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Herein, we present a facile method for color-tuning an electrochromic device that switched between two neutral colors through simple color mixing of a conjugated polymer, poly(2,2-dimethyl-3,4-propylenedioxythiophene) and an electrochromic small molecule aromatic diester, diethyl-4,4′-biphenyldicarboxylate. The resulting device had a photopic contrast of ca. 57% across the visible spectrum. In addition, the device exhibited color uniformity and stability over 2,000 switches. Using these mixed coloring materials, a large area electrochromic device of 140 cm2 was fabricated, exceeding the size of ophthalmic lenses and small displays.

Herein, we present a versatile way to increase the photopic contrast of electrochromic devices (ECDs), approximately 14%, through the use of binary mixtures of propylene carbonate, diethyl carbonate, and ethylene carbonate that serve the role as plasticizers in the gel electrolyte. The binary plasticizer mixture changed the physical properties of the gel electrolyte medium, including the viscosity and dielectric constant, and also facilitates the diffusion of ions and monomer in the medium leading to an increase in ionic conductivity and the photopic contrast. ECDs were fabricated using a one-step lamination procedure, based on poly(2,2-dimethyl-3,4-propylenedioxythiophene) (PProDOT-Me2) with different polymer gel electrolyte compositions where the electrochromic polymer was electrochemically obtained in situ. Gel electrolytes based on unary or binary plasticizer systems and poly(ethylene glycol) diacrylate (PEG-DA) with varying lithium trifluoromethanesulfonate (LiTrif) loading were investigated for the effect of solvent on ionic conductivity and the resulting photopic contrast of the ECD. This study demonstrates a relationship between photopic contrast and ionic conductivity, where the system reaches a maximum in photopic contrast the system is also at the maximum ionic conductivity.

Utilizing the in situ method, we report the fabrication of flexible electrochromic (EC) devices in a one-step lamination procedure. In this study, electrochromic device performance was enhanced via the use of new gel polymer electrolyte (GPE) materials based on poly(ethylene glycol) (PEG) derivatives. PEG serves as the polymer matrix in electrochromic devices (ECDs) that provides not only mechanical stability, but also a wide potential window and compatibility with a variety of salts. Poly(ethylene glycol) dimethacrylate (PEGDMA) in conjunction with poly(ethylene glycol) methyl ether acrylate (PEGMA), containing lithium trifluoromethanesulfonate (LiTRIF) as the salt and propylene carbonate (PC) as a plasticizer; we investigated various electrolyte parameters, including salt loading, the mono/di-functional PEG ratio, and the plasticizer to PEG ratio. Optimized gel systems exceed the mechanical flexibility of indium tin oxide (ITO) coated polyethylene terephthalate (PET) substrates in their sustainable minimum bending radius of curvature, exhibit an ionic conductivity up to 1.36 × 10−3 S cm−1, and yield electrochromic devices (ECDs) with photopic contrasts as high as 53% (without background correction) using poly(2,2-dimethyl-3,4-propylenedioxythiophene) (PProDOT-Me2) as the standard electrochromic material. In addition to ionic conductivity, the crosslink density of the GPEs was found to have an important effect on the photopic contrast of the resultant ECDs. Using these results, 110 cm2 flexible patterned EC displays were assembled as a demonstration of their potential in real world applications.

Herein, a study on varying salts and their composition used in the gel electrolyte for a one-step lamination assembly procedure for electrochromic devices was carried out to explore their effects on various electrochromic performance parameters, such as color uniformity, photopic contrast, switching speed, and optical memory. Electrochromic polymers formed in different gel electrolyte compositions are highly dependent on the type, amount, and composition of salt used. The following groups of salts were investigated: ionic liquids, ammonium salts, and lithium salts. The lithium salts yielded devices with the best color uniformity, photopic contrast as high as 48%, and switching response speeds as low as 1 s for 5.5 cm2 devices using the electroactive monomer 2,2-dimethyl-3,4-propylenedioxythiophene (ProDOT-Me2) to generate the electrochromic polymer. Hermetically sealed electrochromic devices exhibited optical memory of 27 h for a 2% photopic transmittance loss under normal laboratory conditions, and a 171 cm2 electrochromic device was demonstrated.

