.1 is larger than those containing Ca[TFSI] 2 /EMI[TFSI], Li[TFSI]/EMI[TFSI] and Li[BF 4 ]/EMI[BF 4 ] for the wide frequencies (100–0.005 Hz). As the summary, the actuator containing Mg[TFSI] 2 /EMI[TFSI] or Ca[TFSI] 2 /EMI[TFSI] performed much better than that containing only IL. It is considered that the higher ionic conductivity of the gel electrolyte layers containing Mg[TFSI] 2 /EMI[TFSI] or Ca[TFSI] 2 /EMI[TFSI] produces the quick response actuators, and that the large capacitance gives large generated strain. The actuator containing Mg[TFSI] 2 /EMI[TFSI] performed much better than those containing Ca[TFSI] 2 /EMI[TFSI], Li[TFSI]/EMI[TFSI] and Li[BF 4 ]/EMI[BF 4 ] for the wide frequencies (100–0.005 Hz). These results are considered to be the actuator enough to apply actual applications (e.g. tactile display).

The effects of Li salts (Lithium tetrafluoroborate (Li[BF 4 ]) and Lithium bis(trifluoromethanesulfonyl)imide (Li[TFSI])) on the electrochemical and electromechanical properties of an actuator using a polymer-supported single-walled carbon nanotube (SWCNT)-ionic liquid (IL) gel electrode were investigated. The ionic conductivities of the gel electrolyte layers with molar ratios of Li[BF 4 ]/1-ethlyl-3-methylimidazolium tetrafluoroborate (EMI[BF 4 ]) = 0.1 and 0.5, and Li[TFSI]/1-ethlyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (EMI[TFSI]) = 0.1 and 0.3 were higher than those containing only EMI[BF 4 ] and only EMI[TFSI], respectively. We found a large capacitance value 65–96 F/g at a slow sweep rate 1 mV s −1 . The actuator containing Li salt/IL performed much better than that containing only IL. It is considered that the higher ionic conductivity of the gel electrolyte layer containing Li salt/IL produces the quick response actuator, and that the large capacitance gives a large generated strain.

The purpose of this paper is to study an electrochemical property and actuation mechanism of an actuator using same electrolyte and three different electrode (carbon nanotube (SWNT)/ionic liquid (IL)/polymer gel electrode, SWNT/IL gel electrode and Au paste as an electrode) in air, and to investigate the actuator which performs much better. We developed a PVdF(HFP)-IL gel actuator using only Au paste as an electrode layer in air (non-Faradaically driven type), i.e. , the electrode layer was not composed of polymer, IL and SWNT, and the electrolyte layer was composed of polymer and IL. Furthermore, in the previous paper, the electrode layers that laminate the electrolyte layer expanded or contracted, giving rise to a bending motion of the actuator strip (Fig. 1(c) type), in this paper, we showed that, at our conventional actuator (Fig. 1(c) type) and actuator with non-polymer-supported bucky gel electrodes containing internal IL (Fig. 1(b) type), the electrolyte layer also expand or contract, giving rise to a bending motion of the actuator. As a result, we show that polymer-IL gel of the electrolyte is important factor in the field of the low-voltage electroactive polymer (EAP) actuator, and we are considered that these results become the important design principle of the low-voltage EAP actuator.

In this study, we investigated the dependence of anionic species of ionic liquid (IL) on electrochemical properties and actuation mechanism of the actuator using the carbon nanotube-ILs gel electrode. 1-Ethyl-3-methylimidazolium (EMI+) was selected as a cation for ILs. As a result, DCA ([N(CN)2]−) anion performed much better as an actuator using polymer-supported bucky-gel electrode containing internal IL. In low frequencies, the generated strain of polymer-supported bucky-gel electrode of the actuator depended on the size of anion of IL. It, which was the small van der Waals volumes of IL anions (BF4− and [N(CN)2]−), was considered to be large for the usual bending mechanism and the charge injection, in addition, for other bending mechanism of the intercalation/deintercalation into the diameter of the single-walled carbon nanotube (SWNT) and into the SWNT bundles. In addition to that, we compared the actuator using polymer-supported bucky-gel electrode to the actuator using non-polymer-supported bucky-gel electrode. As a result, the generated strain of polymer-supported bucky-gel electrode of the actuator was considered to be attributed to the volume-change for polymer-IL gel of the cathode and that of the anode.

A bucky-gel actuator based on active electrodes composed of activated carbon nanofibers (ACNFs), ionic liquids (ILs) and poly (vinylidene fluoride-co-hexafluoropropylene (PVdF(HFP)) as polymer support have been developed (ACNF-actuator). The frequency dependence of the displacement was measured for the actuators containing seven kinds of ILs. The frequency responses of the ACNF-actuators were one order of magnitude lower than those of the SWCNT-actuators. The reason for this is attributed to the lower conductivity of the ACNF-electrode. In order to improve the response of the ACNF-actuator, the electrode of the actuator was optimized by mixing the ACNFs with SWCNTs (ACNF–SWCNT electrode) or vapor grown carbon fibers (VGCFs) (ACNF–VGCF electrode) for the purpose of increasing the conductivity of the electrode. We have improved the performance of the actuator by optimizing the ratio of the two carbons. We are thus able to tune nano-carbon materials for specific applications of the electromechanical actuator.

