High cycling stability and well printability poly(3,4‐ethylenedioxythiophene):poly(styrene sulfonate)/multi‐walled carbon nanotube nanocomposites via in situ polymerization applied on electrochromic display

A high cycling stability material and an additive manufacturing method are reported for the fabrication of solid electrochromic devices. The poly(3,4‐ethylenedioxythiophene):poly(styrene sulfonate)/multi‐walled carbon nanotube (PEDOT:PSS/MWCNT) nanocomposites were synthesized via in situ polymerization. A carboxymethyl cellulose gel was used as the ink vehicle for screen printing. The electrochromic (EC) performance of films patterned by screen printing was also examined. The results of characterization indicate that strong interfacial interactions occurred between PEDOT:PSS and the MWCNTs and the MWCNTs formed a network in these conducting polymers film, so the composite was more conductive than pure PEDOT:PSS. Devices containing PEDOT:PSS/MWCNTs were more stable after 1000 cycles, exhibited higher rate of ion exchange and faster increases in current. The composite containing 0.3 wt % MWCNTs also had a 23% higher color contrast (ΔE*) than pure PEDOT:PSS at 2.5 V applied voltages. The EC inks with well printability not only can be used to print large area films, but also can print fine lines and pixel‐type dots in displays. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45943.     

Flexible electrochromic device based on poly (3,4-(2,2-dimethylpropylenedioxy)thiophene)

In this study, the design, fabrication and characterization of a flexible electrochromic device based on indium tin oxide (ITO) coated polyethylene terephthalate (PET) plastic is discussed. The working electrochromic material film was poly (3,4-(2,2-dimethylpropylenedioxy)thiophene) (PProDOT-Me₂), while the counter layer of the device was vanadium oxide titanium oxide (V₂O₅/TiO₂) composite film, which serves as an ion storage layer. A solution type electrolyte was used as the ionic transport layer and was sandwiched between the working and counter layers. The device exhibited tuneable light transmittance between transparent and deep blue color, with a maximum contrast ratio at 580 nm wavelength. Other important properties, such as switching speed, life time, and coloration efficiency have been improved.     

Multilayer electrochromic surfaces derived from conventional conducting polymers: Optical and surface properties

In this study, some kinds of multilayer (double and triple) electrochromic (EC) surfaces were prepared using layer-by-layer (LBL) electrodeposition techniques. Polypyrrole (PPy) was deposited as the first layer and the upper layers were changed. EC characteristics were investigated by spectroelectrochemical measurements. Surface roughness parameters (Root Mean Square-RMS) were determined using atomic force microscopy (AFM) technique. The results showed that different color options may be obtained by altering LBL deposition of EC polymers. Equilibrium water contact angle (ϴ^equ_water) measurements showed that incorporation of hydrophilic poly(3,4-ethylenedioxythiophene) PEDOT in LBL EC surfaces resulted in a decrease in the contact angle. However, the ϴ^equ_water of multilayer films increased with the incorporation of the hydrophobic polycarbazole (PCarb) layer.     

Solid-state electrochromic devices using pTMC/PEO blends as polymer electrolytes

Flexible, transparent and self-supporting electrolyte films based on poly(trimethylene carbonate)/poly(ethylene oxide) (p(TMC)/PEO) interpenetrating networks doped with LiClO₄ were prepared by the solvent casting technique. These novel solid polymer electrolyte (SPE) systems were characterized by measurements of conductivity, cyclic voltammetry, differential scanning calorimetry and thermogravimetry.The incorporation of solid electrolytes as components of electrochromic devices can offer certain operational advantages in real-world applications. In this study, all-solid-state electrochromic cells were characterized, using Prussian blue (PB) and poly-(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT) as complementary electrochromic compounds on poly(ethyleneterphthalate) (PET) coated with indium tin oxide (ITO) as flexible electrodes. Assembled devices with PET/ITO/PB/SPE/PEDOT/ITO/PET “sandwich-like” structure were assembled and successfully cycled between light and dark blue, corresponding to the additive optical transitions for PB and PEDOT electrochromic layers. The cells required long cycle times (>600 s) to reach full color switch and have modest stability towards prolonged cycling tests. The use of short duration cycling permitted the observation of changes in the coloration-bleaching performance in cells with different electrolyte compositions.     

