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Polyaniline (PANI) was attached onto the reduced graphene oxide (rGO) sheets through copolymerization of aniline with a para-phenylenediamine (PPD) functionalized graphene oxide (GO-PPD) using the poly(styrene sulfonate) (PSS) as the macromolecular dopant agent to produce a water-dispersible electrochromic material. The structures and the morphologies analysis confirm that the final electrochromic materials (rGO-PANI) are the mixture of PANI/PSS and the covalently bonded rGO-PANI (rGO-PANI hybrid). The rGO-PANI hybrid can be found to form a parallel arrangement to the substrate in the spin-coated film. This parallel arrangement of the layered two-dimensional nanostructure of rGO-PANI hybrid may narrow the ion transportation pathways of the exchanged ions, which will result in a high charge transfer resistance and slow switching speed. Meanwhile, with the conductive rGO added, the electrical conductivity of the electrochromic layer will be increased, which will benefit to low charge transfer resistance and high optical contrast. So the conductive two-dimensional nanostructure has a double-face influence on the electrochromic performances of PANI, which include a positive influence on the electrical conductivity and a negative influence on the ion diffusion. The overall influences depend on the loading amount of GO-PPD. With 4wt.% GO-PPD feeding, the optical contrast was enhanced by 36% from 0.38 for PANI/PSS to 0.52 for rGO-PANI-3, while the coloration time was almost same as that of PANI/PSS and the bleaching time was decreased by ~20% from 9.1s for PANI/PSS to 7.4s for rGO-PANI-3. The electrochemical tests showed that with the increasing of GO-PPD loading, the peak currents of cyclic voltammetry (CV) curves were increased, and the peak locations shifted to the positive potential for oxidation peak and the negative potential for reduction peak, respectively, which confirmed that the double-face influences of rGO-PANI on the electrochromic properties, including the enhanced electrochemical activities and the declined kinetic process. [ABSTRACT FROM AUTHOR]

A highly crystalline poly(2,5-dimethoxyaniline) (PDMA) nanoplate was synthesized via oxidative polymerization of 2,5-dimethoxyaniline (DMA) using poly(styrenesulfonate) (PSS) as dopant in a reaction system with low PSS concentration. The nanoplate formation conditions and the underlying mechanism were investigated. It is believed that the PSS/DMA complex has more extended conformation in the dilute aqueous system so that it can form parallel packed aggregates that act as a soft template for polymerization of DMA to form plate-like morphology. When PSS is replaced by p-toluene sulfonic acid (p-TSA) under the same conditions, only PDMA particles are formed because the p-TSA/DMA complex forms different shaped micelles. The structure and morphology of PDMA nanoplates were characterized using Fourier transform infrared spectroscopy, X-ray diffraction, selected area electron diffraction, scanning electron microscopy, atomic force microscopy, and transmission electron microscopy. The results show that the PDMA nanoplates of several nanometres in thickness are stacked together randomly and each nanoplate has a single crystal-like structure. [ABSTRACT FROM AUTHOR]

In this article, we report the synthesis, structures, morphologies, and electrochromic properties of covalently bonded polyaniline (PANI)−TiO2hybrids. The hybrids were synthesized via a sol−gel process, followed by oxidative polymerization, using a bifunctional compound to bridge the two phases. In comparison with PANI, the hybrids show significant enhancement in optical contrast and coloration efficiency. Furthermore, when covalently bonded to PANI, the TiO2nanodomains can act as electron acceptors, reducing the oxidation potential and band gap of PANI, and improving the long-term electrochromic stability. [ABSTRACT FROM AUTHOR]

Polymer electrolyte is an important component in many multilayer devices such as batteries, fuel cells, and electrochromic devices. The effects of polymer electrolyte solidification on the ionic movement and device performance are presented based on near-infrared (IR) (860−2500 nm) electrochromic (EC) devices using the conducting polymer polyaniline. EC devices using electrolyte with polar polymer host of P(VDF-TrFE) show stable and reversible light modulation up to 65% in gel state and 30% in solid state. This is significantly improved when compared to devices with solidified nonpolar polymer host which retains less than 10% light modulation. Electrochemical impedance combined with in situ light modulation measurement identifies various key characteristics exerted by the electrolyte states on device performance. Gel-state devices are affected by the amount of dissociated ions while ionic movement in the electrolyte bulk and through the electrolyte/EC material interface dictates the light modulation in semisolid devices. For solid-state devices, electronic leakage, ionic dissociation, and interaction with electrochrome molecules have been found to limit the operation. [ABSTRACT FROM AUTHOR]

Polyaniline (PANI)-tethered cubic polyhedral oligomeric silsesquioxane (POSS) in emeraldine base (EB) form is synthesized via oxidative copolymerization of octa(aminophenyl) silsesquioxane and aniline in the presence of HCl followed by the treatment with triethylamine. The chemical structures of POSS-PANI-EB are elucidated by Fourier transform infrared spectroscopy and elemental analysis. POSS-PANI/poly(2-acrylamido-methane-2-propanesulfonic acid) (PAMPS) multilayer thin films are successfully fabricated via layer-by-layer (LBL) assembly. Cyclic voltammetry studies show that the redox reactions in the thin film containing 50 POSS-PANI/PAMPS bilayers ((POSS-PANI/PAMPS)50) are close to non-diffusion-controlled processes in the studied scan-rate range of 10−100 mV/s, and the reactions are also more reversible than that in the linear counterpart (PANI/PAMPS)50. Under a dynamic switching condition of 40 s per cycle, the electrochromic contrast of (POSS-PANI/PAMPS)50is increased by more than 30% over that of (PANI/PAMPS)50and the switching time of (POSS-PANI/PAMPS)50is also significantly shorter than that of (PANI/PAMPS)50. In addition to the better control of film thickness and morphology, the electrochromic performance of the POSS-PANI/PAMPS multilayer films is also superior to the previously studied spin-coated thin films of POSS-PANI/polymeric acid complexes. The improvements can be attributed to the unique morphology brought by the synergistic combination of the starlike structure of POSS-PANI and the LBL assembly method, which allows for more favorable interactions between PANI chains and polymeric dopants as well as faster ion transport during the redox switching. [ABSTRACT FROM AUTHOR]

Orthorhombic YFeO3 thin film was prepared on La0.67Sr0.33MnO3/LaAlO3 substrate by a sol–gel spin-coating method. The structures of the YFeO3/La0.67Sr0.33MnO3/LaAlO3 (YFO/LSMO/LAO) sample were detected by x-ray diffraction pattern, Raman spectrometer, scanning electron microscopy, and atomic force microscope. The local ferroelectric polarization switching properties of the orthorhombic YFO film were confirmed by piezoresponse force microscopy (PFM) for the first time. The results show that the YFO film deposited on LSMO/LAO possesses orthorhombic structure, with ultra-fine crystal grains and flat surface. The leakage current of the YFO film is 8.39 × 10−4 A⋅cm−2 at 2 V, with its leakage mechanism found to be an ohmic behavior. PFM measurements indicate that the YFO film reveals weak ferroelectricity at room temperature and the local switching behavior of ferroelectric domains has been identified. By local poling experiment, polarization reversal in the orthorhombic YFO film at room temperature was further observed. [ABSTRACT FROM AUTHOR]