In the previous papers, we have reported the first dry actuator that can be fabricated simply by layer-by-layer casting, using ‘bucky gel’, a gelatinous room-temperature ionic liquid (IL) containing single-walled carbon nanotubes (SWNTs). In this paper, the electromechanical and electrochemical properties of the bucky-gel actuators composed of the bucky-gel electrode and the gel electrolyte layers containing seven kinds of internal ILs were studied for exploring the details of the actuation mechanism. We measured the frequency dependence of the displacement response of the bucky-gel actuator and it can be successfully simulated by the electrochemical kinetic model. From the simulated result for the frequency dependence of the electromechanical response of the bucky-gel actuators, we determined two parameters for the simulation, the generated strain at a limit of low frequency and the time constant. The time constant was represented by the equivalent circuit composed of series combination of the ionic resistance R, the double-layer capacitance C and the electrode resistance Rel. The IL-dependence of the time constant was determined by that of the ionic resistance R of the gel electrolyte layer. The generated strain at a limit of low frequency is considered to be related to the electromechanical mechanism of the bucky-gel actuator. From their dependence on the IL species and the theoretical modeling reported in the previous papers, we conclude that both the steric repulsion effect due to the transfer of ions to the electrode and ‘the charge injection’ give the bending motion of the bucky-gel actuator. The volume-changes of the cathode and anode change according to the sizes of the cation and anion, respectively. The ion size gives the dependence of the bending motion of the bucky-gel actuator on the internal ionic species.

The alignment behaviour of triphenylene‐based compounds possessing fluoroalkylated and alkyl side chains was investigated for the hexagonal columnar (Colh) mesophase on polyimide‐, cetyltrimethylammonium bromide (CTAB)‐, and indium tin oxide‐coated glass substrates by polarizing optical microscopy. It was found that 2,6,10‐trinonyloxy‐3,7,11‐tris(1H,1H,2H,2H,3H,3H‐perfluorononyloxy)triphenylene and 2,6,11‐trinonyloxy‐3,7,10‐tris(1H,1H,2H,2H,3H,3H‐perfluorononyloxy)triphenylene exhibit spontaneous homeotropic alignment on these substrates. On the other hand, it was found that 2,6,10‐triheptyloxy‐3,7,11‐tris(1H,1H,2H,2H,3H,3H‐perfluoroheptyloxy)triphenylene, 2,6,11‐triheptyloxy‐3,7,10‐tris(1H,1H,2H,2H,3H,3H‐perfluoroheptyloxy)triphenylene, 2,6,10‐trihexyloxy‐3,7,11‐tris(1H,1H,2H,2H,3H,3H‐perfluorohexyloxy)triphenylene, 2,6,11‐trihexyloxy‐3,7,10‐tris(1H,1H,2H,2H,3H,3H‐perfluorohexyloxy)triphenylene, 2,6,10‐tributyloxy‐3,7,11‐tris(1H,1H,2H,2H,3H,3H‐perfluorobutyloxy)triphenylene and 2,6,11‐tributyloxy‐3,7,10‐...

Two types of homologues (symmetrical and asymmetrical in rotational symmetry) of novel triphenylene compounds possessing fluoroalkyl and alkyl side chains were synthesized via an alternative method. X‐ray diffraction and DSC measurements showed that these homologues are thermotropic liquid crystals with a hexagonal columnar (Colh) mesophase. The phase transition temperatures (Colh–Iso) for both symmetrical and asymmetrical fluoroalkyloxytriphenylenes increase to about 180°C, and are independent of fluoromethylene chain and the rotational symmetry of chemical structure. The Colh phase of symmetrical and asymmetrical fluoroalkyloxytriphenylenes possessing three fluoroalkyl side chains are more stable than fluoroalkyloxytriphenylenes possessing six fluoroalkyl side chains and alkyloxytriphenylenes. The X‐ray diffraction patterns for symmetrical and asymmetrical fluoroalkyloxytriphenylenes, fluoroalkyloxytriphenylenes and alkyloxytriphenylenes in the wide‐angle region are compared.

The alignment behavior of the triphenylene compounds possessing fluoroalkylated side chains was investigated for the hexagonal columnar (Col h ) mesophase on the polyimide-, cetyltrimethylammonium bromide (CTAB)-, and indium-SnO 2 (ITO)-coated glass substrates by polarizing optical microscopy. It was found that 2,3,6,7,10,11-hexakis(1 H ,1 H ,2 H ,2 H ,3 H ,3 H -perfluoroheptyloxy)- and 2,3,6,7,10,11-hexakis(1 H ,1 H ,2 H ,2 H ,3 H ,3 H -perfluorononyloxy)-triphenylenes exhibit a spontaneous homeotropic alignment on these substrates, in contrast to the non-uniformity of alignment of Col h phase in the corresponding hydrocarbon mesogens. On the other hand, it was also found that 4,4,4-trifluorobutyloxy, 4,4,5,5,5-pentafluoropentyloxy and 4,4,5,5,6,6,6-heptafluorohexyloxy derivatives do not show such a spontaneous homeotropic alignment on these substrates. These results indicate that the spontaneous homeotropic alignment of the Col h phase could be easily attained by the introduction of an appropriate number and length of the fluoromethylene chains in the peripheral parts of discogens.

