Highly Tunable Nanostructures in a Doubly pH-Responsive Pentablock Terpolymer in Solution and in Thin Films

Multiblock copolymers with charged blocks are complex systems that show great potential for enhancing the structural control of block copolymers. A pentablock terpolymer PMMA-b-PDMAEMA-b-P2VP-b-PDMAEMA-b-PMMA is investigated. It contains two types of midblocks, which are weak cationic polyelectrolytes, namely poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) and poly(2-vinylpyridine) (P2VP). Furthermore, these are end-capped with short hydrophobic poly(methyl methacrylate) (PMMA) blocks in dilute aqueous solution and thin films. The self-assembly behavior depends on the degrees of ionization α of the P2VP and PDMAEMA blocks, which are altered in a wide range by varying the pH value. High degrees of ionization of both blocks prevent structure formation, whereas microphase-separated nanostructures form for a partially charged and uncharged state. While in solutions, the nanostructure formation is governed by the dependence of the P2VP block solubility of the and the flexibility of the PDMAEMA blocks on α, in thin films, the dependence of the segregation strength on α is key. Furthermore, the solution state plays a crucial role in the film formation during spin-coating. Overall, both the mixing behavior of the 3 types of blocks and the block sequence, governing the bridging behavior, result in strong variations of the nanostructures and their repeat distances.     

全固态聚苯胺-二氧化钛电致变色器件的制备

以聚苯胺(PANI)为电致变色材料,分别制备了对称结构(SSECD,ITO‖PANI‖解质‖PANI‖lTO)和非对称结构(ASECD,ITO‖PANI‖电解质‖TiO<,2>‖ITO)的全固态电致变色器件.TO<,2>薄膜的制备采用提拉法.经500℃处理后得到锐钛矿结构,所得薄膜由粒径10-20 nm的TiO<,2>...     

A Solution‐Processable High‐Coloration‐Efficiency Low‐Switching‐Voltage Electrochromic Polymer Based on Polycyclopentadithiophene

A solution‐processable electrochromic (EC) polymer, poly(4,4‐dioctyl‐cyclopenta[2,1‐b:3,4‐b′]‐dithiophene) (PDOCPDT) is prepared by means of chemical oxidative polymerization of the corresponding monomer. The UV‐vis spectrum of the spin‐coated PDOCPDT film displays an absorption maximum of 580 nm. Although the polymer is deep blue in its neutral state, it turns to transparent bluish after being oxidized. PDOCPDT film (thickness 120 nm) exhibits high coloration efficiency (CE)—as high as 932 C cm^–2 at 580 nm, low response time (0.75 s), high optical density (0.75 at 580 nm), and high‐level stability for long term switch (it switches repetitively 1000 times with less than 8 % contrast loss). The electrochemical stability and redox potentials of PDOCPDT films are independent of film thickness (50–180 nm) and active area (up to 2 cm × 2 cm). Nevertheless, optical contrast increases as the film thickness increases, although the CE and response time changes irregularly with the film thickness. The good EC properties combined with the easy film fabrication process make PDOCPDT a notable candidate for application in EC devices. (ECDs) A simple transmissive‐type ECD with good CE using PDOCPDT film as an active layer is also demonstrated.     

Hybrid electrochromic film based on polyaniline and TiO2 nanorods array

Titanium dioxide (TiO₂) nanorods (NRs) array was successfully prepared via hydrothermal method on fluorine doped tinoxide (FTO) coated transparent conductive glass substrate. The hybrid film of polyaniline (PANI)/TiO₂ NRs was achieved through electrochemical polymerization of aniline onto the TiO₂ NRs array film. The electrochromic and optical properties of the hybrid film were investigated by cyclic voltammetry (CV), amperometric i–t and UV–vis spectroscopy. The results indicate that the hybrid film has long term stability and reversible color changes after cyclic voltammetry scans for 200 circles. The PANI/TiO₂ NRs hybrid film can show three different colors. Response time of PANI/TiO₂ NRs hybrid film is about 0.7 s and 2.6 s at different states, respectively. The TiO₂ NRs array and the loose, porous surface among the hybrid film facilitate charge transmission and also provide large surface area for electrochemical reaction.     