Self-supported semi-interpenetrating polymer networks for new design of electrochromic devices

This paper reports the preparation of conducting films combining linear poly(3,4-ethylenedioxythiophene) (PEDOT) and cross-linked polyethylene oxide (PEO) into semi-interpenetrating networks. Due to the synthetic pathway, PEDOT is distributed within the PEO matrix and specifically along the two outer faces of the film. Such a distribution of the conducting polymer inside the matrix leads to the design of a self-supported and symmetrical PEDOT-Polymer electrolyte-PEDOT electrochromic device which can substitute the usual multilayer configuration. Optical contrast ΔT_630 nm (%) up to 33% is reached without contrast loss after 1500 switches. The switching time is 30 s for bleaching with a good memory effect (less than 1% decrease of transmittance after 1 h) of the device.     

Truly solid state electrochromic devices constructed from polymeric ionic liquids as solid electrolytes and electrodes formulated by vapor phase polymerization of 3,4-ethylenedioxythiophene

Using polymeric ionic liquids, namely poly[1-(2-(2-(2-(methacryloyloxy)ethoxy)ethoxy)ethyl)-3-methylimidazolium]bis(trifluoromethylsulfonyl)imide or tetracyanoborate, and poly(3,4-ethylenedioxythiophene) (PEDOT) as an ion conductor and electrodes, respectively, the all-polymer-based thin-film symmetrical electrochromic devices (ECDs) have been constructed and tested. The proposed architecture serves as a prove of concept that polymeric ionic liquids (PILs) can be themselves used as solid electrolytes thus avoiding any electrolyte leakage since the ionic liquid species are grafted on the polymer backbone. Three different methods for the synthesis of PEDOT electrode films, including two new approaches consisted in vapor phase polymerization of 3,4-ethylenedioxythiophene (EDOT) in the presence of ionic monomer and poly(ethylene glycol)(di)methacrylates, have been investigated. Two oxidants, Fe[(CF₃SO₂)₂N]₃ and Fe[(CN)₄B]₃, bearing the same anions as PILs were prepared for the first time and utilized in the vapor phase polymerization of EDOT. It was found that the more compact structure and the highest conductivity are achieved for PEDOT electrodes prepared by vapor phase polymerization of EDOT in the presence of ionic monomer and poly(ethylene glycol)(di)methacrylates, followed by radical polymerization of the latters. The simplicity of ECDs assembly, their fast switching times (3–5 s), high coloration efficiency (up to 430 cm²/C), satisfactory optical contrast (up to 28.5%), absence of any liquids and good performance in air and in vacuum were found among the advantages of the proposed technology.     

A simplified all-polymer flexible electrochromic device

New all-polymeric simplified electrochromic devices have been prepared based in an intrinsically conductive polymer, poly(ethylene dioxythiophene) (PEDOT). In these devices PEDOT acts simultaneously as electrochromic layer and current collector layer simplifying the construction of the classic devices from seven to five layers. The device presents a chromatic contrast in all the visible range with a maximum at 650 nm (ΔT=0.15) between 0 and 3 V. Representative bleaching and coloring times are 20 and 16 s, respectively, for  cm devices. The originality of this work is that advanced electrochromic devices can be constructed using commercially available materials and using simple experimental methods.     

