Facile one‐step synthesis of electromagnetic functionalized polypyrrole/Fe3O4 nanotubes via a self‐assembly process

This article reports a simple self‐assembly process for facile one‐step synthesis of novel electromagnetic functionalized polypyrrole (PPy)/Fe₃O₄ composite nanotubes using p‐toluenesulfonic acid (p‐TSA) as the dopant and FeCl₃ as the oxidant. The key trick of the present method is to use FeCl₃ as the oxidant for both PPy and Fe₃O₄ in the same time to synthesize PPy/Fe₃O₄ composite nanotubes in one‐step. This facile one‐step method is much simpler than the conventional approach using the Fe₃O₄ nanoparticles as the additives. Compared to the similar composites synthesized using the conventional method, the as‐prepared PPy‐p‐TSA/Fe₃O₄ composite nanotubes using the facile one‐step self‐assembly process show much higher room‐temperature conductivity. Moreover, the composite nanotubes display interesting ferromagnetic behavior. The electrical properties of the PPy‐p‐TSA/Fe₃O₄ composite nanotubes are dominated by the amount of FeCl₃ while their magnetic properties are controlled by the amount of FeCl₂. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 320–326, 2010     

Enhanced differentiation of embryonic and neural stem cells to neuronal fates on laminin peptides doped polypyrrole

PPy is a conducting polymer material that has been widely investigated for biomedical applications. hESCs and adult rNSCs were grown on four PPy surfaces doped with PSS or peptide from laminin (p20, p31, and a mixture of p20 and p31) respectively. After 7 d, both PPy/p20 and PPy/p31 promoted neuroectoderm formation from hESCs. After 14 d of culture, surfaces containing p20 showed the highest percentage of neuronal differentiation from hESC, while the PPy/p31 surface showed better cell attachment and spreading. In rNSCs cultures, a higher percentage of neurons were found on the PPy/p20 surface than other surfaces at 7 and 14 d. For differentiated neurons, p20 promoted both the primary and total neurite outgrowth. Longer primary neurites were found on p20-containing surfaces and a longer total neurite length was found on PPy/p20 surface. These results demonstrated that, by doping PPy with different bioactive peptides, differentiation of stem cells seeded at different stages of development is affected.     

In situ intercalative polymerization of conducting polypyrrole/montmorillonite nanocomposites

Conducting polypyrrole (PPy)‐montmorillonite (MMT) clay nanocomposites have been synthesized by the in situ intercalative polymerization method. The PPy‐MMT nanocomposites are characterized by field‐emission scanning electron microscopy (FE‐SEM), transmission electron microscopy (TEM), X‐ray diffraction (XRD), ultraviolet–visible (UV–vis) spectroscopy, thermogravimetric analysis (TGA), and Fourier‐transform infrared (FTIR) spectroscopy. XRD patterns show that after polymerization by the in situ intercalative method with ammonium persulfate and 1 M HCl, an increase in the basal spacing from 1.2 to 1.9 nm was observed, signifying that PPy is synthesized between the interlayer spaces of MMT. TEM and SEM micrographs suggest that the coexistence of intercalated MMT layers with the PPy macromolecules. FTIR reveals that there might be possible interfacial interactions present between the MMT clay and PPy matrix. The study also shows that the introduction of MMT clay results in thermal stability improvement of the PPy. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2279–2285, 2008     

Synthesis and in situ doping of highly conductive polypyrrole nanocomplexes with binary acids

The synthesis of doped polypyrrole (PPy) nanocomplexes and their size, morphology, doping level, and electrical conductivity are discussed. The synthetic route of doped PPy nanocomplexes is presented by means of the chemical oxidative polymerization and in situ doping process in the presence of a binary acid mixture (hydrochloric acid and perchloric acid). The electrical conductivities of the doped PPy nanocomplexes are enhanced from 0.88 to 4.5 S/cm by the optimum molar ratio of HClO₄ and HCl in the binary acid mixture. In addition, the average particle size of the doped PPy nanocomplexes decreases from 280 to 30 nm with a narrow particle size distribution when increasing the proportion of HClO₄ relative to HCl in the binary acid mixture; this result is confirmed by scanning electron microscopy, transmission electron microscopy, and capillary hydrodynamic fractionation instrument analyses. Moreover, at different molar ratios in the binary acid mixture, the zeta‐potential and oxidation level of the doped PPy nanocomplexes have a confirmed association with particle size and electrical properties. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 2329–2336     

In situ polymerization and morphology of polypyrrole obtained in water‐soluble polymer templates

