Optimization of holographic polymer dispersed liquid crystal for ternary monomers

Polarized optical micrography (POM) images of gratings and UV–visible spectra of holographic polymer dispersed liquid crystals (HPDLC) are reported for a ternary monomer system composed of dipentaerythritol hydroxypentaacrylate/trimethylolpropanetriacrylate/N‐vinylpyrrolidone (DPHPA/TMPTA/NVP) = 7/2/1 by weight. Gratings were written by irradiation with an argon ion laser (λ = 488 nm) at various intensities (20–200 mW cm⁻²) on monomer/liquid crystal (LC) composite films of various compositions (75/25, 70/30, 65/35, 62/38, 60/40). Reflection efficiency–irradiation intensity–film composition relationships are obtained in three dimensional plots which show that maximum reflection moves from high LC content (38%) at low irradiation intensity (20 mW cm⁻²) to low LC content (25 wt%) at high irradiation intensity (200 mW cm⁻²). © 1999 Society of Chemical Industry     

Ionic liquid mediated magnesium ion conduction in poly(ethylene oxide) based polymer electrolyte

Magnesium ion conduction in poly(ethylene oxide) (PEO) based polymer electrolyte incorporated with room temperature ionic liquid (RTIL) is reported. The electrolyte films comprise the PEO complexed with magnesium trifluoromethanesulfonate (or magnesium triflate) added with different amount of ionic liquid, 1-ethyl-3-methylimidazolium trifluoromethanesulfonate (EMITf). The polymer electrolyte with ∼50 wt.% of ionic liquid offers a maximum electrical conductivity of ∼5.6 × 10⁻⁴ S cm⁻¹ at room temperature (∼25 °C) with improved thermal and electrochemical stabilities. The Mg²⁺ ion conduction in the PEO-complex is confirmed from cyclic voltammetry, impedance and transport number measurements. A significant increase in the Mg²⁺ ion transport number (tMg2+) is observed with increasing content of the ionic liquid in PEO–Mg salt complex and the maximum value is obtained to be ∼0.45 for ∼50 wt.% of ionic liquid. The interaction of imidazolium cations with ether oxygen of PEO, as evidenced from FTIR and Raman studies, play an important role in the substantial enhancement in the tMg2+ value.     

Synthesis and characterization of poly(1‐vinyl‐3‐propylimidazolium) iodide for quasi‐solid polymer electrolyte in dye‐sensitized solar cells

The synthesis conditions of ionic liquid 1‐vinyl‐3‐propylimidazolium iodide (ViPrIm⁺I⁻) and Poly(1‐vinyl‐3‐propylimidazolium) iodide [P(ViPrIm⁺I⁻)] were studied in this work. P(ViPrIm⁺I⁻) as a single‐ion conductor providing iodine was designed to develop a quasi‐solid polymer electrolyte based on PVDF/PEO film for dye‐sensitized solar cells (DSSCs). The samples were characterized respectively by high‐performance liquid chromatography (HPLC), Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance imaging (NMRI), gel permeation chromatography (GPC), etc. The results showed that the single‐ion conducting quasi‐solid polymer electrolyte (SC‐QPE) exhibited high ionic conductivity of 1.86 × 10⁻³ S cm⁻¹ at room temperature measured by CHI660C Electrochemical Workstation. Moreover, solar cells assembled using the SC‐QPE yielded an open‐circuit voltage of 0.83V, short‐circuit current of 8.01 mA cm⁻² and the conversion efficiency of 2.42%. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

High thermal conductivity of liquid crystalline monomer-poly (vinyl alcohol) dispersion films containing microscopic-ordered structure