Electrochromic fabric devices represent a further extension to the plethora of available literature on conductive fabrics. This article contains a brief overview of electrochromic devices, electrochromic polymers, conductive materials, conductive fabrics, and electrochromic fabric devices. A tabulated list of the perceived colour of a number of electrochromic polymers that is contained herein is designed to serve as an aide to colour mixing studies. The challenges of optimisation and commercialisatiion of electrochromic fabric devices and their mitigating factors are conjectured, along with some future potential applications for electrochromic fabric device technologies.

Herein we report the synthesis of a new class of processable siloxane precursor polymers consisting of aromatic groups and flexible siloxane linkages and their conversions to green and blue electrochromic polymers in the solid state. 3,4-Ethylenedioxythiophene (EDOT), 2,2′-bis(3,4-ethylenedioxythiophene) (BiEDOT), and a donor–acceptor moiety 4,7-bis(EDOT)-2,1,3-benzothiadiazole (BEBTD) were incorporated as aromatic groups to demonstrate the versatility of the precursor method to different aromatic systems. The utilization of a siloxane linkage allows for a precursor polymer exhibiting improved solubility in common organic solvents and accessible glass transition temperatures (−1 to 132 °C) as compared to a previously reported silane precursor. A simple method to control the thermal properties of the precursor was also demonstrated by incorporation of both siloxane and silane functionalities into the precursor backbone. The oxidatively converted product from the precursors showed electronic and optoelectro...

The colour of electrochromic fabric, and its colour transitions, was explored on the basis of variations in underlying fabric colour. A complete understanding of this phenomenon is essential for the fabric’s use in full-colour wearable displays or other applications. Previous work in this area utilised only white-coloured starting materials. Herein, a large colour swathe of fabrics was chosen. They were loaded with the commercially available conducting polymer, PEDOT-PSS, and were coated with an electrochromic polymer. These all-organic substrates were then switched between their two coloured states via reversible oxidation and reduction. At every stage, coordinates in the CIE Lu′v′ colour space were measured. It was found that darker colours decrease the overall contrast of the electrochromic, with black being entirely unobservable. More vibrant colours affected the observed colour through a subtractive mixing effect, as expected, but no adverse contrast effects between the two states of the electrochromic system was observed.

A stretchable e-textile was fabricated by simply soaking Spandex fabric in a conductive polymer aqueous dispersion, PEDOT-PSS. The resulting conductive fabric had an average conductivity of 0.1 S/cm. Subjecting the fabric to more than one soaking step increased the conductivity of the fabric up to ca. 2.0 S/cm resulting in a 33% faster switching speed. This simple methodology is not limited to Spandex (50% nylon/50% polyurethane). Several other fabric compositions were investigated for their conductivity via this process, including 100% cotton, 60% cotton/40% polyester, 95% cotton/5% Lycra, 60%polyester/40% rayon, 100% polyester, and 80% nylon/20% Spandex, listed in order of decreasing hydrophilicity. Those fabrics with higher water uptake resulted in higher conductivities upon soaking in PEDOT-PSS. Electrochromic polymers coated on the fabric could be switched between their different colored states, even upon stretching of the Spandex. SEM revealed that the electrochromic polymer coated on the substrate separated under stretching, uncovering the color of the base conducting fabric. It was found that the PEDOT-PSS was not a film on the Spandex but rather homogenously dispersed nanoparticles within the fabric matrix forming a percolated network.

