The influence of dopant permeability on electrochromic performance of polypyrrole films

Detailed characteristics of the electrochromic performance of polypyrrole films under electrochemical doping and dedoping are studied. The response time for colour change in polypyrrole films depends on the dopant permeability. The change in film colour occurring in the redox reaction of the film is investigated in detail as a function of the dopant electrolyte solution and the thickness of the polypyrrole film. Three colour states for polypyrrole films are demonstrated: yellow green, dark brown, and blue.     

Tuning of electrochromic properties by copolymerization of monoalkoxythiophenes and dialkoxythiophenes

Monoalkoxysubstituted and dialkoxysubstitued thiophene monomers were synthesized by the nucleophilic substitution and transetherification reactions. Electrochemical homopolymerization of 3‐octyloxythiophene (OOT) and 3,4‐dioctyloxythiophene (DOOT), copolymerization of OOT with DOOT were performed via potentiodynamic and potentiostatic methods in the supporting electrolyte. Both the copolymer and homopolymers were characterized via cyclic voltammetry, scanning electron microscopy, gel permeation chromatography, and spectroelectrochemical analysis. In the redox process of the polymers, it was linear relationship between the peak current and the scanning rate in their cyclic voltammograms. The copolymer of P(OOT‐co‐DOOT) showed obvious change of color between red and bright blue in reduced and oxidized states, that has a great difference with the homopolymers. The morphology studies indicated that the electrochemical deposition of P(OOT‐co‐DOOT) proceeds via a mechanism of nucleation and two‐dimensional growth. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Potentiometric properties of polypyrrole bilayers

The spatially separated polypyrrole (PPy) bilayers composed of easily (PPy/Cl) and heavily permeable (PPy/dodecylsulfate) for anions component layers have been prepared by consecutive electrodeposition. The set-up of quasi-equilibrium potential E_r during conditioning in the solution of electrolyte and the potentiometric response of bilayers to ions and redox system in the test solution were studied. The short-term potentiometric response of the bilayer system is mainly determined by the outer layer. The participation of the inner layer is related with permeability of the outer layer and with sensitivity of the inner layer to the ions of the test solution, and leads to the dependence of the electrode potential on the duration of the bilayer system’s exposure to the test solution.     

Star-like polyaniline prepared from octa(aminophenyl) silsesquioxane: Enhanced electrochromic contrast and electrochemical stability

We report the structures, electrochemical and electrochromic properties of organic-inorganic hybrid polymers prepared via copolymerization of octa(aminophenyl) silsesquioxane and aniline. Compared with homopolyaniline (PANI), this class of novel materials exhibits much greater thermodynamic penetrability in solution, as detected using static and dynamic light scattering, suggesting that they have a star-like molecular geometry. Due to their star-like geometry, in solid state the copolymers (POSS-PANI) exhibit a loosely packed structure with relatively low crystallinity, as evidenced by X-ray and TEM characterization, and hence relatively high ionic conductivity. Cyclic voltammetric studies show that POSS-PANI undergoes similar electrochemical reactions to that of PANI but its loosely packed structure allows slightly faster cation diffusion. Spectro-electrochemical studies show a ∼40% enhancement in electrochromic contrast brought by tethering PANI onto POSS, which can be attributed to more accessible doping sites in POSS-PANI. Furthermore, the electrochemical stability of POSS-PANI is also significantly improved over that of PANI. Infrared spectroscopic measurements indicate that the formation of electrochemically inactive quinonediimine is retarded in POSS-PANI possibly due to the increased conformation freedom of the dopant anions.     

An electrochromic device combining polypyrrole and WO3-I. Liquid electrolyte

In this work we assembled an electrochromic device using as active materials an organic conductive polymer and a transition metal oxide. We studied the materials used to assemble the device separately, and in complete devices. These materials were: polypyrrole doped with dodecylsulfate and tungsten oxide. The substrates used were glass slides coated with tin doped indium oxide, and the electrolyte was a propylene carbonate solution of lithium perchlorate. We adjusted the charge balance and the chromatic contrast of the devices by controlling the thickness of the polypyrrole films. To illustrate the results obtained, we describe two devices with different polypyrrole film thicknesses. The chromatic contrast in the visible and near-infrared wavelength range is 40% and the electrical and optical properties of the devices remain unchanged after 10⁴ double potential chronoamperometric steps.     