A new electrochromic copolymer based on dithienylpyrrole and EDOT

A new compound, namely diethyl 2,5-di(thiophen-2-yl)-1H-pyrrole-3,4-dicarboxylate (1), was copolymerized with 3,4-ethylenedioxythiophene (EDOT) via electrochemical method. The copolymer exhibits multicolor electrochromic property: It is found that the copolymer, poly(1-co-EDOT), has a specific optical band gap (1.71 eV) to reflect and/or transmit reddish brown color in the neutral state, and it can be switched to reddish orange, orange, yellowish green and blue colors upon oxidation in a low switching time (1.0 s). Importantly, these colors are essential for camouflage and/or full color electrochromic device/display applications. In addition to these, the obtained copolymer has a coloration efficiency of 173 cm²/C at 500 nm.     

Effects of surface porosity on tungsten trioxide(WO3) films’ electrochromic performance

In this paper, the correlation between the electrochromic performance and the surface morphology of the tungsten trioxide (WO₃) thin films sputtered by dc reactive magnetron sputtering with widely varying target-substrate distances was investigated. It is found that the optical density change (ΔOD) of films is strongly affected by the target-substrate distance. The coloration efficiency (CE) at 633 nm was also found to be sensitive to the target-substrate distance, with 16 cm²/C of film sputtered at 6 cm and 50 cm²/C at 18 cm. X-ray diffraction showed that the crystal structure of films was amorphous. By using atomic force microscope to identify the surface porosity of the sputtered WO₃ films, we found that the film at longer target-substrate distance was rough, porous, and having a cone-shaped columns morphology, thus offering a good electrochromic performance for opto-switching applications.     

New Roll‐to‐Roll Processable PEDOT‐Based Polymer with Colorless Bleached State for Flexible Electrochromic Devices

Conjugated electrochromic (EC) polymers for flexible EC devices (ECDs) generally lack a fully colorless bleached state. A strategy to overcome this drawback is the implementation of a new sidechain‐modified poly(3,4‐ethylene dioxythiophene) derivative that can be deposited in thin‐film form in a customized high‐throughput and large‐area roll‐to‐roll polymerization process. The sidechain modification provides enhanced EC properties in terms of visible light transmittance change, Δτ_v = 59% (ΔL* = 54.1), contrast ratio (CR = 15.8), coloration efficiency (η = 530 cm² C^?1), and color neutrality (L* = 83.8, a* = ?4.3, b* = ?4.1) in the bleached state. The intense blue‐colored polymer thin films exhibit high cycle stability (10 000 cycles) and fast response times. The design, synthesis, and polymerization of the modified 3,4‐ethylene dioxythiophene derivative are discussed along with a detailed optical, electrochemical, and spectroelectrochemical characterization of the resulting EC thin films. Finally, a flexible see‐through ECD with a visible light transmittance change of Δτ_v = 47% (ΔL* = 51.9) and a neutral‐colored bleached state is developed.     

Bioinspired Controllable Electro‐Chemomechanical Coloration Films

Coloration materials and devices with broad manipulatable color spectra and precisely controllable capability are highly pursued in various applications, such as camouflage engineering, optical sensors, anticounterfeiting technology, real‐time monitoring, and so on. For achieving the goals, in the present work, a conceptually novel bioinspired coloration film is demonstrated using nanoscale amorphous silicon (a‐Si) layer deposited on a reflective metal substrate. With precisely manipulating the reversible lithiation/delithiation behaviors, such coloration films enable to present consecutively tunable chromogenic property in a broad visible band, since the simultaneous changes in both chemical components and film thickness upon electrochemical processes substantially vary the conditions of destructive interference. Accordingly, the corresponding model based on electro‐chemomechanical coupling effects confirms the coloration mechanism induced by thickness and intrinsic properties (refraction index and optical absorptivity). Additionally, such coloration films also suggest universal design ability, namely tailoring the coloration spectra via simply changing film thicknesses and metal substrates. Thus, the results promise a versatile strategy for fabricating advanced coloration materials and devices that are pursued in specular reflection, sensing, anticounterfeiting, labels, displaying, and sensors.     

