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.     

Preparation of electrochromic Ni1−xO and TiO2 coatings from pigment dispersions and their application in electrochromic foil based devices

Thin (100–400 nm) electrochromic TiO₂ and Ni_1−xO coatings providing transmissive light modulation were made from an anatase pigment dispersion obtained by co-grinding nanocrystalline titanium particles (6–10 nm in size) with trisilanol heptaisobutylsilsesquioxane as dispersant, while Ni_1−xO based pigment dispersions were made by milling pre-prepared Ni_1−xO pigment with nickel oxyhydroxide (NiO_xH_y) dispersant. Dispersions were obtained by milling the pigments with zirconia beads of various sizes (0.1, 0.2 and 0.4 mm) and the particle size was determined with the dynamic light scattering technique (DLS). Pigment dispersions were deposited by spin-coating on glass and plastic (PET) film and thermally treated at 150 °C to obtain thin TiO₂ and Ni_1−xO pigment coatings. SEM and AFM were used for determination of the surface morphology, revealing their homogenous structure and low surface roughness (up to 20 nm). The optical transmittance and haze of the coatings deposited on glass and PET film were determined from the UV–vis spectra. Their electrochromic effect was analyzed by electrochemical charging/discharging the coatings in a LiClO₄/PC electrolyte. The results demonstrated a convenient, simple and robust technique for making “electrochromic paint” coatings. Pre-prepared TiO₂ and pigments were used for construction of foil-based electrochromic devices with transmissive modulation of light.     

Effect of the thicknesses of the Al2SiO5 ion conductor on the opto-electrical properties for all-solid electrochromic devices

In this study, an all-solid-state electrochromic device (ECD) with the structure of ITO/WO₃/Al₂SiO₅/NiO_x/ITO was prepared, and the effect of the Al₂SiO₅ solid electrolyte thicknesses on the opto-electrical performance was investigated. The microstructure and surface morphology were characterized using XRD, SEM and AFM, and the surface morphology and degree of surface looseness demonstrate a significant influence on the opto-electrical properties of ECDs. The charge transfer dynamics at the solid-solid interface were characterized using EIS to obtain an ionic conductivity of 4.637 × 10^-8 S/cm. CV, CA and UV–Visible spectra were employed to record the in situ electrochemical and optical properties. The results revealed that the highest optical modulation was 44.58%, the coloring and bleaching times were 14.8 s and 3.7 s, and the highest coloring efficiency was 98.17 cm²/C, which indicates that excellent opto-electrical properties were obtained. When the thickness increases, the degree of surface dense morphology transforms, and the loose morphology is more favorable for ion conductivity, which improves the opto-electrical properties. The results in this study provide insights into the understanding of Al³⁺-based all-solid-state ECDs, which promote the exploration of new types of Al³⁺ ionic conductors for all-solid-state ECDs.     

Solid-state electrochromic devices with Nb2O5:Mo thin film and gelatin-based electrolyte

A gelatin-based electrolyte has been developed and characterized by impedance spectroscopy, X-ray diffraction, UV-vis-NIR spectroscopy and atomic force microscopy (AFM). The heat treatment temperature was found the key factor affecting its ionic conductivity that increases from 1.5 × 10⁻⁵ S/cm to 4.9 × 10⁻⁴ S/cm by heating from room temperature up to 80 °C. The temperature dependence of the ionic conductivity exhibits an Arrhenius behavior. EC-devices with the configuration K-glass/Nb₂O₅:Mo EC-layer/gelatin-based electrolyte/(CeO₂)_x(TiO₂)_1−x ion-storage (IS) layer/K-glass, have been assembled and characterized. They show a good long time cyclic stability, but the change of the optical density measured at 550 nm after 25 000 cycles was only 0.13.     