Fast electrochemistry of conductive polymer nanotubes: synthesis, mechanism, and application

Conductive polymers exhibit several interesting and important properties, such as metallic conductivity and reversible convertibility between redox states. When the redox states have very different electrochemical and electronic properties, their interconversion gives rise to changes in the polymers' conformations, doping levels, conductivities, and colors, useful attributes if they are to be applied in displays, energy storage devices, actuators, and sensors. Unfortunately, the rate of interconversion is usually slow, at best on the order a few hundred milliseconds, because of the slow transport of counterions into the polymer layer to balance charge. This phenomenon is one of the greatest obstacles toward building rapidly responsive electrochemical devices featuring conductive polymers. One approach to enhancing the switching speed is decreasing the diffusion distance for the counterions in the polymer. We have found that nanotubular structures are good candidates for realizing rapid switching between redox states because the counterions can be readily doped throughout the thin nanotube walls. Although the synthesis of conductive polymer nanotubes can be performed using electrochemical template synthesis, the synthetic techniques and underlying mechanisms controlling the nanotube morphologies are currently not well established. We begin this Account by discussing the mechanisms for controlling the structures from hollow nanotubes to solid nanowires. The applied potential, monomer concentration, and base electrode shape all play important roles in determining the nanotubes' morphologies. A mechanism based on the rates of monomer diffusion and reaction allows the synthesis of nanotubes at high oxidation potentials; a mechanism dictated by the base-electrode shape dominates at very low oxidation potentials. The structures of the resulting conductive polymer nanotubes, such as those of poly(3,4-ethylenedioxythiophene) (PEDOT) and polypyrrole, can be characterized using scanning electron microscopy and transmission electron microscopy. We also discuss these materials in terms of their prospective use in nanotube-based electrochemical devices. For example, we describe an electrochromic device incorporating PEDOT nanotubes that exhibits an ultrafast color switching rate (<10 ms) and strong coloration. In addition, we report a supercapacitor based on PEDOT nanotubes that can provide more than 80% of its own energy density, even at power demands as high as 25 kW/kg.     

Electrochromic properties of a novel low band gap conductive copolymer

A copolymer of 2,5-di(thiophen-2-yl)-1-p-tolyl-1H-pyrrole (DTTP) with 3,4-ethylene dioxythiophene (EDOT) was electrochemically synthesized. The resultant copolymer P(DTTP-co-EDOT) was characterized via cyclic voltammetry, FTIR, SEM, conductivity measurements and spectroelectrochemistry. Copolymer film has distinct electrochromic properties. It has four different colors (chestnut, khaki, camouflage green, and blue). At the neutral state λ_max due to the π-π^* transition was found to be 487 nm and E_g was calculated as 1.65 eV. Double potential step chronoamperometry experiment shows that copolymer film has good stability, fast switching time (less than 1 s) and good optical contrast (20%).An electrochromic device based on P(DTTP-co-EDOT) and poly(3,4-ethylenedioxythiophene) (PEDOT) was constructed and characterized. The device showed reddish brown color at −0.6 V when the P(DTTP-co-EDOT) layer was in its reduced state; whereas blue color at 2.0 V when PEDOT was in its reduced state and P(DTTP-co-EDOT) layer was in its oxidized state. At 0.2 V intermediate green state was observed. Maximum contrast (%ΔT) and switching time of the device were measured as 18% and 1 s at 615 nm. ECD has good environmental and redox stability.     

Aqueous in-situ electrosynthesis and electrochromic performance of PEDOT:PSS/Reline film

Poly(3,4-ethylene dioxythiophene) (PEDOT) is a promising electrochromic material in many practical application, such as smart windows and displays. However, there are still difficulties in currently realizing green manufacturing, high coloration efficiency, and rapid response. Herein, in-situ electrochemical polymerization of PEDOT:PSS/Reline films was suggested in aqueous solution. Deep eutectic solvents (DES) composed of choline chloride and urea (Reline) were employed as green solvents in reaction system and used as dopants for the PEDOT:PSS. The as-prepared PEDOT:PSS/Reline films exhibited remarkable electrochromic properties, including great ion diffusion coefficient, fast reaction time (coloration response time was 1.4 s), prominent transmittance modulation (38%), high coloration efficiency (223 cm²/C) and excellent cyclic stability. Impressively, doping of Reline cannot only provide a green polymerization environment, but also significantly boost the electrochromic properties.     