Electrochemical Synthesis of Optically Active Polyaniline Films

Polyaniline (PANI) thin films with high optical activity are prepared electrochemically on indium tin oxide (ITO) substrates by polymerizing aniline in the presence of aniline oligomers and optically active camphor sulfonic acid (CSA). These optimized PANI chiral thin films have an anisotropic factor of 0.03 and an estimated molar ellipticity of 8.8 × 10⁵ deg cm² dmol^–1, ～ 25 % higher than our previously synthesized chiral PANI nanofibers that were prepared using the chemical method. The thin film prepared without aniline oligomers is basically achiral. The electrochemical method does not require an oxidizing agent and allows control of the rate of polymerization reaction by varying the oxidation potential. The electrochemical polymerization also ensures that the initiation occurs solely with the oligomers. Varying the experimental parameters, such as oxidation potential and the choice of oligomers, allows tuning of optical activity, adsorption properties, crystallinity, and morphology of the PANI thin films.     

Highly stable covalently-bonded organic-inorganic materials: Synthesis and electrochromic properties

Indium tin oxide (ITO) electrode was modified with anilino-methyl-triethoxysilane (AMTS), and then the polyaniline film covalently bonded to ITO electrode (PANI-ITO) was prepared by the chemical oxidation polymerization. The adhesive strength of PANI film on ITO electrode was tested by sonication. It was found that PANI-ITO exhibited a much better stability than that on bare one. Cyclic voltammetry (CV) and UV–vis spectroscopy measurements indicated that the oxidative potentials of PANI-ITO decreased and the film exhibited high electrochemical activities and lithium storage capacity. Moreover, the coloration time was 2.1 s, while the bleaching time was 1.0 s. It can be found that PANI-ITO exhibits the better electrochromic properties.     

Design of color tunable thin film polymer solar cells for photovoltaics printing

Color tunable thin film polymer solar cells have demonstrated the potentials of a wide applications in photovoltaics printing, which is significant for ink pollution reduction and energy saving. This work presents a new effective approach to realize color-tuning photovoltaic cells with optical microcavity structures. Aluminum-doped zinc oxide is utilized as electron transport layer material. With its high electrical conductivity, the thickness tuning range can be quite large, which means the cavity length has a wide variation range. It thus provides sufficient space for optical thin film design to obtain multi colors. By the transfer matrix method, device reflection and absorption spectra are numerically investigated. Based on that, the optical principles for color tunability are explored. In further step, the relationship between device photovoltaics performance and reflective colors are also discussed. Finally, the color coordinates and luminosities are calculated. As results, the colors of the devices designed are capable to cover a relatively large region in Commission Internationale de l′Eclairage(CIE) 1931 x, y chromaticity diagram, which is available to be integrated into the advertisement poster boards, building wall printing and other display applications.     

电致变色NiO_x薄膜及其研究现状

介绍了阳极电致变色氧化镍薄膜的研究现状，制备条件对薄膜形貌、晶粒结构和化学计量比的影响，以及微观结构与薄膜的动态致色范围、致色效率、响应时间的关系，分析了离子注入问题以及电致变色机理。     

Electrochromism and photoelectrochemical perfor- mance of WO3/Au composite film electrodes

WO₃/Au composite film electrode was prepared by hydrothermal combined electrodeposition method. The samples were characterized by scanning electron microscope(SEM), energy dispersive spectrometer(EDS) and X-ray diffraction(XRD), and the results showed that WO₃/Au composite film was synthesized. Electrochemical and spectral measurements were carried out to obtain the electrochromic response time, reversibility, coloration efficiency(CE) and transmittance of the WO₃     

Enhanced Electrochromism with Rapid Growth Layer‐by‐Layer Assembly of Polyelectrolyte Complexes