Herein we describe a method for the preparation of solid-state devices without the need for solution-based conversion or deposition steps. Precursor polymers are converted to their conjugated, electrochromic counterpart inside assembled solidstate devices; we refer to this process as in situ conversion. There are three main advantages to this method. First, we have shown that the previously required clean and defect-free substrates are not necessary for in situ conversion. Therefore, neither a rigorous cleaning step nor pristine processing environments are needed for device assembly. This is particularly advantageous for large-area applications where the probability of defects increases with the size of the substrate and thus windows or other such devices would benefit greatly from this method. Second, we have eliminated the solution step in the device preparation process. This step could be either electrodeposition or electrochemical conversion of a precursor system in an electrolyte bath. In situ conversion eliminates the need for this costly and wasteful step by preparing the conjugated material inside a solid-state device. Thus, there is no need for the disposal of toxic organic solvents and salt systems. Finally, devices prepared by in situ conversion retain the entirety of the precursor material used. No leeching of monomer or oligomer into the discarded electrolyte occurs because the process is contained within a sealed solid-state device. In situ conversion would be useful in the preparation of a myriad of devices which utilize conjugated polymers in conjunction with redox processes, such as capacitors, sensors, drug delivery applications, thin film transistors, and electrochromics, among others. Figure 1 shows images and chemical structures for an assembled, in situ solid-state device at each stage of this method. The precursor polymer approach to conjugated polymers is attractive in its own right. Precursor polymers are soluble materials which can be converted to conjugated polymers after deposition on a substrate. Herein, we utilize copolymers of aromatic and silane units. Oxidative conditions cause cleavage of the Si–C bonds and subsequent coupling of the aromatics to form the conjugated electrochromic. This approach allows for the incorporation of a variety of electroactive monomers in different ratios into the final conjugated backbone, something not always feasible by electrodeposition. Many different approaches to addressing solubility have been explored, typically relying on alkylor alkoxy-substitution. These approaches could be limited in terms of industrial processing due the rigidity of the polymeric backbone, which results in high glass transition temperatures (Tg) despite their solubilizing units. We have made use of precursor polymer systems, whereby a copolymer with an alkyl-substituted silane or siloxane is used. Alternatively, a pendant chromophore on a solubilizing norbornene backbone has been employed. The precursor materials exhibit Tgs ranging from 9 8C to 80 8C. Precursor polymers may be processed by any traditional solution-based method, including ink jet printing, electrostatic spinning, spin coating, spray coating, dip-coating, doctor blading, etc., in addition to non-solution-based methods, such as melt-processing. Previous work has shown the ability to photopattern these precursors, as well. The creation of nanofiber mats of electrochromic materials results in unique morphologies which are controllable and reproducible, something impossible to mimic with electrodeposition. This adds yet another facet to the versatility of in situ conversion. Electrochemical polymerization requires clean and defect-free conductive substrates in order to achieve uniform films due to the nucleation and growth mechanism of deposition. Devices built without clean ITO (using intentionally unclean substrates) were found to undergo in situ conversion without visible defects in the final device, making this method attractive for large-scale processing. In the past, this oxidative conversion has been carried out in a quasi-reusable electrolyte bath resulting in desilylation and coupling of the aromatic units to form the p-conjugated electrochromic material. Afterwards, they were assembled into a device and characterized. We were able to achieve the conversion from a precursor polymer to its conjugated counterpart inside an assembled device, effectively removing the need for any solution steps. This method utilizes an assembled electrochromic sandwich device, which is a two-electrode cell, to achieve the same electrochemistry as a three-electrode cell in solution. The in situ method is not limited only to this device architecture, however. The precursor polymer used for this study is poly(bis[3,4-ethylenedioxythiophene]thiophene-dioctylsilane) (PBEDOT-T-Si[Octyl]2), Tg1⁄4 40 8C, and is a light-yellow colored material when cast as a film. The converted product is a conjugated, electrochromic polymer which switches from a red state when neutral to a blue state when oxidized. The conversion process from a yellow to a blue/red is irreversible. Any such precursor that formed a uniform film upon processing has yielded similar film quality when converted in

Herein we describe the preparation and characterization of reflective-type electrochromic devices using stretchable, conductive fabric electrodes. Two fabrics were used in this study: woven stainless steel mesh and Lycra spandex impregnated with a conducting polymer (poly[3,4-ethylenedioxythiophene]-poly[styrene sulfonate], PEDOT-PSS). Electrochromic polymers were prepared on the surface of these fabric electrodes and devices were assembled. The time taken for the electrochromic polymer to switch between colored states in devices prepared with stainless steel electrodes (conductivity ca. 9,800 S/cm) was ca. 0.3 s, whereas that using PEDOT-PSS loaded Lycra (conductivity ca. 0.1 S/cm) was a few seconds. The iris effect was evaluated for each of the device architectures, showing no effect for steel mesh/steel mesh devices and a propagating front for spandex-based devices. The electrochromic spandex functioned in solution while being stretched. In addition, stenciled devices were built. Such fabric electrochr...

Herein we report the photolithography of electrochromic conjugated polymer (CP) films on the micron scale without exposing the CP to high energy UV radiation. The synthesis of polynorbornene-based precursor copolymers having units with pendant terthiophenes and photocrosslinkable units allows for photopatterning at an earlier stage with respect to the polymerization (chemically or electrochemically) that yields the conducting polymer. The effect that the composition of the photocrosslinkable unit has on the overall process was studied, showing no effect on the electrochemical and optical performance of the conducting polymer. Electrochromic photopatterned structures down to 1 μm were obtained, together with some basic structures for microelectronics. This technique does not have any specific substrate restrictions, and can be used to pattern conducting polymers on flexible, rigid, conducting, or insulating substrates using the present photolithography facilities available to industry and academia.