Molecular assembled self-doped polyaniline copolymer ultra-thin films

A self-assembly technique and copolymerization were used to buildup a self-doped polyaniline (SPANI) ultra-thin film on an indium-tin oxide (ITO) substrate. The monomers used were aniline and its derivative MSAN (m-aminobenzenesulfonic acid). Successful MSAN/AN copolymerization and film formation were simultaneously performed in aqueous solution with the addition of oxidant (APS, ammonium persulfate). The film deposition rate of a high AN/MSAN ratio system is generally higher than that of a low AN/MSAN ratio system. Cyclic voltammetry, UV-vis spectroscopy, and α-step instruments indicate a systematic dependence of the film thickness of these ultra-thin films on the assembly time and temperatures. The Auger depth profile reveals the elemental distribution in these films and exhibits different deposition rates between AN and MSAN. XPS N_1s spectra also show the variation of the degree of doping. This SPANI film can be used as an electrochromic electrode in a corresponding device. Carboxyl-terminated-butadiene-acrylonitrile (CTBN) blended with LiClO₄ was used as a solid polymer electrolyte. A total solid electrochromic device was assembled as ITO/SPANI/LiClO₄-CTBN/PEDOT:PSS/ITO, where PEDOT:PSS is poly(3,4-ethylenedioxythiophene)/poly(4-styrenesulfonate) as the counter complementary electrode. The device was pale gray at −1.5 V and blue at +1.5 V.     

Polypyrrole/MWCNT‐gr‐PSSA composite for flexible and highly conductive transparent film

This study compares the properties of a highly conductive polymer based on polypyrrole and multiwall carbon nanotubes (MWCNTs) grafted with poly (styrenesulfonic acid) (PPy/MWCNT‐gr‐PSSA) prepared for flexible indium tin oxide‐free organic solar cell (OSC) anode with those of PH500 poly(3,4‐ethylenedioxythiophene) : poly(styrenesulfonate) (PEDOT : PSS) in various solvents. Hydrophilic poly(styrenesulfonic acid) (PSSA) was grafted on the MWCNT surfaces to improve dispersion of the MWCNT in an aqueous solution. MWCNT‐gr‐PSSA was added because MWCNT acts as a conductive additive and a template for the polymerization of PPy. Polymerization yields increased as the amount of MWCNT‐gr‐PSSA increased and reached a maximum when 50% of MWCNT‐gr‐PSSA was added. The conductivity of PPy/MWCNT‐gr‐PSSA composite was further improved and the value reached ～ 152 S/cm with the addition of a toluenesulfonic acid (TSA)/HCl dopant mixture. To prepare a flexible OSC anode, PPy/MWCNT‐gr‐PSSA dissolved in solvent mixture, was coated onto a polyethylene terephthalate (PET) substrate. PPy/MWCNT‐gr‐PSSA was dissolved in a mixture of solvents including DMSO, NMP, EG, DEG, and glycerol of a high boiling point that was spin coated onto the PET, then annealed for 30 min at various temperatures. The conductivity of PPy/MWCNT‐gr‐PSSA was further enhanced with solvent treatment and annealing at temperature ranges of 100–175°C. Under optimum conditions, the conductivity and transmittance of PPy/MWCNT‐gr‐PSSA on PET reached 602 S/cm and 84% at 550 nm, respectively. In addition, it was confirmed that the energy level and mechanical strength of the film were suitable for OSC electrode use. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Comparison of the thermally stable conducting polymers PEDOT, PANi, and PPy using sulfonated poly(imide) templates

We showed that it is possible to use sulfonated poly(amic acid)s (SPAA) to template polymerize 3,4-ethylenedioxythiophene (EDOT) to PEDOT, resulting in an aqueous dispersion of conducting polymer. This study compares PEDOT with poly(aniline) (PANi) and poly(pyrrole) PPy using the same and another, more rigid, poly(amic acid) template. A variety of system parameters, including reaction time, conductivity, and overall thermal stability, were noted to change systematically depending on the systems chosen. PANi-SPAA takes less than one tenth of the reaction time of PEDOT-SPAA (12 h versus 7 days), and results in higher conductivities at room temperature (ca. 10 S/cm). However, it is not as thermally stable as the PEDOT-SPAA system; conductivity is not measureable after annealing at 300 °C. PPy-SPAA was found to be more thermally stable than PANi-SPAA (less mass lost at 300 °C), but it was still more conductive than un-doped PEDOT-SPAA by a factor of 1000 (ca. 1.0 S/cm).     

