Conducting polymer electrochemistry in ionic liquids

Applications of polymers like polypyrrole and polythiophene often require interaction with an electrolyte consisting of solvent and dissolved salt. Ionic Liquids (ILs) are pure saits, fluid at room temperature, that form charged electrolytes. Pure l-Bu-3-Me-Imidazolium PF₆ (BMI PF₆) a hydrophobic IL that has a wide potential window, was used to investigate the electrochemistry ofpolypyrrole. Enhanced electrochemic~l stability of polypyrrole was obtained on repetitive redox cycling with respect to the equivalent propylene carbonate electrolyte with tetrabutylammonium hexaflurophosphate (TBA PF₆) electrolyte.

Polymer-ceramic ion-conducting composites

Composites of a Li⁺ ion-conducting ceramic powder in a polyether-based elastomeric electrolyte matrix are described. At 66 wt.% of ceramic the composite can be prepared as a paste and cured into a coherent material having useful elastic and tensile properties. The total conductivity of the composite was found to be (1.9 ± 0.2) × 10⁻⁴ S cm⁻¹ at 40 °C which was approximately 1 order of magnitude higher than the polymer electrolyte component alone. The result was also approximately 1 order of magnitude higher than the total conductivity of the ceramic powders tested in this work.

Solid state NMR characterization of lithium conducting ceramics

⁷Li solid state NMR has been used to characterize lithium aluminium titanium phosphate and lithium lanthanum titanate ceramics. Both materials have high ionic mobilities at room temperature and this is reflected in their static ⁷Li powder patterns. In the case of the phosphate based ceramic, a narrow Lorentzian peak is observed above 300 K, which narrows further with increasing temperature. The accompanying quadrupolar structure, with C_Q (quadrupolar coupling constant) ~ 40 kHz, suggests that the lithium ions are hopping rapidly between equivalent, high electric field gradient sites. The ²⁷Al and ³¹P magic angle spinning (MAS) spectra reveal an asymmetric phosphorus peak and two distinct aluminium resonances. The room temperature powder pattern of Li_0.33La_0.57TiO₃ shows a dipolar broadened peak which narrows quite suddenly at 310 K revealing quadrupolar satellites with C_Q ~ 900 Hz. A second lithium site is also observed in this material, as indicated by a further, weaker quadrupolar structure (C_Q ~ 40 kHz).

Conducting polymers with fibrillar morphology synthesized in a biphasic ionic liquid/water system

The synthesis of poly(pyrrole), poly(terthiophene), and poly(3,4-ethylenedioxythiophene) with unusual fibrillar morphologies has been achieved by chemical polymerization in a biphasic ionic liquid/water system. Use of aqueous gold chloride as the oxidant, with the monomers dissolved in a hydrophobic ionic liquid, allows the polymerization to occur at the ionic liquid/water interface. The resultant conducting polymer fibrils are, on average, 50−100 nm wide and can be thousands of nanometers long. The polymers produced in this ionic liquid system are compared to those synthesized in a biphasic chloroform/water system.

One-step synthesis of conducting polymer–noble metal nanoparticle composites using an ionic liquid

Conducting polymers containing incorporated gold or silver nanoparticles have been synthesized using ionic liquid solutions of gold chloride or silver nitrate. Use of the metal salts as the oxidant for monomers such as pyrrole and terthiophene allows the composites to be formed in one simple step, without the need for templates or capping agents. The incorporated metal nanoparticles are clearly visible by TEM, and the composites have been further analyzed by TGA, CV, UV-Vis, Raman, XPS and scanning TEM coupled with EDS analysis. Utilization of an ionic liquid allows the full oxidizing power of the gold chloride to be accessed, resulting in incorporation of metallic gold into the polymers.