A new methodology for the electrochemical characterization of any device constituted by two electroactive films of conducting polymers, such as electrochromic windows, artificial muscles, polymeric batteries or supercapacitors, is proposed. During electrochemical characterization of dual polymer devices, the charge consumed by the device and the independent potential evolution vs. a reference electrode (oxidation states) of the two constituent materials are followed. The charges consumed inside and outside the electrochromic potential window of each polymer are measured, therefore obtaining percentages of efficient and inefficient charge. Dual polymer electrochromic systems were constructed and characterized by potential sweeps. The influence of the applied potential limits, the redox charge ratio between the two constituting films, or the starting oxidation state of each material on the final percentage of efficient charge consumed by each electrode were studied.

Polyterthiophene nanostructures consisting of periodic nanolines were prepared using the precursor polymer approach in conjunction with nanoimprint lithography. Precursor polynorbornylenes consisting of terthiophene side chains were prepared from their corresponding norbornylene monomers via ring opening metathesis polymerization. A copolymer consisting of terthiophene norbornylene and acetate norbornylene repeat units with a 50:50 composition exhibited a glass transition temperature of 52°C. Nanolines of percursor polynorbornylene were prepared by thermal nanoimprint lithography. The nanoimprinted precursor polymer was then converted to conjugated conductive polymer via chemical and electrochemical oxidation of the terthiophene side units. Nanoimprinted lines of conductive polyterthiophene exhibited high electrochromic contrast at 437 nm.

Solid-state electrochromic devices, based on poly-(3,6-bis(2-(3,4-ethylenedioxy)thienyl)-N-methylcarbazole) (PBEDOT-NMCz) and poly((3,4-ethylenedioxy)thiophene) (PEDOT), having 30 cm2 active switching area, low voltage consumption, photopic contrasts of ca. 30% and switching speeds as low as 0.6 s, were prepared and studied. A special design of electrochemical cell allowed us to electrodeposit films of conducting polymer over large areas. Photopolymerization of the gel is a fast and straightforward way to assemble sealed and solid-state devices. Addition of different amounts of plastizicer to a photopolymerizable PEO-based gel electrolyte enhanced switching speed performance over approximately two orders of magnitude. Cyclic voltammetry was shown as a tool to evaluate shorcircuited devices.

A general procedure to calculate the maximum contrast from an electrochromic material is presented. The obtained results were tested by spectroelectrochemical studies of two different conducting polymer films: poly-3, 4-ethylenedioxy-thiophene (PEDOT) and poly-3,6-bis(2-(3,4-ethylenedioxy)thienyl)-N-methylcarbazole (PBEDOT-NMCz). The presented methodology constitutes a useful tool for the optimization of electrochromic devices. Keywords: Conducting polymer, Electrochromism, Maximum contrast, Electrochromic device

Herein we report the synthesis and electrochemical characterization of poly(thieno[3,4-b]thiophene), a new low band gap conducting polymer with a high redox switching stability that exhibits high optical transparency in the semiconductive state. The monomer, thieno[3,4-b]thiophene (T34bT), has a low oxidation potential for polymerization, 1.02 V vs Ag/Ag+ (1.25 V vs SCE), a potential between that for the oxidation of 3,4-ethylenedioxythiopene and pyrrole. Poly(T34bT) has a band gap of ca. 0.85 eV (1459 nm) as determined by the onset for the π-to-π* transition from the UV−vis−NIR spectrum and 0.8 V from the difference in the onsets for both the p- and n-doping processes from cyclic voltammetry. Stability studies as determined from chronocoulometry and chronoabsorptometry indicate that the polymer retains 95% electroactivity and 96% change in optical density after 100 double potential steps. Poly(T34bT) is sky-blue in the reduced form and optically transparent (no observable color) in the oxidized state wit...

A method to color-tune electrochromic devices through the use of theoretical calculations is demonstrated to achieve neutrality using only three monomers that form two distinct copolymers. These devices exhibit photopic contrasts up to ca. 38%, high neutrality, color uniformity, and switch speeds of less than 1 s. In addition, this method is used to fabricate a large-area flexible electrochromic device of 75 cm(2) , exceeding the size of small displays.