Conductive polypyrrole nanofibers via electrospinning: Electrical and morphological properties

Conductive polypyrrole nanofibers with diameters in the range of about 70-300 nm were obtained using electrospinning processes. The conductive nanofibers had well-defined morphology and physical stability. Two methods were employed. Electrospun nanofibers were prepared from a solution mixture of polypyrrole (PPy), and poly(ethylene oxide) (PEO) acted as a carrier in order to improve PPy processability. Both the electrical conductivity and the average diameter of PPy nanofibers can be controlled with the ratio of PPy/PEO content. In addition, pure (without carrier) polypyrrole nanofibers were also able to be formed by electrospinning organic solvent soluble polypyrrole, [(PPy3)⁺ (DEHS)⁻]_x, prepared using the functional doping agent di(2-ethylhexyl) sulfosuccinate sodium salt (NaDEHS) [Jang KS, Lee H, Moon B. Synth Met 2004;143:289-94. [24]]. Electrospun blends of sulfonic acid (SO₃H)-bearing water soluble polypyrrole, [PPy(SO₃H)-DEHS], with PEO acting as a carrier, are also reported. The factors that facilitate the formation of electrical conduction paths through the electrospun nanofiber segments are discussed.     

Transparent conductive film based on carbon nanotubes and PEDOT composites

Single-walled nanotubes (SWNTs), thin multiwalled carbon nanotubes (t-MWNTs) and multiwalled carbon nanotubes (MWNTs) were treated with H₂SO₄–HNO₃ acid solution, under different chemical conditions. The acid-treated CNTs were dispersed in DI water and in poly (3,4-ethylenedioxythiophene) (PEDOT) solution. Furthermore, the finely dispersed CNTs/PEDOT solutions were employed to a simple method of bar coating to obtain the transparent conductive films on the glass and polyethylene terephthalate (PET) film. A sheet resistance of 247 Ω/sq and a transmission of 84.7% were obtained at a concentration of the acid-treated CNTs of 0.01 wt.%.     

PPy modified 1T-MoS2 hollow spheres with cohesive architecture as high-performance anode material for Li-ion batteries

A cohesive architecture of 1T-MoS₂ covered by PPy composite (1T-MoS₂@PPy) is successfully fabricated by a simple hydrothermal reaction followed by an in-situ polymerization route. The composite material consists of 1T-MoS₂ hollow microsphere and conductive PPy coating layer. The cohesive architecture enables the composite to show rapid shuttle of electrons/lithium ions and good ductility to buffer the volume changes during charging and discharging process when it is used as anode material. As expected, 1T-MoS₂@PPy composite exhibits a favorable discharge capacity up to 970.3 and 407.1 mAh g^?1 at 0.2 and 3 A g^?1, respectively. In addition, the composite also achieves impressive cycling performance of 717.1 mAh g^?1 at 1 A g^-1 after 500 cycles. This study provides a meaningful guidance in rational design of anode materials with cohesive architecture as well as high electrochemical performance.     