Several water‐soluble polymers were used as templates for the in situ polymerization of pyrrole to determine their effect on the generation of nanosized polypyrrole (PPy) particles. The polymers used include: polyvinyl alcohol (PVA), polyethylene oxide (PEO), poly(vinyl butyral), polystyrene sulfonic acid, poly(ethylene‐alt‐maleic anhydride) (PEMA), poly(octadecene‐alt‐maleic anhydride), poly(N‐vinyl pyrrolidone), poly(vinyl butyral‐co‐vinyl alcohol‐co‐vinyl acetate), poly(N‐isopropyl acrylamide), poly(ethylene oxide‐block‐propylene oxide), hydroxypropyl methyl cellulose, and guar gum. The oxidative polymerization of pyrrole was carried out with FeCl₃ as an oxidant. The morphology of PPy particles obtained after drying the resulting aqueous dispersions was examined by optical microscopy, and selected samples were further analyzed via atomic force microscopy. Among the template polymers, PVA was the most efficient in generating stable dispersions of PPy nanospheres in water, followed by PEO and PEMA. The average size of PPy nanospheres was in the range of 160 nm and found to depend on the molecular weight and concentration of PVA. Model reactions and kinetics of the polymerization reaction of pyrrole in PVA were carried out by hydrogen ¹H NMR spectroscopy using ammonium persulfate as an oxidant. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Conducting Polypyrrole Conical Nanocontainers: Formation Mechanism and Voltage Switchable Property

Nanostructures with stimuli‐responsive properties are of great importance for the application of smart materials in nanotechnology. Unique hollow polypyrrole nanostructured arrays with a conical shape have been produced by a stepwise electropolymerization process. The polypyrrole conical nanocontainers exhibit a reversible switchable behavior between open and closed states, which is controlled by the movement of counter ions during electrically controlled reversible oxidation and reduction processes. The formation of conical nanocontainers is affected by the oleo‐wettability of the substrate. Conical nanocontainers can be formed on oleo‐phobic substrates in aqueous solution by using dopant‐stabilized pyrrole nanodroplets as the guiding template for the polymerization.

     

Surfactant-directed polypyrrole/CNT nanocables: synthesis, characterization, and enhanced electrical properties.

We describe here a new approach to the synthesis of size-controllable polypyrrole/carbon nanotube (CNT) nanocables by in situ chemical oxidative polymerization directed by the cationic surfactant cetyltrimethylammonium bromide (CTAB) or the nonionic surfactant polyethylene glycol mono-p-nonylphenyl ether (Opi-10). When carbon nanotubes are dispersed in a solution containing a certain concentration of CTAB or Opi-10, the surfactant molecules are adsorbed and arranged regularly on the CNT surfaces. On addition of pyrrole, some of the monomer is adsorbed at the surface of CNTs and/or wedged between the arranged CTAB or Opi-10 molecules. When ammonium persulfate (APS) is added, pyrrole is polymerized in situ at the surfaces of the CNTs (core layer) and ultimately forms the outer shell of the nanocables. Such polypyrrole/CNT nanocables show enhanced electrical properties; a negative temperature coefficient of resistance at 77-300 K and a negative magnetoresistance at 10-200 K were observed.     

Cellular adhesion, proliferation and viability on conducting polymer substrates

This work reports a comprehensive study about cell adhesion and proliferation on the surface of different electroactive substrates formed by pi-conjugated polymers. Biological assays were performed considering four different cellular lines: two epithelial and two fibroblasts. On the other hand, the electroactivity of the three conducting systems was determined in physiological conditions. Results indicate that the three substrates behave as a cellular matrix, even though compatibility with cells is larger for PPy and the 3-layered system. Furthermore, the three polymeric systems are electro-compatible with the cellular monolayers.     

Synthesis and characterization of polypyrrole dispersions prepared with different dopants

Stable polypyrrole dispersions were prepared by chemical oxidative polymerization of pyrrole in an aqueous medium containing different anionic salts - sodium benzoate, potassium hydrogen phthalate and sodium hydrogen succinate. Results of the elemental analysis and FT-IR spectroscopy confirmed that the anionic salts are incorporated in the conducting polymers and functioned as the dopants. The retardation of pyrrole polymerization was observed when a certain amount of the salt was used as dopant. SEM images of polypyrrole dispersions indicate large spherical particles (150-180nm). The conductivity of polypyrrole composites has also been investigated.     

Conductance and capacitance–frequency characteristics of polypyrrole/p‐type silicon structures

We formed a polypyrrole/p‐type silicon device by an anodization process. An aluminum electrode was used as an ohmic contact. From the current–voltage characteristics of the device, barrier height and ideality factor values of 0.662 eV and 1.734, respectively, were obtained from a forward‐bias current–voltage plot. Low capacitance–frequency and conductance–frequency measurements from 0.00 to 0.30 V with steps of 0.02 V were made. At each frequency, the measured capacitance decreased with increasing frequency because of a continuous distribution of the interface states in the frequency range of 5.0 Hz to 2.0 MHz. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1334–1338, 2003     

Conductivity of oriented bis-azo polymer films.