Fabrication of electrochromic devices by laser patterning of spin-sprayed transparent conductive Ga:ZnO films

Despite their significant economic benefits, wet processes are rarely adopted in optoelectronics industries because of their inherent difficulties in producing high-quality functional films compared with dry processes. Unlike other conventional wet processes, spin-spraying promotes surficial heteronucleation by continuously providing fresh source ions onto the substrate surface and removing excess ions left after nucleation from the surface. Surficial heteronucleation ensures the formation of high-quality films with dense microstructures that are comparable to those obtained by dry processes. This study describes a novel spin-spraying method for growing Ga-doped ZnO (Ga:ZnO) films on glass substrates. The optimum Ga doping concentration of the spin-sprayed Ga:ZnO (SSedGZO) films was determined from the electrical and optical properties of the films. Further, the feasibility of employing UV laser patterning to produce patterned SSedGZO films for application as transparent electrodes (TEs) in optoelectronic devices was evaluated, and the optimum laser power required for effective patterning was determined by analyzing the surface microstructures of the patterned films. Finally, to confirm the practical applicability of the SSedGZO films as TEs, electrochromic devices (ECDs) comprising the SSedGZO TEs were fabricated. The laser-patterned SSedGZO TEs functioned successfully in the fabricated ECDs, displaying reversible color changes through electrochromic switching.     

PB/ITO-PET柔性电致变色薄膜制备及性能研究

柔性电致变色器件具有体积小、重量轻、可弯曲等优点,在可穿戴设备、曲面显示器、节能及自适应伪装等领域具有潜在应用前景。本工作以铁氰化钾、氯化钾、无水氯化铁为原料,采用电沉积方法在ITO-PET柔性基底上沉积普鲁士蓝(PB)制得PB/ITO-PET电致变色薄膜,并利用扫描电子显微镜、紫外光谱仪、电化学工作站对PB/ITO-PET电致变色薄膜微观结构和电化学性能进行分析表征。结果表明,电沉积时间为200 s时得到的PB/ITO-PET电致变色薄膜在700 nm波长处光吸收率达到0.755,且PB/ITO-PET电致变色薄膜可在较低电压(0.6 V/-0.3 V)下实现着色和褪色。其光调制范围为68%,着色/褪色响应时间分别为9 s/8 s,着色效率为108 cm2/C。PB/ITO-PET电致变色薄膜经1000次着色-褪色循环后光调制范围为68%,着色效率为100.3 cm2/C。PB/ITO-PET电致变色薄膜500次弯曲,着色效率为105.5 cm2/C,并经1000次着色-褪色循环后着色效率为91 cm2/C,光调制范围为65%。利用ITO-PET为离子存储层(对电极)、凝胶电解质和PB/ITO-PET为工作电极组装得到柔性电致变色器件,其光调制范围为53%,着色/褪色响应时间分别为13 s/18 s。     

Electrosynthesis and characterization of an electrochromic material from poly(1,4-bis(2-thienyl)-benzene) and its application in electrochromic devices

1,4-Bis(2-thienyl)-benzene monomer is successfully synthesized via coupling reaction. Poly(1,4-bis(2-thienyl)-benzene) (PBTB) is electrochemically synthesized and characterized. Resulting polymer film has distinct electrochromic properties. Its application in electrochromic devices (ECDs) is discussed. PBTB is switched between yellow in the neutral state and green in the oxidized state. Electrochromic switching of PBTB film is performed and the polymer film shows a maximum optical contrast (ΔT %) of 44.8% at 610 nm in visible region with a response time of 1.6 s. The coloration efficiency (CE) of PBTB is calculated to be 162 cm² C⁻¹. Electrochromic device (ECD) based on PBTB and poly(3,4-ethylenedioxythiophene) (PEDOT) is also constructed and characterized. Maximum contrast (ΔT %) and switching time of the device are measured as 29.5% and 0.43 s at 628 nm. The CE of the device is calculated to be 408.9 cm² C⁻¹. Clear change from green (at neutral state) to blue color (at full oxidized state) of this ECD is demonstrated with reasonable cycle life.     