In this work, a facile method to deposit fast growing electrochromic multilayer films with enhanced electrochemical properties using layer‐by‐layer (LbL) self‐assembly of complex polyelectrolyte is demonstrated. Two linear polymers, poly(acrylic acid) (PAA) and polyethylenimine (PEI), are used to formulate stable complexes under specific pH to prepare polyaniline (PANI)/PAA‐PEI multilayer films via LbL deposition. By introducing polymeric complexes as building blocks, [PANI/PAA‐PEI]_n films grow much faster compared with [PANI/PAA]_n films, which are deposited under the same condition. Unlike the compact [PANI/PAA]_n films, [PANI/PAA‐PEI]_n films exhibit porous structure that is beneficial to the electrochemical process and leads to improved electrochromic properties. An enhanced optical modulation of 30% is achieved with [PANI/PAA‐PEI]₃₀ films at 630 nm compared with the lower optical modulation of 11% measured from [PANI/PAA]₃₀ films. The switching time of [PANI/PAA‐PEI]₃₀ films is only half of that of [PANI/PAA]₃₀ films, which indicates a faster redox process. Utilizing polyelectrolyte complexes as building blocks is a promising approach to prepare fast growing LbL films for high performance electrochemical device applications.     

Macro-/mesoporous Metal–Organic Frameworks Templated by Amphiphilic Block Copolymers Enable Enhanced Uptake of Large Molecules

The first synthesis of hierarchical porous metal–organic frameworks (HP-MOFs) is reported through a solvent evaporation-induced co-assembly of polystyrene-block-poly(ethylene oxide) (PS-b-PEO) and MOF building blocks. The growth of MOFs is restricted to confined spaces formed by self-assembled PS-b-PEO, and mesopores and/or macropores are created after removing PS-b-PEO by solvent rinsing. This approach avoids phase separation and competitive interactions between templates and MOF building blocks. Both amorphous and crystalline HP-MOFs can be synthesized by finely controlling MOF growth conditions. Additionally, HP-MOFs (ZIF-L sheets) with honeycomb-like channels show significantly enhanced incorporation of large guest molecules compared to microporous MOFs. This study establishes an efficient synthetic strategy for preparing HP-MOFs with highly accessible mesopores and macropores for applications involving large molecules.     

射频磁控溅射制备非晶WO3薄膜的结构及其光电性质研究

采用射频磁控溅射技术,以WO3陶瓷靶为原料,在透明导电氧化铟锡（ITO）玻璃上沉积了非晶相WO3薄膜,研究了溅射功率对薄膜结构及光学性质的影响,并研究了WO3薄膜的电致变色特性。利用扫描电子显微镜（SEM）、X射线衍射技术（XRD）表征了薄膜的表面形貌和内部结构;利用UV-Vis分光光度计表征了薄膜在变色前后的光学透过性质,利用电化学测试工作站研究了WO3薄膜的电致变色性质,并从原理上分析了WO3薄膜的变色机理。研究结果表明,不同功率下获得的WO3薄膜均为非晶结构,在可见光范围内有较高的透过率。透明的WO3薄膜在负向电压下逐渐转变成深蓝色,且在撤去电压后其颜色不变,当施加正向电压时,薄膜又转换为透明态,表现出良好的电致变色特性。所制备WO3薄膜在550nm处褪色态的透过率为83%,着色态的透过率为29%,使得该薄膜在智能窗方面具有广阔的应用前景。     

Preparation of Surfactants Directed PANI/In2O3 Nanocomposite Thin Films and Its NH3-Sensing Properties

Polyaniline/indium oxide (PANI/In2O3) nanocomposite thin films have been prepared in water-dispersed medium with the presence of different surfactants by an in-situ self-assembly technique. A cationic surfactant TTAB (tetradecyltrimethylammonium bromide) and a non-ionic surfactant tween- 20 (poly (ethylene oxide) (20) sorbitan monolaurate) are used as additives. The nanocomposites and thin films are characterized by Fourier transform infrared (FTIR), transmission electron microscopy (TEM), and scanning electron microscopy (SEM), respectively. The optical properties reveal the interaction between PANI/In2O3 nanocomposites and surfactants, and PANI/In2O3 thin films prepared in the presence of surfactants exhibits the finer nanofiber than the surfactants free PANI/In2O3 thin film. The ammonia (NH3) gas-sensing characteristic of PANI/In2O3 thin films and the effect of different surfactants on the gas-sensing property are studied. The results indicated that the film processed in the presence of TTAB has the highest gas sensitivity among all the prepared films.     