Preparation and electrochemical performance of modified Ti3C2Tx/polypyrrole composites

MXenes with a large surface area have been widely studied to improve the pseudocapacitance of electrode materials by combining conductive polymer materials. In this article, a superficial strategy to enhance the electrochemical properties by in situ polymerization of a pyrrole monomer between the Ti₃C₂T_x layers modified with 1,5-naphthalene disulfonic acid (NA) and cetyltrimethylammonium bromide (CTAB) was investigated. It is found that polypyrrole (PPy) and Ti₃C₂T_x can be combined through strong interactions between each other, and the specific capacitance of the modified Ti₃C₂T_x/PPy composite was increased to a maximum value of 437 F g⁻¹, which was more than thrice higher than that of pure PPy. The composite also exhibited good cycling performance (76% capacitance retention after 1000 cycles). Moreover, owing to the synergistic effect between the PPy and Ti₃C₂T_x layers, the composite provided better electron or ion transfer and surface redox processes than that of pure PPy, which indicated that this composite can be used as a promising electrode material for supercapacitors. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47003.     

Multifunctional fiberglass-reinforced PMMA-BaTiO3 structural/dielectric composites

Fiberglass-reinforced polymer composites were investigated for potential use as structural dielectrics in multifunctional capacitors that require simultaneous excellent mechanical properties and good energy storage characteristics. Composites were fabricated employing poly(methyl methacrylate), PMMA, as the structural matrix. While barium titanate (BaTiO₃) nanopowder was added to the composites for its high room temperature dielectric constant, fiberglass was employed to confer high stiffness. A conductive polymer blend of poly (3,4-ethylenedioxythiophene) and polystyrene sulfonate (PEDOT:PSS) was used to coat the BaTiO₃ nanoparticles with the purpose of further elevating the dielectric constant of the resultant PMMA-composites. FTIR spectroscopy, TGA and SEM measurements were conducted to prove the successful coating of BaTiO₃ nanoparticles with the PEDOT:PSS blend. TEM measurements revealed a good dispersion of coated nanoparticles throughout the PMMA matrix. The fiberglass-reinforced-PMMA composites containing neat and coated BaTiO₃ were found to exhibit excellent stiffness. In addition, the use of PEDOT:PSS in conjunction with BaTiO₃ was observed to improve the dielectric constant of the composites. Finally, the dielectric constant of the structural composites was found to vary only slightly with temperature.     

Electropolymerization kinetic study of 3,3-dimethyl-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepine and its optical optimization for electrochromic window applications

Poly (3,3-dimethyl-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepine), PProDOT-Me₂, is one of the most promising conducting polymers in the alkylenedioxythiophene based family for electrochromic window applications. In the electropolymerization kinetic study of 3,3-dimethyl-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepine (ProDOT-Me₂), microgravimetry and chronoamperometry were used to determine the reaction orders with respect to the electrolyte and monomer, and the corresponding general kinetic equation of electropolymerization. This study presents that monomer concentration has a strong impact on electropolymerization mechanism. The relationship between film thickness and polymerization time was analyzed indicating that saturation of polymerization reduced the increase rate of film thickness with polymerization time. Also, the electropolymerization conditions were optimized to reach high contrast (Δ%T > 70%) with the minimum of transmittance (%T_min < 1) for electrochromic window applications.     

Gel electrolytes with ionic liquid plasticiser for electrochromic devices

The comparative performance of conducting polymer electrochromic devices (ECDs) utilising gel polymer electrolytes (GPEs) plasticised with ethylene carbonate/propylene carbonate or (N-butyl-3-methylpyridinium trifluoromethanesulphonylimide (P₁₄TFSI) has been made. Lithium perchlorate and lithium trifluoromethanesulphonylimide salts were used in the GPEs to provide enhanced ionic conductivity and inhibit phase separation of the polyethyleneoxide (PEO) and plasticiser. ECDs were assembled from cathodically colouring, polyethylenedioxythiophene (PEDOT), and anodically colouring, polypyrrole (PPy), conducting polymer electrochromes deposited by vapour deposition. The photopic contrast switching over the visible light spectrum, switching speeds and device stability of the ECDs were obtained. These studies demonstrate that the ionic liquid (IL) plasticised GPEs are a suitable replacement for pure IL based devices and volatile organic solvent plasticisers based upon ethylene carbonate/propylene carbonate mixtures.