Electrolyte and solvent effects in PPy/DBS linear actuators
Introduction
The properties of conducting polymer linear actuators have been examined over the past 20 years [1], [2], [3]. Polypyrrole (PPy) and poly(3,4-ethylenedioxythiophene) (PEDOT) free-standing films were shown to actuate owing to anion, cation and mixed ion fluxes under reversible redox cycles [4], [5], [6]. Linear strains for PPy/LiTFSI [7] and PPy/TBACF3SO3 [8] in the range of 12–30% were reported, but also high strain fatigues in most films after continuous cycling [9]. In the case of PEDOT/TBACF3SO3 linear actuators, it was shown that the polymerization process, and in particular the polymerization potential, influences which ion dominates the actuation properties [10]. With potentiostatic polymerization (E = 1.1 V) mainly cation-driven actuation was found in both organic and aqueous electrolytes. To explain this effect the spherical form of the CF3SO3− anion was taken in account, and suggested to be responsible for the CF3SO3− being immobile within the PEDOT network [4]. PPy/DBS actuators have been considered as cation-driven actuators due to the immobile DBS− ion incorporated during electropolymerization and leading to volume increases during reduction [11]. Recent research showed a mixed ion influence in the linear actuation properties of PPy/DBS-PVdF trilayer actuators [12]. Fuchiwaki et al. recently investigated PPy/para-phenolsulfonic acid free standing films glued with a tape forming a bilayer artificial muscle. The ion exchange properties were studied in different electrolytes, where anion movement was observed in the case of NaPF6 with two times higher bending in comparison with NaCl, where dual ion movement was observed (Na+ insertion upon reduction and Cl− insertion upon oxidation) [13].
To have movement of only one ion type (anions or cations with solvent molecules) at anodic or cathodic potentials to dominate the actuation has been a major goal in the development of CP actuators. Synthesis temperature, electrolyte, polymerization conditions (i.e. galvanostatic, potentiostatic and potentiodynamic) and different solvents [14], [15], [16] have been investigated. However, the reasons why on occasions anion, cation or mixed-ion actuation occurs are not fully understood. A model that fits most of the charging/discharging properties of CPs, explaining anion and cation effects, is the electrochemically stimulated conformational relaxation (ESCR) model [17], [18], [19]. According to the model, ions are inserted in the CP film during redox reactions causing volume changes. During oxidation the polymer structure opens via conformational changes of the chains and ion channels are formed [18].
In this research PPy was polymerized at low temperature in a DBS solution and subsequently actuated in an organic (TBACF3SO3, PC) and an aqueous (TMACl) electrolyte under ECMD measurements. The goal was to evaluate what changes in actuation occur when the electrolyte and solvent changes. The PPy properties were studied before and after actuation using Raman spectroscopy, scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). An in-house built characterization system, developed in the Polymer Electronics Research Centre laboratory, based on scanning ion conductance microscopy (SICM) [20], [21], was applied to evaluate how the electronic properties at the film surface change before and after actuation in different electrolytes.
Section snippets
Materials
Sodium dodecylbenzenesulfonate (NaDBS, 99%), propylene carbonate (PC, 99%), tetrabutylammonium trifluoromethanesulfonate (TBACF3SO3, 99%), tetramethylammonium chloride (TMACl, 99%), ethylene glycol (EG, 99.8%) were obtained from Sigma–Aldrich and used as supplied.
PPy/DBS electropolymerization
PPy/DBS was deposited galvanostatically (0.2 mA cm−2) on stainless steel working electrodes (surface area 5.4 cm2) in a three electrode cell (with a platinum sheet counter electrode and a Ag/AgCl wire reference electrode, 0.52 V vs. SHE),
Polymerization of PPyDBS on stainless steel
The potential–time curve, Fig. 1, records the PPy/DBS deposition under galvanostatic conditions with an initial drop in potential at the beginning of the polymerization, followed by an increase in the potential from 0.6 V to 0.72 V. The low value of the potential indicates uniform deposition of PPy on the stainless steel substrate [24].
ECMD measurements.
