Thermal conductivity studies on wool fabrics with conductive coatings

Methods of improving the thermal conductivity of wool fabrics have been investigated. Thermal conductivity measurement techniques, influence of synthesis parameters on the thermal conductivity of polypyrrole (PPy)-coated wool fabrics, and the relationship between electrical conductivity and thermal conductivity of PPy-coated wool fabrics are presented. An improvement in thermal conductivity was observed when fabrics were coated with the PPy. The thermal conductivity increased with the increase of pyrrole concentration and synthesis time. Anthraquinone-2-sulfonic acid and ferric chloride showed an optimal concentration for their influence on the thermal conductivity of the coated fabric. The improvement of thermal conductivity of wool fabrics is also investigated by Physical Vapor Deposition technique.

Effects of laundering on conductivity of polypyrrole-coated textiles

This study examines the resistance change in conductive polypyrrole-coated PET fabrics under the AS 2001.4.15 – 1994 laundering test conditions. The effects of individual detergent components of a standard detergent, including auxiliary chemicals, at four different temperatures were studied. When the coated fabric was washed under the AS 2001.4.15-1994 conditions, the ECE reference detergent and pure soap flakes (sodium sterate) both decreased the conductivity of the coating at a rate exponentially proportional to the laundering temperature. Detergent types had an influence over the rate of degradation; pH conditions had a large influence on the rate of polymer deterioration with the acidic nonionic detergent giving rise to significantly improved laundering conditions. The auxiliary chemicals, sodium carbonate and sodium perborate were seen to cause large degradation of polymers during laundering. Ethylene diamine tetra acetic acid was seen to have only a slight influence on the reduction of conductivity of polymers.

Characterization of conducting polymer coated fabrics at microwave frequencies

Purpose – The purpose of this paper is to investigate microwave reflection, transmission, and complex permittivity of p-toluene-2-sulfonic acid doped conducting polypyrrole coated nylon-lycra textiles in the 1-18?GHz frequency with a view to potential applications in the interaction of electromagnetic radiation with such coated fabrics.

Design/methodology/approach – The chemical polymerization of pyrrole is achieved by an oxidant, ferric chloride and doped with p-toluene sulfonic acid (pTSA) to enhance the conductivity and improve stability. Permittivity of the conducting textile substrates is performed using a free space transmission method accompanied by a mathematical diffraction reduction method.

Findings – The real part of permittivity increases with polymerization time and dopant concentration, reaching a plateau at certain dopant concentration and polymerization time. The imaginary part of permittivity shows a frequency dependent change throughout the test range. All the samples have higher values of absorption than reflection. The total electromagnetic shielding effectiveness exceeds 80 percent for the highly pTSA doped samples coated for 3?h.

Originality/value – A non-contact, non-destructive free space method thin flexible specimens to be tested with high accuracy across large frequency range. The non-destructive nature of the experiments enables investigation of the stability of the microwave transmission, reflection, absorption and complex permittivity values. Moreover, mathematical removal of the diffraction enables higher accuracy.

Synthesis, characterization and analytical modelling of mechanical behavior of a conducting polymer actuator

Electrochemical synthesis of a tri-layer polypyrrole based actuator optimized for performance was reported. The 0.05 M pyrrole and 0.05 M tetrabutylammonium hexaflurophosphate in propylene carbonate (PC) yielded the optimum performance and stability. The force produced ranged from 0.2 to 0.4mN. Cyclic deflection tests on PC based actuators for 3 hours indicated that the displacement decreased by 60%. PC based actuator had a longer operating time, exceeding 3 hours, compared to acetonitrile based actuators. A triple-layer model of the polymer actuator was developed based on the classic bending beam theory by considering strain electrode material. A tri-layer actuator was fabricated [4, 6], by initially sputter coating a PVDF film with approximately 100nm of gold layer, resulting in a conductive film with a surface resistance of 8-10Ω. The PVDF film was about ~145µm thick had an approximate pore size of 45μm. A solution containing 0.05M distilled pyrrole monomer, 0.05M (TBAPF6) and 1% (w/w) distilled water in PC (propylene carbonate) solution was purged with nitrogen for 15 minutes. The continuity between PPy and PVDF. Results predicted by the model were in good agreement with the experimental data.

Mechanisms governing the enhanced thermal stability of acid and base treated polypyrrole

One of the major problems associated with the use of polypyrrole (PPy) in a practical engineering application is its poor thermal stability at elevated temperatures, especially in the presence of oxygen and moisture. Several authors have shown that enhanced stability can be achieved through treatment with simple acids and bases. This paper presents a summary of the possible structural changes which occur as a result of these treatments and those that appear to be related to enhanced conductivity stability. A slight increase in conductivity (10–20%) is observed for acid treated PPy films which is found to be the result of protonation of the pyrrole structure. This effect is dramatically enhanced by treatment at high temperatures where an increase in conductivity of >84% can be achieved. Base treatment of the PPy films results in the deprotonation of the pyrrole structure leading to the loss of conductivity (>40%). Preliminary X-ray Photoelectron Spectroscopy (XPS) results indicate that both acid and base treatment resulted in the elimination of reactive sites for oxygen. Long term thermal ageing of these treated films were conducted at 150 °C in air. The conductivity decay behaviour was found to follow multiple first order chemical reaction kinetics.