We utilized our in situ method for the one-step assembly of single-layer electrochromic devices (ECDs) with a 3,4-propylenedioxythiophene (ProDOT) acrylate derivative, and long-term stability was achieved. By coupling the electroactive monomer to the cross-linkable polymer matrix, preparation of the electrochromic ProDOT polymer can occur followed by UV cross-linking. Thus, we achieve immobilization of the unreacted monomer, which prevents any degradative processes from occurring at the counter electrode. This approach eliminated spot formation in the device and increased stability to over 10 000 cycles when compared to 500 cycles with conventional ProDOT devices wherein the monomer is not immobilized. The acrylated electrochromic polymer exhibits similar electrochromic properties as conventional ProDOT devices, such as photopic contrast (48% compared to 46%) and switch speed (both 2 s). This method can be applied to any one-layer electrochromic system where improved stability is desired.

We describe a new route for the synthesis of thieno[3,4-b]thiophene, alkyl derivatives thereof, seleno[3,4-b]thiophene, and thieno[3,4-b]furan made from inexpensive starting materials, such as thiophene-2-carboxylic acid and furan-2-carboxylic acid. Such fused heterocycles are of great interest for low band gap organic semiconductors and applications including OLEDs, organic photovoltaic cells, and electrochromics.

A series of dual polymer electrochromic devices (ECDs) based on 12 complementary pairs of conducting polymer films have been constructed using 3,4-ethylenedioxythiophene-containing conducting polymers. Poly[3,6-bis(2-(3,4-ethylenedioxythiophene))-N-methylcarbazole] (PBEDOT-NCH3Cz), poly[3,6-bis(2-(3,4-ethylenedioxythiophene))-N-eicosylcarbazole] (PBEDOT-NC20H41Cz), and poly[4,4‘-bis(2-(3,4-ethylenedioxythiophene))biphenyl] (PBEDOT-BP) were utilized as anodically coloring polymers that electrochemically switch between an oxidized deep blue absorptive state and a transmissive (orange or yellow) reduced state. Poly(3,4-ethylenedioxythiophene) (PEDOT) and its alkyl derivatives (PEDOT-C14H29 and PEDOT-C16H33) have been used as high-contrast cathodically coloring polymers that switch between a deep blue absorptive state in the reduced form and a sky blue, highly transmissive state in the oxidized form. The dual polymer ECDs were constructed by separating complementary pairs of EC polymer films, deposited on ITO...

We report the synthesis and electrochemical polymerization of a series of bisheterocycle-N-substituted carbazoles. These monomers exhibit low peak oxidation potentials (Ep,m) which range from 0.15 to 0.46 V vs Ag/Ag+, indicating facile polymerization. Repeated scan electrochemical polymerization for these monomers proceeds rapidly, relative to carbazole, to form stable electroactive films. Cyclic voltammetry of the polymers indicates that the films are well adhered to the electrode surface and that each of the polymers possess two distinct redox waves. At applied potentials greater than 1.15 V, a third irreversible oxidative process is observed, presumedly due to cross-linking. Optoelectrochemical analysis indicates that these polymers have an electronic bandgap (measured as the onset of the π-to-π* transition) between 2.4 and 2.5 eV. Three distinct colors are achievable by varying the redox state of the polymers suggesting potential use for multiply colored electrochromic displays. For the series of bis(...

We have carried out studies on an extensive series of electron rich monomers which oxidatively polymerize at low potentials. Alkyl derivatized poly(3,4-ethylenedioxythiophenes) (PEDOT's) exhibit a high degree of visible light transparency in the oxidized state, while being an opaque blue in the reduced state. These polymers can be switched rapidly (sub-second) between states with high optical contrasts of up to 60% AT. Multi-ring monomers have been prepared using EDOT moieties as terminal polymerizable un'rts, to yield the most easily oxidized thiophene based monomers reported to date, which efficiently electropolymerize. Polymers have been prepared with electronic band gaps that range from a relatively low 1.4 eV up to 2.5 eV. The inclusion of transition metal ions, electronically coupled to the conjugated backbone, allows further tuning of the polymer's redox properties. These polymers behave as complementary electrochromic materials and have been employed in dual polymer electrochromic devices. Judicious choice of proper cathodically and anodically coloring polymers yield devices which exhibit high optical contrasts (>50% T), multi-color capabilities, long term switching stability (>10 4 deep switches), and rapid switching characteristics with 25% optical contrast observed with 100 mS switches.