Cyclic voltammetric measurements for PPy/DBS free-standing films were performed in parallel with ECMD measurements to evaluate the linear actuation of the film
Conclusions
PPy doped with DBS− free standing films are expected to show mainly cation-driven actuation due to the DBS− anions immobilized during the polymerization process. Nevertheless a rare phenomenon was observed where the progressive ion mobility changed, matching the size and mobility of the anions and cations, seen during square wave potential step experiments (300 steps), and the direction of mainly cation-driven actuation changed to mainly anion-driven actuation during cycling. The anion driven
Acknowledgements
This research was supported by the European Union through the European Social Fund (MTT76), the European Scientific Network for Artificial Muscles (ESNAM, ECOST-STSM-MP1003) and partly through the New Zealand Foundation for Science and Technology (New Economy Research Fund, contract no. UOAX0408).
Nihan Aydemir was born in Turkey and currently doing her PhD work at University of Auckland under supervision of Prof. J. Travas-Sejdic and Prof. David Williams. She has received her bachelor's degree in chemistry and master's degree in polymer science and technology at Istanbul Technical University. Her research interests cover nano/micro fabrication of conducting polymers, label free electrochemical biosensors and developing highly localized surface characterization techniques with using
References (35)
- et al.
Performance and work capacity of a polypyrrole conducting polymer linear actuator
Synth. Met.
(1997) - et al.
Cation driven actuation for free standing PEDOT films prepared from propylene carbonate electrolyte containing TBACF3SO3
Electrochim. Acta
(2008) - et al.
Mixed-ion linear actuation behavior of polypyrrole
Electrochim. Acta
(2007) - et al.
Effect of polymerization potential on the actuation of free standing poly-3,4-ethylenedioxythiophene films in a propylene carbonate electrolyte
Electrochim. Acta
(2010) - et al.
Electrochemistry of interlayer supported polypyrrole tri-layer linear actuators
Electrochim. Acta
(2014) - et al.
Enhancement of the electrical conductivity of polypyrrole film by stretching: Influence of the polymerization conditions
Synth. Met.
(1990) - et al.
Effects of monomer and electrolyte concentrations on actuation of PPy(DBS) bilayers
Synth. Met.
(2005) - et al.
The application of nanopipettes to conducting polymer fabrication, imaging and electrochemical characterization
Prog. Polym. Sci.
(2012) - et al.
Ion movement in polypyrrole/dodecylbenzenesulphonate films in aqueous and non-aqueous electrolytes
Solid State Ionics
(2002) - et al.
Actuation of polypyrrole films in propylene carbonate electrolytes
Sens. Actuator B
(2007)
Raman spectra of polypyrrole and its 2,5-13C-substituted and C-deuterated analogues in doped and undoped states
Synth. Met.
Conducting polymer electrochemical actuator made of high-strength three-layered composite films of polythiophene and polypyrrole
Sens. Actuators B
In situ cyclic voltammetry-surface-enhanced Raman spectroscopy: studies on the doping-undoping of polypyrrole film
Thin Solid Films
Spectroscopic studies of doping reactions in polypyrrole actuators
Curr. Appl. Phys.
A conducting polymer artificial muscle with 12% linear strain
Adv. Mater.
Highly stretchable and powerful polypyrrole linear actuators
Chem. Lett.
Cyclic step-voltammetric analysis of cation-driven and anion-driven actuation in polypyrrole films
Jpn. J. Appl. Phys.
Cited by (46)
Future potential for lithium-sulfur batteries
2023, Journal of Power SourcesGaining insight into electrolyte solution effects on the electrochemomechanical behavior of electroactive PU/PPy nanofibers: Introducing a high-performance artificial muscle
2020, Sensors and Actuators, B: ChemicalCitation Excerpt :In the artificial muscles made of conductive polymers, the specifications of electrolyte solution in which the artificial muscle will be placed under electrical stimulation can greatly impact the electrochemical actuation results. Although there are some research works on the contribution of electrolyte solution to the performance of artificial muscles made of polymeric films [40–43], to our knowledge, there is no literature on the effect of electrolyte solution specifications on the conductive polymer-based nanofibrous artificial muscles. In this study, a combination of electrospinning and in-situ chemical polymerization using different dopants was considered to produce nanofibrous PU/PPy bending artificial muscles.