Gold nanocages: synthesis, properties, and applications

Noble-metal nanocages comprise a novel class of nanostructures possessing hollow interiors and porous walls. They are prepared using a remarkably simple galvanic replacement reaction between solutions containing metal precursor salts and Ag nanostructures prepared through polyol reduction. The electrochemical potential difference between the two species drives the reaction, with the reduced metal depositing on the surface of the Ag nanostructure. In our most studied example, involving HAuCl(4) as the metal precursor, the resultant Au is deposited epitaxially on the surface of the Ag nanocubes, adopting their underlying cubic form. Concurrent with this deposition, the interior Ag is oxidized and removed, together with alloying and dealloying, to produce hollow and, eventually, porous structures that we commonly refer to as Au nanocages. This approach is versatile, with a wide range of morphologies (e.g., nanorings, prism-shaped nanoboxes, nanotubes, and multiple-walled nanoshells or nanotubes) available upon changing the shape of the initial Ag template. In addition to Au-based structures, switching the metal salt precursors to Na(2)PtCl(4) and Na(2)PdCl(4) allows for the preparation of Pt- and Pd-containing hollow nanostructures, respectively. We have found that changing the amount of metal precursor added to the suspension of Ag nanocubes is a simple means of tuning both the composition and the localized surface plasmon resonance (LSPR) of the metal nanocages. Using this approach, we are developing structures for biomedical and catalytic applications. Because discrete dipole approximations predicted that the Au nanocages would have large absorption cross-sections and because their LSPR can be tuned into the near-infrared (where the attenuation of light by blood and soft tissue is greatly reduced), they are attractive materials for biomedical applications in which the selective absorption of light at great depths is desirable. For example, we have explored their use as contrast enhancement agents for both optical coherence tomography and photoacoustic tomography, with improved performance observed in each case. Because the Au nanocages have large absorption cross-sections, they are also effective photothermal transducers; thus, they might provide a therapeutic effect through selective hyperthermia-induced killing of targeted cancer cells. Our studies in vitro have illustrated the feasibility of applying this technique as a less-invasive form of cancer treatment.     

Electrorheological properties of thermo-oxidative polypyrrole nanofibers

Using a chemical oxidative polymerization, polypyrrole (PPy) nanofibers were synthesized. After further thermo-oxidative treatment in air, the conductivity of PPy nanofibers was adjusted to a suitable level for use as a non-conventional nanofiber-based electrorheological (ER) suspension. Under electric fields, rheological properties of thermo-oxidative PPy nanofiber suspension were characterized. It showed that the nanofiber suspension possessed notable ER effect and low current density. Especially, the yield stress and shear modulus of nanofiber suspension were stronger than that of conventional granular suspension at the same volume fraction though the off-field viscosity of former was lower than that of latter. The ER effect and current density of thermo-oxidative PPy nanofiber suspension depended on the thermo-oxidative time and the nanofibers obtained after treatment for 3-5 h at 240 °C exhibited the optimal ER performances. It also showed that the thermo-oxidative PPy nanofiber suspension could maintain good ER properties within a wide operating temperature range of 25-115 °C.     

Carbon nanocages grown by gold templating

A method for growing carbon cages using gold nanoparticles as templates is reported. Gold nanoparticles were deposited on carbon nanotubes (CNTs). The nanocages were grown on the gold particles by electrical Joule heating of the CNT. The gold was subsequently evaporated, leaving the cages intact. A special in situ TEM-holder equipped with a small scanning tunneling microscope was used as an electrical probe to drive current through the CNT, while the TEM was used for imaging of the entire growth process. The method might provide a general way for making carbon structures limited only by the shapes allowed by the fabrication methods of the gold nanostructures.     

Enhancing the performance of polypyrrole composites as electrode materials for supercapacitors by carbon nanotubes additives

In the framework of this study, a facile method to obtain polypyrrole (PPy)/carbon nanotubes composites is presented. Chemical polymerization of PPy directly on the carbon nanotubes allows to obtain a homogenous distribution of the polymer. A low amount of carbon additive, varying from 1.5 to 5.5 wt %, is applied in order to prevent the decrease of capacitance value due to the presence of a low-capacitance component and, at the same time, to protect the electrode material from mechanical changes during cycling electrical measurements. The electrochemical properties, such as capacitance, its retention at different current loads, cycling stability, or self-discharge, are discussed. Improvement of electrochemical performances of the synthesized materials is observed mostly during cyclic stability measurements and at high current regimes. The obtained results confirm that the addition of only 3% of carbon nanotubes provides the best electrochemical performances as electrode materials for supercapacitor application. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48867.     