The thermal conductivity of bulk polymers is usually very low, which is due to the amorphous domains where chains are randomly entangled, improving the degree of the chain alignment and forming a continuous thermal conduction network are expected to enhance the thermal conductivity. A series of liquid crystalline monomer-poly (vinyl alcohol) dispersion (MDLC) films with high thermal conductivity containing microscopic-ordered structure were prepared by introducing a highly ordered liquid crystalline monomer (LCM) exhibiting Smectic phase. The thermal conductivity of MDLC films was strongly related to the amount of LCM, which firstly increased and then decreased with the increase of LCM content. The thermal conductivity of MDLC film reached up to 1.20 W m⁻¹ K⁻¹ when the content of LCM was 15 wt% and rapidly decreased to 0.85 W m⁻¹ K⁻¹ as the content of LCM further increased to 25 wt%. LCM with low content (1–15 wt%) showed good fluidity, dispersity and interfacial compatibility in PVA molecular chains, which further increases the regularity of molecular chains alignment.     

Chitosan‐based gel film electrolytes containing ionic liquid and lithium salt for energy storage applications

Fabrication, characterization, and a comparative study have been performed for chitosan‐based polymer electrolytes using two different dispersion media. Chitosan gel film (solid) electrolytes are fabricated using acetic acid or adipic acid as the dispersant for chitosan in combination with ionic liquid and lithium salt. This quaternary system of chitosan, acetic acid or adipic acid, 1‐butyl‐3‐methylimadazolium tetrafluoroborate (ionic liquid), and lithium chloride is formed as an electrolyte for potential secondary energy storage applications. The ionic conductivities, thermal, structural, and morphological properties for these electrolytes are compared. The ionic conductivities for chitosan/adipic acid (CHAD) and for chitosan/acetic acid (CHAC) systems are in the range of 3.71 × 10⁻⁴−4.6 × 10⁻³ and 1.3 × 10⁻⁴ −3.2 × 10⁻³ S cm⁻¹, respectively. The thermal stability of CHAD‐based electrolytes is determined to be higher than that of CHAC‐based electrolytes. Preliminary studies are performed to determine the electrochemical stability of these materials as solid film electrolytes for electrochemical supercapacitors. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42143.     

Direct current electrical characterization of plasma polymerized pyrrole-N,N,3,5 tetramethylaniline bilayer thin films

The direct current conduction mechanism in plasma polymerized pyrrole-N,N,3,5 tetramethylaniline (PPPy-PPTMA) bilayer thin films has been discussed in this article. A parallel plate capacitively coupled glow discharge reactor was used to deposit PPPy, PPTMA, and PPPy-PPTMA thin films at room temperature onto glass substrates. The Fourier Transform Infrared analyses showed that the PPPy-PPTMA bilayer thin films contained the structural characteristics of both the PPPy and PPTMA. The current density-voltage characteristics of PPPy-PPTMA bilayer thin films of different deposition time-ratios indicated an increase in electrical conductivity as the proportion of PPTMA was increased in the bilayer films. It is also observed that the conductivity of the bilayer thin film is reduced compared with its component thin films. It is seen that in the low voltage region the current conduction obeys Ohm's law, while the charge transport phenomenon appears to be the space charge limited conduction in the higher voltage region. The mobility of the charges, the free charge carrier density, and the permittivity of the PPPy, PPTMA and PPPy-PPTMA bilayer thin films have been calculated. The permittivity for PPPy, PPTMA and PPPy-PPTMA bilayer thin films were found to be 1.07 × 10⁻¹⁰, 2.2 × 10⁻¹¹, and 1.26 × 10⁻¹⁰ C² N⁻¹ m⁻², respectively; the free charge carrier density were (3.56 ± 0.01) × 10²², 2 × 10²¹ and (5.19 ± 0.02) × 10²² m⁻³ respectively; and the mobility of the charges were found to be (4.4 ± 0.01) × 10⁻¹⁹, 1.3 × 10⁻¹³ and (2.1 ± 0.01) × 10⁻¹⁹ m² V⁻¹ s⁻¹ respectively. PACS: 72.80.Le, 73.21.Ac, 73.40.Rw, 73.50.Gr, 73.61.Ph. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Highly anisotropic thermal conductivity of mesogenic epoxy resin film through orientation control