A study of acid/base treatments of polypyrrole films using 13C n.m.r. spectroscopy

Electrodeposited polypyrrole films prepared with paratoluenesulfonate (pTS), dodecylsulfate (DDS) and perchlorate anions were treated with acidic and basic solutions, and their structure was investigated by 13C solid state n.m.r. spectroscopy. This technique has confirmed that pTS is completely removed from the film in both acidic and basic solutions whilst DDS is only partially removed and tends to decompose upon treatment with H2SO4. The appearance of shoulders at 143 ppm upon treatment with 0.5 M base indicates formation of a quinoid pyrrole structure. Substitution on the β-carbon by OH cannot be confirmed from the present spectra. Stronger base causes a more dramatic change in the polypyrrole backbone with an obvious increase in the electron density on the β-carbons, consistent with the reduction of the carbon backbone. There is no indication of quinoid units in this case. Acid treatments result in considerable broadening of the main 127 ppm polypyrrole peak.

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.

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.

Synthesis of 2-(selenophen-2-yl) pyrroles and their electropolymerization to electrochromic nanofilms

The divergent syntheses of 2-(selenophen-2-yl)pyrroles and their N-vinyl derivatives from available 2-acylselenophenes and acetylenes in a one-pot procedure make these exotic heterocyclic ensembles accessible. Now we face a potentially vast area for exploration with a great diversity of far-reaching consequences including conducting electrochromic polymers with repeating of pyrrole and selenophene units (emerging rivalry for polypyrroles and polyselenophenes), the synthesis of functionalized pyrrole–selenophene assembles for advanced materials, biochemistry and medicine, exciting models for theory of polymer conductivity.

Capsular polypyrrole hollow nanofibers: an efficient recyclable adsorbent for hexavalent chromium removal

Capsular polypyrrole hollow nanofibers (PPy-HNFs) were fabricated via in situ polymerization of pyrrole on an organic-inorganic template, followed by acid etching. Their application in removing hexavalent chromium (Cr(vi)) from aqueous solution was then investigated. The morphologies of the capsular PPy-HNFs were studied by both scanning electron microscopy (SEM) and transmission electron microscopy (TEM), which showed that the PPy-HNFs had a capsular structure in the walls of hollow nanofibers. Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) data confirmed the adsorption of Cr on capsular PPy-HNFs. The adsorption capacity increased with reduced pH of the initial solution and the adsorption process can be described using the pseudo-second-order model. These capsular PPy-HNFs showed a high Cr(vi) adsorption capacity up to 839.3 mg g-1. This adsorption capacity was largely retained even after five adsorption/desorption cycles. Electrostatic attraction between Cr and PPy-HNFs was studied using a proposed adsorption mechanism. The capsular PPy-HNFs formed a flexible membrane, which allowed easy handling during application. This study has demonstrated the possibilities of using this capsular PPy-HNF membrane for heavy metal removal from aqueous solution.

Fabrication of graphene foam supported carbon nanotube/polyaniline hybrids for high-performance supercapacitor applications

A large-scale, high-powered energy storage system is crucial for addressing the energy problem. The development of high-performance materials is a key issue in realizing the grid-scale applications of energy-storage devices. In this work, we describe a simple and scalable method for fabricating hybrids (graphenepyrrole/ carbon nanotube-polyaniline (GPCP)) using graphene foam as the supporting template. Graphene-pyrrole (G-Py) aerogels are prepared via a green hydrothermal route from two-dimensional materials such as graphene sheets, while a carbon nanotube/polyaniline (CNT/PANI) composite dispersion is obtained via the in situ polymerization method. The functional nanohybrid materials of GPCP can be assembled by simply dipping the prepared G-py aerogels into the CNT/PANI dispersion. The morphology of the obtained GPCP is investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), which revealed that the CNT/PANI was uniformly deposited onto the surfaces of the graphene. The as-synthesized GPCP maintains its original three-dimensional hierarchical porous architecture, which favors the diffusion of the electrolyte ions into the inner region of the active materials. Such hybrid materials exhibit significant specific capacitance of up to 350 F g^-1, making them promising in large-scale energy-storage device applications.

A non-fullerene electron acceptor based on central carbazole and terminal diketopyrrolopyrrole functionalities for efficient, reproducible and solution-processable bulk-heterojunction devices

A novel, solution-processable non-fullerene electron acceptor, 6,6′-((9-(heptadecan-9-yl)-9H-carbazole-2,7-diyl)bis(thiophene-5,2-diyl))bis(2,5-bis(2-ethylhexyl)-3-(thiophen-2-yl)-2,5-dihydropyrrolo[3,4-c]pyrrole-1,4-dione) (coded as N7), based on central carbazole and terminal diketopyrrolopyrrole building blocks was designed, synthesized and characterized. N7 displayed excellent solubility, thanks to its design allowing incorporation of numerous lipophilic chains, thermal stability, and afforded a 2.30% power conversion efficiency with a high open-circuit voltage (1.17 V) when tested with the conventional donor polymer poly(3-hexylthiophene) in solution-processable bulk-heterojunction devices. To our knowledge, not only is N7 the first reported chromophore based on carbazole and diketopyrrolopyrrole functionalities but the open-circuit voltage reported here is among the highest values for a single junction bulk-heterojunction device that has been fabricated using a simple device architecture, with reproducible outcomes and with no special treatment.