Dielectric properties of conducting polymer

The dielectric properties of conducting polymer composites containing polypyrrole (PPy) crushed films, PPy powder, polyaniline (PAn) base and acid powders as the dispersants and silicone rubber and vinyl ester as matrix materials have been investigated in the frequency range 2-18 GHz. The dielectric parameters such as the real part, epsiprime, and imaginary part, epsiPrime, of the permittivity and loss tangent, tandelta, increase with increasing conductivity and concentration of the dispersant. The geometrical shape of the dispersant governs the ability of conductive network formation which is indicated by a large drop in the resistivity of the composite. Also, dispersant/matrix interactions and physical properties of the matrix influence the agglomeration of the dispersant phase which, in turn, affects the dielectric properties of the composites. Flakes of PPy obtained by crushing highly conductive films and large PAn powder aggregates were unable to form a conducting network. The composites without a network of dispersant exhibit low dielectric parameters. On the other hand, high values of tan delta ranging from 0.7–1.1 were achieved for the PPy powder (15 parts)/silicone rubber composites where a conducting network was observed.

High current density and drift velocity in templated conducting polymers

Conducting polymers prepared by a templated vapour phase polymerisation process involving solid phase transition metal complexes are found to produce polymers with charge carriers that exhibit maximum drift velocity in the range of 1 m/s. This super-mobility seems to be related to a high degree of ordering in the materials as evidenced by the X-ray diffraction data. This may result from a templated polymerisation process. The high mobility manifests itself as a capacity to sustain very high current densities (>10000 A/cm2); such high current densities are of importance in thin film conductor applications.

A new class of proton-conducting ionic plastic crystals based on organic cations and dihydrogen phosphate

Choline dihydrogen phosphate ([N_1.1.1.2OH]DHP) and 1-butyl-3-methylimidazolium dihydrogen phosphate ([C₄mim]DHP) were synthesized as a new class of proton-conducting ionic plastic crystals. Both [N_1.1.1.2OH]DHP and [C₄mim]DHP showed solid–solid phase transition(s) and showed a final entropy of fusion lower than 20 J K⁻¹ mol⁻¹ which is consistent with Timmerman’s criterion for molecular plastic crystals. The ionic conductivity of [N_1.1.1.2OH]DHP was in the range of 10⁻⁶ S cm⁻¹–10⁻³ S cm⁻¹ in the plastic crystalline phase. On the other hand, the ionic conductivity of [C₄mim]DHP showed about 10⁻⁵ S cm⁻¹ in the plastic crystalline phase. [N_1.1.1.2OH]DHP showed one order of magnitude higher ionic conductivity than [C₄mim]DHP in the temperature range where the plastic phase is stable.

Conducting polymer composite materials for hydrogen generation

A novel conducting polymer/non-conducting polymer composite (PEDOT/PEG), produced by vapor phase polymerization of PEDOT in the presence of PEG, shows stable electrocatalytic reduction of protons to hydrogen with conversion currents and over-potential comparable to platinum. The swelling of the composite by PEG and especially its ability to coordinate protons seems to be essential for the catalytic activity of the composite.

Ion effects in REDOX cycling of conducting polymer based electrochromic materials

Conducting polymer based electrochromic devices were assembled with various ionic liquid (IL) based electrolytes to probe the role of the ion structure on electrochromic performance. When the IL contained the same anion as the dopant ion used in the conducting polymers an enhanced electrochromic performance was observed providing high photopic contrast at low applied potential.

Visible transparent, UV-blocking polymer nanocomposite films containing nano-sized organic-LDH (Layered Double Hydroxide) hybrid

A nano-sized Mg2Al layered double hydroxide (LDH) was used for encapsulating an organic UV absorber, 2-hydroxy-4- methoxybenzeophenone-5-sulfonic acid (HMBS), to produce HMBS@LDH hybrid nano-platelets. Upon dispersing this organic-inorganic hybrid LDH into ethylene-vinyl alcohol copolymer (EVOH) for film casting, a thin polymer
nanocomposite film that is UV opaque but highly transparent to visible light (higher than 90%) was formed. Thermogravimetry (TG) analysis confirmed that the intercalation of HMBS into LDH considerably increased the thermal stability of HMBS. Such an improvement was attributed to the strong guest-host interaction between the HMBS anions and the LDH layers. Also, the nanocomposite films were flexible and had good mechanical properties.