Effect of electrode surface on the electrochromic properties of electropolymerized poly(3,4-ethylenedioxythiophene) thin films

Electrochromism or electrochromic contrast in electropolymerized thin films of dioxythiophenes based conjugated polymers is known to be sensitive to the structure of monomer and the polymerizing conditions. However in our studies we found that it is also sensitive to the electrode surface wherein a significantly high electrochromic contrast is observed in the electropolymerized thin films of poly(3,4-ethylenedioxythiophene), PEDOT deposited on platinum (71%) as compared to that on indium tin oxide, ITO, coated glass surface (54%). This is attributed to the formation of more conjugated polymer on the metallic surfaces as confirmed by narrow and red shifted absorption peak for PEDOT on platinum compared to broad and blue shifted peak on ITO in the UV–vis absorption spectra. This difference in the electrochromic properties of electropolymerized PEDOT thin films on the two surfaces is investigated by studying their electrochemical growth using UV–vis absorption, Raman spectroscopy and atomic force microscopy techniques. These results suggest the deposition of more conjugated polymer in the initial stages of growth (≤3 mC/cm²) on both the substrates whereas it continues the same way into the intermediate stages (up to ∼15 mC/cm²) only on platinum, thereby, resulting in higher electrochromic contrast on platinum. The coloration efficiency of PEDOT thin film was also found to be improved on platinum (465 cm²/C) compared to that on ITO (230 cm²/C). Moreover, we observed that the EC contrast of electropolymerized PEDOT thin films on platinum was found to be insensitive to polymerizing solvent that is generally not the case when polymerized on ITO. The cyclic stability of PEDOT-Pt films are better compared to that of PEDOT-ITO which is attributed to the improved reversibility of these films with respect to potential switching.     

Preparation of Surfactants Directed PANI/In2O3 Nanocomposite Thin Films and Its NH3-Sensing Properties

Polyaniline/indium oxide(PANI/In2O3)nanocomposite thin films have been prepared in water-dispersed medium with the presence of different surfactants by an in-situ self-assembly technique.A cationic surfactant TTAB(tetradecyltrimethylammonium bromide)and a non-ionic surfactant tween20(poly(ethylene oxide)(20)sorbitan monolaurate)are used as additives.The nauocomposites and thin films are characterized by Fourier transform infrared(FTIR),transmission electron microscopy(TEM),and scanning electron microscopy(SEM),respectively.The optical properties reveal the Interaction between PANI/In2O3nanocomposites and surfactants,and PANI/In2O3 thin films prepared in the presence of surfaetants exhibits the finer nanofiber than the surfactants free PANI/In2O3thin film.The ammonia(NH3)gas-sensing characteristic of PANI/In2O3 thin films and the effect of different surfactants on the gas-sensing property are studied.The results indicated that the film processed in the presence of TTAB has the highest gas sensitivity among all the prepared films.     

A dual electrochromic film based on nanocomposite of aniline and o-toluidine copolymer with tungsten oxide nanoparticles

A dual electrochromic (EC) film was prepared based on composite of tungsten oxide nanoparticles and copolymer of aniline and o-toluidine, by electrochemical polymerization method. In this method, aniline and o-toluidine monomers were dispersed in the solution containing tungsten oxide (WO₃) nanoparticles and the final mixture was used for electrodeposition of film on fluorine doped tin oxide (FTO) coated glass. WO₃ nanoparticles were incorporated in the copolymer matrix structure, and a dual EC film was constructed. EC properties of WO₃, copolymer and WO₃-copolymer nanocomposite films were evaluated by cyclic voltammetry (CV) and the UV–Vis spectrophotometry. Also, the optical response and coloration efficiency (CE) of samples were investigated. The composition of organic-inorganic EC materials have improved properties in application of the EC film such as significant optical modulation (37.35% at 633 nm) and high switching speed and high coloration efficiency (116.6 cm² C⁻¹ at 633 nm). These achievements were better than WO₃ or copolymer films. The improved EC properties were appertained to the mixture of prominences of both materials.