This report discusses the effect of fluoroalkyl chain on the mesomorphism. Several homologues of novel triphenylene compounds possessing fluoroalkylated side chains were synthesized. Studies of X-ray diffraction, DSC and texture observations by polarized microscope revealed that these homologues show hexagonal columnar (Col h ) mesophase. These homologues made columnar mesophase stabilize and the melting point increase, as compared with corresponding alkyloxytriphenylenes. In the case of fluoroalkyloxytriphenylenes possessing fluoromethylene side chains, the increase of the fluoromethylene chain length stabilized columnar mesophase, made the phase transition enthalpy (Col h -Iso) and entropy (Col h -Iso) increase. It is considered that these results are due to the fluorophilic interaction, and that the fluorophilic interaction is important for stabilizing columnar mesophase.

Alignment behavior of a discotic liquid crystalline triphenylene (C8OBTP) on substrates coated with self-assembled monolayers (SAMs) of alkanethiol and asymmetrical alkyl disulfide was investigated by polarized microscopy. Discotic nematic (ND) and rectangular columnar (Colr) phases of C8OBTP shows a different alignment behavior depending on the element of SAMs. C8OBTP exhibits a fan-shaped texture on an alkanethiol SAM in Colr phase, while it has a tendency to show a planar alignment on asymmetrical alkyl disulfide SAM. The different elements of the SAM could influence the alignment behavior of discotic liquid crystal distinctly even in columnar mesophase which has highly self-cohesive forces of systems.

Temperature dependence of infrared spectra for three homologues of the triphenylene mesogens with two terminal carboxylic acids was measured. These mesogens show Colh mesophase. These results revealed the existence of some hydrogen bonding interactions in the isotropic, mesomorphic as well as solid phases. The increase of the dimeric C = O (ca. 1712 cm−1) and the decrease of the monomeric C = O (ca. 1740 cm−1) were observed at the isotropic to Colh phase transition on cooling. The absorption intensity of the dimeric C = O stretching band in Colh phase is larger than that in the isotoropic phase. It was indicated that for the explanation of Colh thermal stability for these homologues molecular rotational fluctuation around the columnar axis in Colh is significantly suppressed by the hydrogen bonding interaction and the suppression depends on the spacer length in their homologues, considering that the thermal stability of Colh phase is related to both the rotational fluctuation and the instability of hexago...

The infrared photoinduced alignment change of liquid-crystal domains was investigated for a hexagonal columnar mesophase of a liquid-crystalline triphenylene derivative. A uniform and anisotropic alignment change of domains was observed when a polarized infrared (IR) light corresponding to the wavelength of the aromatic C–C stretching absorption band of the triphenylene core was used to irradiate the sample. The relationship between the aligned azimuthal angle of the columnar axis and the polarization of the IR incident irradiation was investigated. IR absorption dichroism is induced as a result of the reorientation of triphenylene core. Texture observation and polarizing microscope FTIR spectra show that a change of the molecular alignment occurred and that the direction of columns depends on the polarization angle of the IR light used for irradiation. The mechanism of the alignment change in a columnar liquid crystal film by IR irradiation is also discussed. The technique could provide a novel technology to control the columnar alignment of highly viscous liquid crystals.

Temperature dependence of infrared spectra was measured in a hexagonal columnar (Col h ) mesophase for three homologues of a triphenylene mesogen with two terminal carboxylic acids. It was found for all homologues that the band intensity of hydrogen bonded C=O (approx. 1710 cm −1 ), as a carboxylic acid dimer, increases at the isotropic to Col h phase transition on cooling, while the monomeric C=O (approx. 1740 cm −1 ) band decreases. The results strongly indicate that the rotational and translational fluctuations in Col h mesophase is significantly suppressed by the hydrogen bonding interaction and the suppression depends on the spacer length connecting the triphenylene core and carboxylic acid group leading to the modification of mesomorphic thermal stability.

Infrared photo-induced alignment change of liquid crystal domains was investigated for a hexagonal columnar mesophase of liquid crystalline triphenylene derivative. A uniform and anisotropic change of domains was observed when a polarized infrared light corresponding to the wavelength of the absorption band of triphenylene core was irradiated. IR absorption dichroism is induced as a result of the reorientation of triphenylene core part. The texture observation and polarized microscopic FT-IR spectra show that a change of the molecular alignment occurred, and the direction of columns depends on the polarizing angle of an irradiated infrared light. This technique could provide a novel technology to control the columnar alignment of supra-molecular systems.