Composition effects on ion transport in a polyelectrolyte gel with the addition of ion dissociators

The polymerization of lithium 2-acrylamido-2-methyl-1-propane sulphonic acid with N,N′-dimethylacrylamide has yielded polyelectrolyte gels which have the favourable property of being single ion conductors. The use of single ion conductors ensures that the transport number of lithium is close to unity. The mobility of the lithium ion is still quite low in these systems, resulting in low ionic conductivity. To increase ionic conductivity more charge carriers can be added however competing effects arise between increasing the number of charge carriers and decreasing the mobility of these charge carriers. In this paper the monomer ratio of the copolymer polyelectrolyte is varied to investigate the effect increasing the number of charge carriers has on the ionic conductivity and lithium ion and solvent diffusivity using pfg-NMR. Ion dissociators such as TiO₂ nano-particles and a zwitterionic compound based on 1-butylimidazolium-3-(N-butanesulfonate) have been added in an attempt to further increase the ionic conductivity of the system. It was found that the system with the highest ionic conductivity had the lowest solvent mobility in the presence of zwitterion. Without zwitterion the mobility of the solvent appears to determine the maximum ionic conductivity achievable.     

Synthesis of transfer-free graphene films on dielectric substrates with controllable thickness via an in-situ co-deposition method for electrochromic devices

The solutions and polymer supported materials in graphene transfer process would introduce lots of containments, defects and wrinkles, which weakens the performance of graphene. Herein, an in-situ co-deposition method is carried out to obtain transfer-free graphene films with controllable thickness on several dielectric substrates. The amorphous carbon (carbon source) and copper (catalyst) are co-deposited on dielectric substrates. Followed by an in-situ annealing process, the amorphous carbon is transformed to few-layer graphene. High co-deposition temperature could promote the decomposition of Cu(acac)₂ precursors, leading to the controllable thickness of amorphous carbon layer in Cu@C films. Finally, 3-, 5-, 8- and 10- layers graphene films with transmittance of up to 93.5% and square resistance of 0.8 kΩ·sq^?1 are obtained and a high-performance electrochromic device is fabricated using 3 layers graphene films as electrodes. The “color” and “bleach” time of the electrochromic device is 16.6 s and 6.8 s with the transmittance of 26.8% and 79.7% separately. This method paves an alternative way for the batch production of transfer-free graphene film as electrode materials.     

Preparation and characterization of nanocomposite polyelectrolyte membranes based on Nafion ionomer and nanocrystalline hydroxyapatite

In this study nanocrystalline hydroxyapatite (nHA) was synthesized and characterized by means of FT-IR, XRD and TEM techniques and a series of proton exchange membranes based on Nafion^® and nHA were fabricated via solvent casting method. Thermogravimetric analysis confirmed thermal stability enhancement of the Nafion^® nanocomposite due to the presence of nHA nanopowder. SAXS and TEM analyses confirmed the incorporation of nHA into ionic phase of Nafion^®. Furthermore, the incorporation of elliptical nHA into the Nafion^® matrix improved proton conductivity of the resultant polyelectrolyte membrane up to 0.173 S cm⁻¹ at 2.0 wt% of nHA loading compared to that of 0.086 S cm⁻¹ for Nafion^® 117. Also, the inclusion of nHA nanoparticles into nanocomposite membranes resulted in a significant reduction of methanol permeability and crossover in comparison with pristine Nafion^® membranes. Membrane selectivity parameter of the nanocomposites at 2.0 wt% nHA was calculated and found to be 106,800 S s cm⁻³, which is more than two times than that of Nafion^® 117. Direct methanol fuel cell tests revealed that Nafion^®/nHA nanocomposite membranes were able to provide higher fuel cell efficiency and also better electrochemical performance in both low and high concentrations of methanol feed. Thus, the current study shows that nHA enhances the functionality of Nafion^® as fuel cell membranes.     