Diffusion of two monomers and their oxidative copolymerization inside a solid-state gel electrolyte is utilized as a method to match the monomer feed ratio to a color resulting from a conjugated copolymer having a single absorption in the visible region. Here, a combination of two monomers is used to generate a solid-state electrochromic device of any color, except black and green, in the colored state with all other colors going to transmissive sky blue in the bleached state.

A series of bis(2-(3,4-ethylenedioxy)thiophene)-based monomers have been synthesized and fully characterized; specifically (E)-1,2-bis(2-(3,4-ethylenedioxy)thienyl)vinylene (BEDOT-V), 1,4-bis(2-(3,4-ethylenedioxy)thienyl)benzene (BEDOT-B), 4,4‘-bis(2-(3,4-ethylenedioxy)thienyl)biphenyl (BEDOT-BP), 2,5-bis(2-(3,4-ethylenedioxy)thienyl)furan (BEDOT-F), 2,5-bis(2-(3,4-ethylenedioxy)thienyl)-thiophene (BEDOT-T), and 2,2‘:5‘,2‘‘-ter(3,4-ethylenedioxy)thiophene, TER-EDOT. The X-ray crystal structures of BEDOT-V and BEDOT-B have been determined. These monomers oxidize and polymerize at low potentials relative to other reported electropolymerizable heterocycles. The electroactive polymers formed exhibit low redox switching potentials and are quite stable in the conducting state. TER-EDOT was found to have the lowest peak oxidation potential of +0.2 V vs Ag/Ag+, making it the most easily oxidized polymerizable thiophene monomer reported. The electronic bandgaps of these EDOT based polymers range from 1.4 to 2.3 eV...

Poly(3,4-propylenedioxythiophene)s as a Single Platform for Full Color Realization Tanmoy Dey, Michael A. Invernale, Yujie Ding, Zeki Buyukmumcu, and Gregory A. Sotzing* The Polymer Program, Institute of Materials Science, Department of Chemistry, University of Connecticut, Storrs, Connecticut 06269, United States Department of Chemistry, Faculty of Science, Erciyes University, Kayseri 38039, Turkey

Processability remains a fundamental issue for the implementation of conducting polymer technology. A simple synthetic route towards processable precursors to conducting polymers (main chain and side chain) was developed using commercially available materials. These soluble precursor systems were converted to conjugated polymers electrochemically in aqueous media, offering a cheaper and greener method of processing. Oxidative conversion in aqueous and organic media each produced equivalent electrochromics. The precursor method enhances the yield of the electrochromic polymer obtained over that of electrodeposition, and it relies on a less corruptible electrolyte bath. However, electrochemical conversion of the precursor polymers often relies on organic salts and solvents. The ability to achieve oxidative conversion in brine offers a less costly and a more environmentally friendly processing step. It is also beneficial for biological applications. The electrochromics obtained herein were evaluated for electronic, spectral, and morphological properties.

Solid-state electrochromic windows from 3,4-propylenedioxythiophene (ProDOT) derivatives using dual polymer electrochromic architecture were fabricated and their electro-optical characteristics were recorded. DibenzylProDOT (DiBz-ProDOT) and biphenylmethyloxymethyl ProDOT (BPMOM-ProDOT) were used as cathodically coloring polymers, whereas bis(2-(3,4-ethylenedioxy)thienyl)-N-methyl carbazole (BEDOT-NMCz) was used as their complementary anodically coloring polymer. Straightforward assembly of the devices was designed by means of using a UV photo-curable gel. These devices exhibited response speeds of approximately 1 s with photopic contrasts as high as 52% for the complete device, and were found to exhibit good stability under open circuit conditions. Convenience of reporting photopic values to characterize electrochromic devices compared to reporting contrasts at a single wavelength is remarked., © Elsevier

Herein we report the patterning of large conducting polymer nanofiber mats of the polyterthiophene precursor, into regular micron scale arrays of smaller mats each of which has the potential of being independently addressed. These fiber grids, micro mats of conducting polymer fibers, were prepared by the combined techniques of electrospinning, soft photolithography, and solid state electrochemical crosslinking. The micro size mats are shown to retain their electrochromic behavior, subject to expected degradation in air as reported in the literature. Our contribution to the investigation of conducting polymers in display technology is oriented towards processibility and preparation of regular conducting polymer structures.