To develop insulating materials with a high thermally conductive anisotropy, planarly aligned mesogenic epoxy (ME) resin film was fabricated by uniaxial coating on a hydrophobic polyethylene terephthalate substrate. Grazing incidence small-angle X-ray scattering (GISAXS) and transmission SAXS measurements exhibited that the films spontaneously formed uniaxially aligned monodomain-like smectic structures by curing on the hydrophobic substrate. Then, an in- and out-of-plane thermal conductivity of 10 and 0.048 W m⁻¹ K⁻¹ and outstanding thermal conductivity anisotropy of 208 have been confirmed, respectively. The ME resin films with high thermal conductivity can be applied as insulating materials for multiple-layer electrical and electronic devices.     

PIN/PAN聚合物基电解质膜的制备及性能

利用静电纺丝技术制备了聚吲哚/聚丙烯腈(PIN/PAN)聚合物基电解质膜,代替纸基铝空气电池中的纤维素纸(C-P),并应用于固态铝空气电池。探究了PIN含量对电解质膜离子电导率及吸液率的影响。采用SEM和FTIR对PIN/PAN聚合物基电解质膜表面形貌及化学组成进行分析。借助电化学工作站和电池测试系统,分析了电解质膜离子电导率及固态铝空气电池放电特性。结果表明,采用PIN/PAN聚合物基电解质膜可有效提升固态铝空气电池性能,在3 mA.cm_^-2、5 mA.cm_^-2、7 mA.cm_^-2电流密度下,放电时长比纸基铝空气电池分别提升了21%、27%、34%,且放电时长与电解质膜的吸液率及离子电导率相关。其中4%PIN/PAN聚合物基电解质膜离子电导率可达6.7×10_^-4 S.cm_^-1,同时对碱性溶液具有良好的吸附能力,吸液率最高可达496%,为纤维素纸的3.2倍。     

Effective photopolymerization of C60 films under simultaneous deposition and UV light irradiation: Spectroscopy and morphology study

An effective method for uniform photopolymerization of C₆₀ films using simultaneous deposition and irradiation with ultraviolet (UV) light is described. The photopolymerization process was monitored as a function of irradiation time using Raman and infrared (IR) spectroscopy. New features appeared in the Raman (near the pentagonal pinch A_g(2) mode) and IR spectra (400-1500 cm⁻¹) after more than 20 h of UV irradiation testifying to the transformation of pristine C₆₀ to polymerized C₆₀ phases. Band shape analysis of the vibrational data revealed: (i) the degree of photopolymerization to be ∼90% after 20 h of irradiation, and (ii) the presence of orthorhombic, tetragonal, and rhombohedral phases in the photopolymerized films. Electron microscopy and diffraction studies revealed the amorphous nature of the photopolymerized films which comprised of crystals with a linear dimension of ∼40-60 nm. No evidence for cracks in the surface of the polymerized film was found. The proposed route for photopolymerization provides an opportunity to prepare extended polymeric C₆₀ films suitable for technological applications.     

Preparation and properties of conducting arachidic acid/polypyrrole composite langmuir–blodgett films

Electrically conducting arachidic acid/polypyrrole (PPy) composite films were prepared by exposing the arachidic acid LB films containing ferric chloride to pyrrole vapor. The optimum conditions to deposit matrix LB film were the subphase temperature of 23–25°C, pH of 6.0 and ferric chloride concentration of 5.0 × 10⁻⁵ M. The formation of PPy in the arachidic acid matrix LB films was confirmed by UV-visible spectra, FTIR spectra, and scanning electron micrographs. The average thickness of the composite LB films prepared at 0°C was 1525 Å. The composite films prepared at lower temperatures have more uniform surface and exhibit higher electrical conductivity than the films prepared at higher temperatures do. The in-plain conductivity and the transverse conductivity of the composite film were 10⁻³−10⁻² S/cm and 10⁻⁶S/cm, respectively, and, thus, the conductivity anisotropy was about 10³ © 1996 John Wiley & Sons, Inc.     