A processable rainbow mimic fluorescent polymer and its unprecedented coloration efficiency in electrochromic device

A processable rainbow mimic fluorescent polymer (PSNSF) based on 1-(9H-fluoren-2-yl)-2,5-di(thiophen-2-yl)-1H-pyrrole (SNSF) was synthesized via electrochemical polymerization in a mixture of ethanol and CH₂Cl₂ solution containing 0.1 M LiClO₄. Characterization was carried out using cyclic voltammetry, UV-vis and FT-IR spectroscopic techniques. Also, an electrochromic device based on PSNSF was studied, which exhibits high coloration efficiency (CE), high redox stability (retaining 98.6% of its optical activity after 4000th switch) and very low response time (less than 0.5 s).     

Colorimetric chemosensor for Ni2+ based on alizarin complexone and a cationic polyelectrolyte in aqueous solution

A new and convenient chemosensor for detecting Ni²⁺ in aqueous buffer has been developed by mixing an anionic organic dye, alizarin complexone (ALC) and a cationic polyelectrolyte, poly(diallyldimethylammonium chloride) (PDADMAC). After addition of Ni²⁺, the chemosensor exhibits a remarkable bathochromic shift with a significant color change from red to blue, while other metal ions did not induce such a change. The color change may be attributed to the aggregate formation of an ALC-based Ni²⁺ complex on the surface of PDADMAC. The results showed that the ALC and PDADMAC mixture can be applied to detect Ni²⁺ selectively with colorimetric changes. This investigation can lead to the construction of new chemosensors by facile and simple mixture of a water-soluble dye and an oppositely charged polyelectrolyte. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47496.     

Colorimetric detection of Hg2+ using a mixture of an anionic azo dye and a cationic polyelectrolyte in aqueous solution

We investigated a colorimetric chemosensor for Hg²⁺ based on a mixture of xylidyl blue I as an anionic organic dye and poly(diallyldimethylammonium chloride) as a cationic polyelectrolyte in an aqueous solution at pH 7.5. The addition of Hg²⁺ to the mixture induced a bathochromic shift in the absorption spectra with a distinct color change from red to green which was readily identifiable by the naked eye, whereas the other metal ions gave rise to insignificant color changes. By contrast, upon adding Hg²⁺ to xylidyl blue I alone, the solution underwent no significant change in color. Moreover, a stoichiometric ratio for the complex between xylidyl blue I and Hg²⁺ in the presence of poly(diallyldimethylammonium chloride) was determined to be 1:1 by the absorption titration curve and Job's plot. Thus, the mixture can be used as a selective naked‐eye colorimetric chemosensor for Hg²⁺ over other common metal ions. This study raises the possibility that the combination of an organic dye and an oppositely charged polyelectrolyte is a potential candidate for the easy construction of a new chemosensor system. © 2018 Society of Chemical Industry     

High contrast asymmetric solid state electrochromic devices based on layer-by-layer deposition of polyaniline and poly(aniline sulfonic acid)

Layer-by-layer (LbL) self-assembly was employed for alternating deposition of two electrochromic polymers to fabricate a single film composite. We report a wide spectral range, high contrast asymmetric solid state electrochromic device, fabricated by LbL assembly of the polycation polyaniline (emeraldine base) (PANI) and the polyanion poly(aniline sulfonic acid), (PASA). Detailed spectral and electrochemical investigation of the dual electrochrome thin film confirm that both electrochromic polymers contribute to the electrochromic and electrochemical characteristics of the composite. Under the application of ±2.3 V potential the system exhibited an average contrast of 49.7% across the full visible spectrum. The dual electrochrome system was compared to single electrochrome systems, and it was observed that PANI predominantly affects the electrochromic optical spectra of the composite, whereas PASA increases the switching speed.     