添加聚乙烯醇改善三氧化钨电致变色薄膜性能的研究

为改善三氧化钨薄膜的电致变色性能,采用钨粉过氧化聚钨酸溶胶-凝胶法制备了添加聚乙烯醇的三氧化钨电致变色薄膜.采用扫描电镜、紫外可见分光光度计和CHI电化学工作站分别测定和分析了三氧化钨薄膜的微观结构、光透过性能和循环伏安特性.结果表明,添加一定量的聚乙烯醇可使薄膜的结构更加平整,变色更为均匀;在着色态、褪色态下的光透过率之差达到60%以上,变色可调范围变大.电致变色可逆性能和光谱性能较不添加聚乙烯醇有所提高.     

Investigation of mechanical and creep properties of polypyrrole by depth-sensing indentation

In this study, we used depth-sensing indentation (DSI) technique to investigate some mechanical properties (reduced elastic modulus, indentation hardness, and creep) of polypyrrole (PPy) conducting polymer obtained with different support electrolyte concentration. The influence of support electrolyte concentration on these parameters was also determined. The order of doping degree of the samples was determined by cyclic voltammetry. The indentation load–displacement curves of the samples were obtained under different peak load levels with a 70 s holding time at maximum load. Reduced elastic modulus and hardness values were determined by analysis of these curves using the Feng–Ngan (F–N) and Tang–Ngan (T–N) methods, respectively. Both reduced elastic modulus (E _r) and indentation hardness (H) exhibited significant peak load dependence, i.e., indentation size effect (ISE). It was found that both E _r and H values decreased as the support electrolyte concentration was increased. This was explained by an increase in the free volume as the doping degree was raised. The creep behavior of the samples was monitored from the load holding segment of the load–unload curves. It was found that creep increases with the increasing support electrolyte concentration.     

A solid-state electrochromic device based on complementary polypyrrole/polythiophene derivatives and an elastomeric electrolyte

A device was assembled using optically transparent glass electrodes and combining two complementary electrochromic polymeric materials, poly(4,4-dipentoxy-2,2-bithiophene) and poly(N,N-dimethyl-2,2-bipyrrole). As electrolyte we used an ionically conductive polymer; poly(epichlorohydrin-co-ethylene oxide) containing a lithium salt. The optical contrast in the visible/near infrared region, stability to repeated redox cycles and electrochromic efficiency are reported and discussed.     

Color rendering properties of light continuously modulated by an electrochromic switchable device

Every chromogenic switchable window gives rise to considerable change of spectral power distribution of the light crossing trough. The filtered light continuously changes during charging/discharging of the device, seen as its coloration/discoloration. As this process occurs continuously, it causes continuous change of colors on an illuminated multicolored scene. The ability of an electrochromic (EC) switchable unit to modulate daylight and different artificial lights passing through it is studied here. The color rendering properties of such a variable light are evaluated. The range of the effect and its consequences on the color of a scene can be adequately described by the change in chroma and hue angle during the modulation of light. These effects were evaluated by different light sources shining through the same EC unit. © 2009 Wiley Periodicals, Inc. Col Res Appl, 34, 321–329, 2009     

Electrical and microwave absorbing properties of polypyrrole synthesized by optimum strategy

The polypyrrole (PPy) was prepared by in situ solution polymerization. The structure and morphology were characterized by X‐ray diffractometry, scanning electron microscope (SEM), and transmission electron microscope, respectively. The electrical and dielectric properties of the PPy were measured by four‐point technique and impedance/materials analyzer. The results revealed that reaction time, reaction temperature, the types of doping agent, and the molar ratio of initiator to pyrrole monomer (n_APs/n_Py) had an important effect on electrical and dielectric properties of the PPy. It showed that the PPy doped with phosphoric acid and with n_APs/n_Py = 1 at 10°C for 12 h had better performance of electrical conductivity and dielectric loss. The PPy sample with 2 mm thickness had a minimum reflection loss value of ?19.68 dB at approximately 16 GHz and an available bandwidth of 6.2 GHz in the range of 8–18 GHz. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Conducting copolymers of polytetrahydrofuran and their electrochromic properties