Electrochromic switching and nanoscale electrical properties of a poly(5-cyano indole)-poly(3,4-ethylenedioxypyrrole) device with a free standing ionic liquid electrolyte

Poly(5-cyano indole) or PCIND and poly(3,4-ethylenedioxy pyrrole) or PEDOP films have been electro-synthesized for the first time in a hydrophobic ionic liquid: trihexyl(tetradecyl)phosphonium tris(pentafluoroethyl)trifluorophosphate. PCIND, is an anodically coloring electrochrome, and exhibited a reversible switching between a transmissive yellow and a saturated green hue, with an absorption maximum at 650 nm in the fully oxidized state. Conducting atomic force microscopy studies revealed the PCIND film to be composed of an ensemble of segregated high current islands with a nanoscale electronic conductivity of 0.1 S cm⁻¹ and a band gap of 1.41 eV. The cathodically coloring PEDOP film comprised of uniformly distributed and inter-connected high current carrying domains with a band gap of 1.82 eV and a conductivity of 5.4 S cm⁻¹. Prototype electrochromic devices were fabricated using PEDOP and PCIND as cathode and anode with a thermally stable ionic liquid based, free standing polymeric gel film with a high ionic conductivity of 1.19 × 10⁻³ S cm⁻¹ as the electrolyte. The device showed large coloration efficiencies of 480 and 796 cm² C⁻¹ at visible and NIR wavelengths of 475 and 1100 nm respectively which far exceeded the coloration efficiencies of the individual electrochromes, thereby demonstrating the synergy between the two colorants. The performance attributes of the device, which switched reversibly between red, green and blue hues, are an outcome of an interplay between the high nanolevel electron conduction capabilities (enable fast charge transport) and high ion storage capacities (increase optical contrast as more number of electrochemically addressable sites are accessed by the electrolyte ions) of the PEDOP and PCIND films. Our studies demonstrate the applicability of PCIND films as anodic electrochromes in energy efficient windows.     

Oxide film growth on Al-In alloys in a borate buffer solution in conditions of galvanostatic anodising

Anodic oxide films have been formed galvanostatically on Al-In alloys (containing up to 0.074% In) in a borate buffer solution (pH 7.8) at different current densities (20-100 μA cm⁻²). The mechanism, kinetics of growth and properties of formed oxide films have been investigated. The study of charge curves suggests that the growth of oxide films on Al-In alloys occurs by an activation-controlled ionic conduction under the influence of the high electric field through the oxide film according to an exponential law, like on valve metals. The following parameters have been calculated: the constants of the exponential law, ionic conductivity through the film, the effective activation distance for ion movement and the corresponding field strength. The values for the field strength, of the order of magnitude of 10⁶ V cm⁻¹, justify the application of the high field migration mechanism. Properties of anodic oxide films have been determined by means of electrochemical impedance spectroscopy; the resistance and thickness of the oxide film have been found to increase with the increase in the indium content in the alloy and with increased anodic current density. It has been established that the current efficiency in oxide films formation on Al-In alloys is lower than 100%: the increase of the indium content in the alloy, as well as the increase in anodic current density, increases the value of current efficiency.     

Highly ion conductive flexible films composed of network polymers based on polymerizable ionic liquids

Ionic liquid-type polymer brushes having different hydrocarbon (HC) chain lengths between polymerizable group and imidazolium ring were synthesized. When the carbon number of HC chain was 6, the ionic liquid-type polymer brush exhibited the highest ionic conductivity of 1.37×10⁻⁴ S cm⁻¹ at 30 °C, reflecting low T_g of −60 °C. Moreover, for the first time, we succeeded in obtaining transparent and flexible films without considerable decrease in the ionic conductivity as compared with that of corresponding monomers by using suitable cross-linkers. The most ion conductive (1.1×10⁻⁴ S cm⁻¹ at 30 °C) film was obtained when tetra(ethylene glycol)diacrylate was used 0.5 mol% to ionic liquid monomer as the cross-linker. This film is one of excellent conductive films among single-ion conductive materials.     