Design and fabrication of MoSe2/WO3 thin films for the construction of electrochromic devices on indium tin oxide based glass and flexible substrates

Electrochromic devices (ECDs) have the ability to block the heat generated by sunlight, making them ideal for use in smart windows. Herein, we report the fabrication of ECDs using MoSe₂/WO₃ (MSW) as the electrochromic material, for smart windows applications. A solvothermal method was used for the synthesis of MoSe₂, while WO₃ was synthesized using a sol-gel approach. Subsequently, MoSe₂/WO₃ (MSW) hybrids with different wt% of MoSe₂ (0.05 wt%, 0.2 wt%, 0.5 wt%) were synthesized using an ultra-sonication approach. The physicochemical features of these MSW hybrids herein termed as MSW 0.05, MSW 0.2 and MSW 0.5, were investigated using X-ray diffraction (XRD), X-ray photon electron spectroscopic (XPS), scanning electron microscope (SEM), and EDS techniques and compared with pristine MoSe₂ and WO₃. The ECDs synthesized using MSW 0.05 showed increased coloration efficiency (62 cm^2 C-1) with an applied potential range of 0 to −1.5 V. Subsequently, the ECDs based on indium tin oxide (ITO) and MSW 0.05 demonstrated excellent electrochromic performance and stability for 10,000 cycles. The enhanced electrochromic performance of the MSW-based ECDs may be attributed to the conductive nature as well as the synergistic effects between MoSe₂ and WO₃ when compared to the WO₃-based ECDs. The synthesized MSW also showed promise as an electrochromic material in flexible ECDs for smart windows applications.     

Preparation and characterization of hybrid nanocomposite coatings by photopolymerization and sol-gel process

Organic-inorganic nanocomposite hybrid coatings were prepared through a dual-cure process involving cationic photopolymerization of epoxy groups and subsequent condensation of alkoxysilane groups. The kinetics of the photopolymerization and condensation reactions were investigated; suitable conditions for obtaining a complete conversion of both reactive groups were found. The obtained films are transparent to visible light. The T_g values of the hybrids increase by increasing the TEOS content in the photocurable formulation. Also, a significant increase in surface hardness could be obtained for the hybrid systems. AFM analysis gave evidence of a strong interaction between the organic and inorganic phase with the formation of silica domains in the nanoscale range.     

Sedimentation behaviour in dilute solutions of a polyelectrolyte

Sedimentation velocity studies are reported for dilute aqueous solutions of sodium poly(styrene sulphonate) with various quantities of added NaCl. On increasing the salt concentration the dependence of 1/S on polymer concentration decreases and, up to 0.5 M NaCl, the limiting sedimentation coefficient increases. These changes are related to changes in the effective charge on the polymer, which increases with increasing salt concentration, and in the friction coefficient, which decreases with increasing salt concentration. The effective charge on the polymer should be considered when evaluating the Mandelkern-Flory parameter, $\text{ø}{}^{\mathrm{<mtext>1</mtext><mtext>3</mtext>}}\text{P}{}^{\mathrm{?1}}$.     

Study and optimization of a flexible electrochromic device based on polyaniline

The synthesis of polyaniline (PANI) thin films was made onto commercially available  cm polyethylene terephthalate (PET)/indium tin oxide (ITO) substrates. By depositing a gold frame previously to the electrochemical PANI synthesis, homogeneous electrochromic PANI layers were obtained. Complete flexible cells could then be built by using a transparent gel electrolyte and a simple PET/ITO counter-electrode. Branched poly(ethyleneimine) (BPEI)-H₃PO₄ and polymethylemethacrylate (PMMA)-PC-LiClO₄ were both tested as electrolytes, but only the latter led to a non-degrading system when the device undergoes several switching potential steps. This flexible, middle-scale and inexpensive device enabled to get a 18% transmission contrast at 780 nm within 3 min.     

Effects of solution pH on ion distribution and drug release behaviors of a weak polyelectrolyte hydrogel

A triphasic model is developed and the finite element method is adopted to investigate a weak polyelectrolyte hydrogel. The influence of HCl concentrations in external solution on ion concentrations inside the hydrogel and the evolution of water volume fraction are discussed. The conservation of charge can be satisfied everywhere in the hydrogel. Also, a drug release equation which considers both convection and diffusion effects is employed to analyze the drug release rate. The results show that the drug release rate has a very close relationship with the pH value. The simulated results are compared with experimental results of Beebe to validate the reliability and accuracy of this simulation. This work is significant for the study of oral drug controlled release in the gastrointestinal tract. © 2017 Society of Chemical Industry