Here we report the synthesis of several new low oxidation monomers with the external rings being 3,4-ethylenedioxythiophene (EDOT). These monomers were prepared via NiCI2(dppp) catalyzed Grignard coupling in good yields and were found to exhibit low oxidation potentials with the lowest having an onset of 0.14 V for 2,2′:5′,2″-ter(3,4-ethylenedioxythienyl)thiophene (TER-EDOT). The polymers were found to be stable electrical conductors and were found to exhibit band gaps ranging from 1.4 eV for trans-1,2-bis(2-(3,4-ethylenedioxy)thienyl)vinylene (BEDOT-V) to 2.5 eV for the series of 3,6-bis(2-(3,4-ethylenedioxy)-thienyl)N-substituted carbazoles (BEDOT-NCz). BEDOT-V was found to be opaque purple in the reduced state and transmissive sky blue in the oxidized state while the BEDOT-NCz's are transmissive yellow in the reduced state, green upon mild oxidation and deep opaque blue in the oxidized state. Both the BEDOT-V and BEDOT-NCz's were found to exhibit fast response times and high contrast ratios upon redox stepping, thereby proving them useful for electrochromic coatings.

Complementary coloring conducting polymer based electrochromic devices have been designed, fabricated and tested for possible application as a variable attenuation combiner element for a see-through head mounted display or a variable trasnsmissive sand wind dust goggle lens. Electrochromic cells fabricated on both glass and polycarbonate substrates have been demonstrated to meet closely the desired goals of low power consumption, wide transmission range, fast switching speeds and long lifetime. Photopic transmissions of 34% in colored state and 67% in bleached state were achieved in a reproducible manner. The measured switching times are 0.6 sec (colored to bleached state) and 1.9 sec (bleached to colored state). The life cycle testing showed stability up to 92,000 switches. The measured power consumption of the fabricated devices was < 1 mW/cm . The electrochromic technology design effort has identified processes for obtaining the optimum layer thickness and selecting polymers and gel electrolytes necessary to obtain the widest transmission range, fastest switching speed and longest lifetime. Early environmental testing has been performed by subjecting prototype electrochromic cells to temperatures varying from -30°C to + 40°C with the results reported herein. Follow on work includes further optimization of electronic drive schemes as well as field testing of electrochromic lens equipped sand, wind dust goggles.

We demonstrate a facile controlling of the optical and colorimetric properties of a donor-acceptor conjugated polymer simply by varying the mix ratio of two precursors in a precursor blend. The conversion of a precursor blend results in an entirely new donor-acceptor polymer, distinct from the conjugated polymer of each precursor. Careful optimization of the mix ratio of two precursors results in a black electrochromic polymer.

A family of electrically conductive polymers based on 3,4-ethylenedioxythiophene (EDOT) and its derivatives will be discussed as electrochromic and redox electroactive materials. Poly(alkylethylenedioxythiophenes), derivatized with octyl and tetradecyl pendant chains, exhibit significantly faster redox switching characteristics than the unsubstituted parent polymer. Bis(2-(3,4-ethylenedioxy)thienyl)arylene (BEDOT-Ar) and vinylene monomers electropolymerize at low potentials avoiding degradative side reactions. We outline the properties of EDOT polymers which exhibit low band gaps allowing for the formation of conductive complexes with a high degree of visible light transmission and show their electrochromic properties. The BEDOT-vinylene polymer, for example, has a band gap of 1.4 eV. A relatively high degree of electrochromic contrast is found at 600 nm as the polymers switch between insulating deep purple absorptive and conductive light blue states. Solid-state dual polymer electrochromic devices have been constructed using a combination of complementary anodically and cathodically coloring polymers based on the EDOT core.

The dual polymer configuration is commonly used when constructing electrochromic devices (ECDs) due to the expected electrochemical stability and enhanced optical properties. In this configuration, two different polymers are used which are optically complementary. Herein we report the construction and characterization of dual-type ECDs using poly(3, 4-ethylenedioxythiophene) (PEDOT) and poly[3, 6-bis(2-(3, 4-ethylenedioxy)thienyl)-N-methylcarbazole] (PBEDOT-NMCz) as the two complementary electrochromic polymers for the device. A variety of gel electrolyte solutions were prepared and evaluated for these devices. The use of ionic liquids within these gels imparted interesting properties, including long lifetimes, and thermal stability of devices. Switching speeds for the various devices, as well as optical contrasts, were also obtained for the gel electrolytes containing different amounts of ionic liquid as plasticizer.