The response of polypyrrole–DBS electrochemical molecular motors to Na concentration: Analogies in cell biology
2019, Electrochemistry CommunicationsCitation Excerpt :The working electrode (WE) was a platinum plate with a surface area of 1 cm2 and the counter electrode (CE) was a 2 × 5 cm stainless-steel plate. The polypyrrole (DBS) films were electrogenerated galvanostatically [29,30] as thin films covering a Pt sheet using a flow of current density 2 mA cm−2 for 300 s on a clean Pt electrode (WE) with 1 cm2 of total surface area submerged in fresh 0.1 M Py and 0.1 M DBSA aqueous solution at room temperature. The conditions were similar to those used to produce the anion-exchanging polypyrrole thin films on which the aforementioned theoretical model was based [19–21,31].
Polypyrrole doped with dodecylbenzene sulfonate as a protective coating for copper
2018, Electrochimica Acta
Nihan Aydemir was born in Turkey and currently doing her PhD work at University of Auckland under supervision of Prof. J. Travas-Sejdic and Prof. David Williams. She has received her bachelor's degree in chemistry and master's degree in polymer science and technology at Istanbul Technical University. Her research interests cover nano/micro fabrication of conducting polymers, label free electrochemical biosensors and developing highly localized surface characterization techniques with using Scanning Ion Conductance Microscope (SICM).
Paul Kilmartin is a Professor in the School of Chemical Sciences at the University of Auckland. He completed a PhD in the electrochemistry of polyanilines at the same University in 1997 and joined the academic staff soon after. His research interests have diversified to include the characterization antioxidants in beverages such as wines, and projects on conducting polymers within the Polymer Electronics Research Centre, including the development of electrochemical sensors, antioxidant packaging and work with actuators.
Jadranka Travas-Sejdic is a Professor in Macromolecular Sciences at the School of Chemical Sciences at the University of Auckland (New Zealand). Her current research is in the field of advanced polymeric materials for health, bioelectronics and polymer electronic devices with projects including development of novel gene sensors, conducting polymers-based switchable surfaces, biointerfaces and actuators. She is a Fellow of the International Union of Pure and Applied Chemistry and the New Zealand Institute of Chemistry, and a Councilor of the Pacific Polymer Federation.
Arko Kesküla is a PhD student at University of Tartu (IMS lab) with main focus on polymeric ionic liquids as membranes for electrochemical actuators under supervision of Dr. A.-L. Peikolainen and Prof. Uno Mäeorg. He received his master degree 2012 at University of Tartu in material science.
Anna-Liisa Peikolainen obtained her PhD degree in 2011 in chemistry at Tallinn University of Technology. Her main research topic was nanoporous organic aerogels. Organic aerogel being one of the sources of high surface area carbon led her to field of carbon based actuators. Since 2012 she is a Material Research Scientist at University of Tartu at Intelligent Materials and Systems Lab focusing on carbon–polymer composites and carbon based actuators.
James Parcell enrolled 2001 his bachelor studies in physics at Otago University (New Zealand) and received his master in Mechatronics at University Auckland 2012. Now he is developing software for scanning, weighing, dimensioning systems for freight, food, chemical and concrete industries based in Brisbane.
Madis Harjo finished his bachelor's degree in Tallinn University of Technology in 2012. Starting from 2012 he is doing his master thesis in University of Tartu (IMS lab) under supervision of Dr. Martin Järvekülg and Prof. Rudolf Kiefer. His main works includes cell activation with glucose-gelatine fiber mat with embedded actuators.
Alvo Aabloo received his PhD in solid state physics in 1994 from University of Tartu. Since 2007 he is a Professor in the Institute of Science and Technology, University of Tartu and the Head of Intelligent Materials and Systems Laboratory. His current research interests include atomistic and multi scale modeling of polymer electrolytes and their interfaces, radiation damage studies, electromechanically active polymer transducers based on ionic electroactive polymers and their applications in robotics and micro devices.
Rudolf Kiefer received his diploma in chemistry (MSc) from University of Freiburg, (Germany) in 1999 and his PhD degree (conducting polymers for micro actuators) in micro system techniques from Freiburg University (Germany) in 2005. He made his post doc at the Polymer Electronic Research Centre (PERC) of University of Auckland, New Zealand and worked in Industrial Technology Research Institute in Hsinchu, Taiwan as a Researcher. Since 2012 he is Visiting Professor in material technology at University of Tartu, Institute of Science and Technology (Estonia). His main research interest includes characterization and applications in electro active polymers.