Reflections on conducting educational research projects in Papua New Guinea

This article discusses how work on an AusAID-funded impact study of major elementary school reforms influenced the research design of a subsequent Australian Development Research Award project investigating the development of sustainable professional learning communities for primary school teachers in remote places of PNG. The authors reflect on how their different backgrounds, roles, experiences and expertise influenced the design and conduct of the projects and, in particular, how the experiences of the action research and survey methods used on the first project shaped the design of the second. The participating elementary school teachers were encouraged, through action research approaches, to develop self reflexive attitudes to their professional work, and to engage in critical reflection of their roles and practices. Accordingly, this article adopts a self-reflexive position towards the authors’ work as academics and researchers as they endeavoured to produce methodologies that are academically rigorous, contextually suitable, and epistemologically appropriate for PNG.

Synthesis of silica-coated ZnO nanocomposite : the resonance structure of polyvinyl pyrrolidone (PVP) as a coupling agent

Abstract The preparation of silica-coated ZnO nanocomposite using polyvinyl pyrrolidone (PVP) as a coupling agent was investigated. Transmission electron microscopy analysis revealed that silica has been deposited on the surface of PVP-capped ZnO nanoparticles as a continuous thin layer. Two-dimensional correlation analysis based on the time-dependent UV–vis spectra was introduced to study the interaction governing the deposition of silica on to PVP-capped ZnO. Strong hydrogen bonds formed between the amphiphilic PVP molecules and silica in the silicacoated PVP-capped ZnO composites. The reduced photocatalytic activity of silica-coated ZnO nanoparticles will enhance their performance as durable, safe, and nonreactive UV blockers in plastics, paints, and coating for outdoor textile and timber products.

Ionic liquid-assisted synthesis of polyaniline/gold nanocomposite and its biocatalytic application

In this report, a novel chemical synthesis of polyaniline/gold nanocomposite is explored using ionic liquid (IL) 1-Butyl-3-methylimidazolium hexafluorophosphate. The direct chemical synthesis of polyaniline/gold nanocomposite was initiated via the spontaneous oxidation of aniline by AuCl4 − in IL. A nearly uniform dispersion of polyaniline/Au particles with a diameter of 450 ± 80 nm was produced by this method, which indicates that this method is more suitable for controlling particle dimensions. It was also found that the electrical conductivity of the polyaniline/gold nanocomposite was more than 100 times higher than that of the pure polyaniline nanoparticles. The polyaniline/gold nanocomposite displays superior function in the biocatalytic activation of microperoxidase-11 because of the high surface area of the assembly and the enhanced charge transport properties of the composite material. We also report the possible application of polyaniline/gold nanocomposite as a H2O2 biosensor.

Synthesis and characterization of soluble conducting polymers

Although conducting polymers have various potential applications, lack of solubility is an impediment in their direct application to material surfaces. Synthesis of alkyl pyrrole monomers and subsequent polymerization into soluble conducting polymers are aimed as alternatives to conventional methods of application of conducting polymers on substrates. Alkyl chains are attached to a pyrrole ring to produce solubility in the resulting conducting polypyrroles, which allow direct application of conductive polymer emulsions to any desired surface. Friedel-Crafts acylation of the tosyl-protected pyrrole provides high yields of the 3-acylated product. The conductivity values of poly-3- and 3, 4-substituted pyrroles are generally less than the unmodified polypyrrole. Increasingly bulkier groups attached to the pyrrole means lower conductivity of the resultant polymer. As the carbon chain length attached to the 3-position of pyrrole increases, the solubility also increases. However, the magnitude of change in conductivity of films and pellets of soluble conducting polypyrroles over the alkyl range is not significant.