Novel electrolyte system: Porous polymeric support filled with liquid electrolyte

In this article, a novel electrolyte system composed of both porous polysulfone film and a propylene carbonate/LiCIO₄ liquid solution occupying the pore is suggested. Porous poly-sulfone acts as a support which imparts a good mechanical property and accommodation of a liquid electrolyte. Using this approach, we could enhance the conductivity and me-chanical property of the polymer electrolyte simultaneously. The maximum conductivity of this system was 3.93 × 10⁻³ S/cm at room temperature. The conductivity seems to be significantly affected by the amount of the uptake of the liquid electrolyte and also by the surface characteristics of the porous polysulfone. The path for ionic conduction is effectively formed with the increase in the uptake of the liquid electrolyte. Low-surface porosity and high-surface roughness is believed to reduce the ionic conduction. However, the denser surface layer of the support showed retarded evaporation of propylene carbonate under reduced pressure, indicating superior long-term stability. © 1996 John Wiley & Sons, Inc.     

Thermal analysis of submicron nanocrystalline diamond films

The thermal properties of sub-μm nanocrystalline diamond films in the range of 0.37–1.1 μm grown by hot filament CVD, initiated by bias enhanced nucleation on a nm-thin Si-nucleation layer on various substrates, have been characterized by scanning thermal microscopy. After coalescence, the films have been outgrown with a columnar grain structure. The results indicate that even in the sub-μm range, the average thermal conductivity of these NCD films approaches 400 W m^− 1 K^− 1. By patterning the films into membranes and step-like mesas, the lateral component and the vertical component of the thermal conductivity, k_lateral and k_vertical, have been isolated showing an anisotropy between vertical conduction along the columns, with k_vertical ≈ 1000 W m^− 1 K^− 1, and a weaker lateral conduction across the columns, with k_lateral ≈ 300 W m^− 1 K^− 1.     

A novel polymeric gel electrolyte systems containing magnesium salt with ionic liquid

A new polymeric gel electrolyte system consisting of poly(ethylene oxide)-modified polymethacrylate (PEO-PMA) with organic ionic liquid dissolving magnesium salt, Mg[(CF₃SO₂)₂N]₂, has been developed. The ionic conductance and electrochemical properties of the gel films were investigated. The obtained gel film was self-standing, transparent and flexible with sufficient mechanical strength. Thermal analysis of the gel film showed that it is homogeneous and amorphous over a wide temperature range. The highest conductivity, ca. 3.5 mS cm⁻¹ at 60 °C, was obtained for the polymeric gel containing 80 wt.% of the liquid component that consists of 80 mol% of EMITFSI (1-ethyl-3-methylimidazolium bis(trofluoromethylsulfonyl)imide) and 20 mol% of Mg[(CF₃SO₂)₂N]₂. The sort of the ionic liquid affected much on the ionic conductivity of the gel. The dc polarization of a Pt/polymeric gel electrolyte/Mg cell proved that the magnesium ion (Mg²⁺) can mobile in the present polymeric gel system.     

Ionic conduction of novel polymer composite films based on partially phosphorylated poly(vinyl alcohol)

New ion-conducting polymer composite films have been prepared, and their ionic conducting properties have been investigated. The polymer composite films are fabricated from partially phosphorylated poly(vinyl alcohol) with tetramethylammonium salt (P-PVA·Me₄N⁺) and poly(acrylic acid) (PAA) or poly(ethylene glycol) (PEG). For P-PVA·Me₄N⁺/PEG composite films, the ionic conductivity and carrier density sharply increased, and carrier mobility sharply decreased around [PEG]/[PO₃]_P-PVA of 2. The ionic conductivity is dominated by both carrier density and carrier mobility at [PEG]/[PO₃]_P-PVA<2 and only by carrier density at [PEG]/[PO₃]_P-PVA>2. This is attributed to the fact that the ionic conduction in P-PVA·Me₄N⁺/PEG composite films occurred through the PEG-Me₄N⁺ complex which was independent of the carrier mobility. On the other hand, the ionic conductivity in P-PVA·Me₄N⁺/PAA composite films showed a bell-shaped dependence on the PAA contents with a maximum value at [CO₂H]_PAA/[OH]_P-PVA=1. FTIR spectrum measurements demonstrated that part of the carboxylic acid residues was dissociated in the composite films. This fact implied that the ionic conduction was mediated by PAA at the low PAA content. At high PAA content, however, an excess of the carboxylic acid residues formed trapping sites for the Me₄N⁺ ion, leading to a decrease in the ionic conductivity. Furthermore, we proposed a unique mechanism of the ionic conduction.     