Living polytetrahydrofuran (PTHF) was terminated with sodium thiophene methonate to yield a polymer with a thiophene group at one end. Copolymerizations of PTHF with pyrrole and thiophene were achieved in water‐p‐toluene sulfonic acid and acetonitrile‐tetrabutylammonium tetrafluoroborate (TBAFB) solvent‐electrolyte couples via constant potential electrolyses. Characterizations of the samples were performed by NMR, cyclic voltammetry, FT‐IR, thermal analyses, and scanning electron microscopy. Electrical conductivities were measured by the four‐probe technique. PTHF/PTh film that was deposited on ITO‐glass in a dichloromethane‐TBAFB solvent‐electrolyte couple was found to exhibit electrochromic behavior and it electrochemically switches between blue oxidized and red reduced states. Optical analyses were carried out to investigate the electronic structure of PTHF/PTh electrochromic copolymer. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 95: 1014–1023, 2005     

Electropolymrization and physicochemical properties of polypyrrole p-toluenesulfonate

Polypyrrole p-toluenesulfonate (PPTS) polymers were synthesized by the electrochemical technique from 0.2M pyrrole in 0:100, 1:99, 5:95, and 10:90 water/acetonitrile solutions containing 0.1M tetraethylammonium p-toluene sulfonate (TEATS) as a supporting electrolyte. Following the cyclic voltammetry measurements, the number of electrons involved in the reaction was determined to be unity. The results of thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) showed that the weight loss was most reapid in the temperature range from 533 K to 768 K, and the maximum value of the reaction rate was 0.27 mg/min at 651 K. From the temperature dependence of the electrical condutivity and electron spin responance (ESR) measurement, a small pallaron hopping conduction was suggested for PPTS polymers. © 1994 John Wiley & Sons, Inc.     

Effects of ethylene-acrylic acid ionomer on thermomechanical and electrochromic properties of electrochromic devices using gelatin-based electrolytes

Transparent adhesive polymer electrolytes, to be used for fabrication of electrochromic glass via a lamination process, were developed from gelatin blended with ethylene-acrylic acid (EAA) copolymer ionomer resin. The gelatin-based electrolyte films were prepared by mixing the polymer with glycerol, LiClO₄, formaldehyde, and EAA in a microcompounder. The concentration effect of EAA (i.e., 2.5, 5, 10, and 20 wt% with respect to the gelatin) on thermomechanical, optical, and electrochemical properties of the prepared films were then studied. Results from atomic force micrographs revealed that surface roughness of the neat gelatin film significantly decreased after blending with 20 wt% EAA. This corresponds to the highest ionic conductivity value (4.46 × 10⁻⁶ S/cm) of gelatin-based electrolyte in this study. Percentage light transmittance was also maintained above 80%, provided that the concentration of ionomer was kept below 20%. Finally, performance of the electrochromic device with a configuration of ITO/WO₃/gelatin/NiO/ITO was demonstrated. Coloration efficiency and response time of 60.38 cm²/C and 10 s/50 s (coloring/bleaching) were achieved, respectively.     

Improvement of the anticorrosion properties of polypyrrole by zinc phosphate pigment incorporation

A commercial zinc phosphate pigment was incorporated into polypyrrole (PPy) matrix during its electrochemical synthesis in order to improve the corrosion protection of polypyrrole on AISI 1010 steel. PPy/zinc phosphate composite films were synthesised in sodium salicylate medium with high current efficiency and containing 10% by weight of zinc and 4% by weight of phosphate. The influence of stirring and concentration of the electrolyte on the degree of pigment incorporation were investigated, as well as polymerisation time and applied current density. The morphology of the films was determined by scanning electron microscopy (SEM) and the distribution of pigment in the polymeric matrix was carried out by X-ray photoelectron spectroscopy (XPS). The PPy and PPy/zinc phosphate films were submitted to salt spray corrosion test, weight loss test and to electrochemical measurements like corrosion potential with time. In all tests, the composite films showed an enhancement in its protective action in comparison with PPy films.