Enhanced ion transport in polymer–ionic liquid electrolytes containing ionic liquid-functionalized nanostructured carbon materials

An effective chemical strategy for the synthesis of polymer–ionic liquid (IL) electrolytes with ion-conducting channels, physically modulated by variously dimensioned IL-functionalized carbon materials (IL-FCMs) including carbon black (CB), multi-walled carbon nanotubes (MWCNT) and reduced graphene oxide sheets (RGO) is reported, enabling a fundamental understanding of the relationship between carbon structures and ion transport behavior. The risk of electrical shorts is eliminated by the presence of IL groups on the surfaces of CMs and only minimal amounts of the IL-FCMs (⩽1.0 wt.%) in the polymer/IL composite electrolytes (e.g., polymer matrix filled with 1.0 wt.% IL-FCMs has a conductivity of ∼10⁻⁷ S cm⁻¹ at 100 °C). Increase in ion transport within the reorganized ion channels of the composite polymer electrolytes (CPEs) is confirmed by the enhanced ionic conductivity and low activation energy for through-plane and in-plane ionic conduction at different temperature (40–160 °C). Maximum improvement in the ionic conductivity (150–300% at 100 °C) can be achieved by optimizing the carbon structure and the loading ratio, which leads to highly ionic conductive polymer/IL composite electrolytes for practical applications.     

Investigation of electromechanical distortions in gallium nitride by reflectance anisotropy spectroscopy

Real time reflectance spectroscopy has been used to investigate the extent and development of dielectric anisotropy during chemical beam epitaxy of gallium nitride on a GaAs(001) substrate using a low temperature aluminium nitride buffer layer. Reflection anisotropy between the [1&#x0304;10] and [110] directions indicates a strong cubic symmetry with bulk anisotropic strains of the order of 0.001. Post-growth reflectance measurements have been made to investigate electromechanical distortions in the gallium nitride epilayer when an electric field was applied in the [001] direction. The d₁₄ piezoelectric modulus of cubic gallium nitride is estimated to be 1.95 pm V⁻¹. Reflectance anisotropy spectroscopy is shown to be a sensitive method for the measurement of electromechanical effects in thin films, and in particular a novel method for investigating thin film semiconductor piezoelectric materials.     

High temperature ionic conduction mediated by ionic liquid incorporated within the metal-organic framework UiO-67(Zr)

IL@MOF (IL = ionic liquid; MOF = metal organic framework) as a new type hybrid ionic conductor has attracted research interest. Ionic liquids incorporated within MOFs not only promote the ionic conductivity of ILs, but also mediate the working temperature. In our report, 1-Ethyl-3-methylimidazolium Chloride (EMIMCl) was introduced into the pores of UiO-67(Zr) MOF by taking simple strategy basing on capillary action through specific grinding and diffusing in heating process. The working temperature of EMIMCl@UiO-67 is up to 200 °C. And it shows high ionic conductivity (1.67 × 10^− 3 S·cm^− 1 at 200 °C). The activation energy was estimated to be 0.37 eV. It is noteworthy that the hybrid material can be regarded as a fast-ion conductor based on the value of high conduction and low E_a. The high-temperature and humidity-independent ion conduction as well as low activation energy make this material potentially useful for electrochemical devices.