The conductivity properties of electro-optic, photoaddressable, dense bis-azo chromophore polymer films are investigated by using samples corona poled at various temperatures. A dielectric spectrometer is applied to measure the frequency dependence of the conductivity at different temperatures before and after heating the material to above the glass transition temperature. The results show that the orientation of the chromophores changes the charge-carrier mobility. Ionic conductivity dominates in a more disordered configuration of the material, while the competing process of hole hopping takes over as a transition to a liquid-crystalline phase occurs when the material is heated to much higher than the glass transition temperature. Such microcrystallization strongly enhances the conductivity.     

A Solution‐processible,n‐dopable polypyrrole derivative

In this study, soluble, n‐dopable, florescent, electrochromic polypyrrole derivative was synthesized through both chemical and electrochemical polymerization of 2‐[6‐(1H‐pyrrol‐1‐yl)hexyl]‐1H‐benzo[de]isoquinoline‐1,3(2H)‐dione (PyNI). The polymer synthesized through chemical polymerization had PL emission maxima at 471 and 543 nm and exhibited two redox couples at E_1/2,p = ?1.48 V and E_1/2,p = 1.12 V due to n‐type and p‐type doping, respectively. Electrochromic properties of electrochemically synthesized poly(PyNI) (PPyNI) were investigated via spectroelectrochemistry, kinetic studies, coloration efficiency, and colorimetry measurements. The optical band gap of PPyNI was calculated as 2.99 and 2.37 eV. Spectroelectrochemistry analysis of PPyNI reflected electronic transitions at 330–418 nm and 704 nm due to π–π* transition and charge carrier band formation, respectively. The polymer exhibited a switching time of 1.63 s and an optical contrast of 33.37%. Furthermore, dual‐type, complementary‐colored polymer electrochromic device in ITO/PPyNI/PEDOT/ITO configuration was assembled and characterized. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Carbon papers with conductive polymer coatings for use in solid-state supercapacitors

Conductive polymer-coated carbon papers have been fabricated through polymerisation of pyrrole-based monomers oxidised with various heteropolyacids. Smooth surfaces are obtained when multiple coatings are applied to the carbon surface and give good contact with the Nafion^® electrolyte. Cyclic voltammetry was used to study the electrodes and a.c. impedance and charge / discharge cycling was used to study membrane electrode assemblies (MEA). MEAs were fabricated using a hot-press technique.     

Polypyrrole electrodeposition on inorganic semiconductors CuInSe2 and CuInS2 for photovoltaic applications

Thin polypyrrole (PPy) layers with an average thickness of about 0.5 μm were deposited, using potentiostatic and galvanostatic techniques, on CuInSe₂ (CISe) structures prepared electrochemically on glass/ITO substrates and on CuInS₂ (CIS) structures fabricated on Cu tape substrates. The polymer layer of p-type is considered as an alternative to the traditional buffer layer and window layer in the conventional cell structure. The deposition proceeded from an aqueous solution containing sodium naphthalene-2-sulfonate as a dopant. In order to prepare stable PPy films of high quality with a good adherence to the surface of inorganic semiconductors CIS and CISe, the optimal concentrations of reagents, current densities and electrodepositing potentials were selected experimentally. Electrochemical polymerization of pyrrole to PPy on CIS surfaces is faster under white light irradiation and the polymerisation starts at lower potential than in the dark. Significant photovoltage and photocurrent of the fabricated CISe/PPy and CIS/PPy structures have been observed under standard white light illumination.     

High‐Conductivity Two‐Dimensional Polyaniline Nanosheets Developed on Ice Surfaces

A new method to develop two‐dimensional PANI nanosheets using ice as a removable hard template is presented. Distinctly high current flows of 5.5 mA at 1 V and a high electrical conductivity of 35 S cm^?1 were obtained for the polyaniline (PANI) nanosheets, which marked a significant improvement from previously values on other PANIs reported over the past decades. These improved electrical properties of ice‐templated PANI nanosheets were attributed to the long‐range ordered edge‐on π‐stacking of the quinoid ring, ascribed to the ice surface‐assisted vertical growth of PANI. The unprecedented advantages of the ice‐templated PANI nanosheets are two‐fold. First, the PANI nanosheet can be easily transferred onto various types of substrates via float‐off from the ice surfaces. Second, PANI can be patterned into any shape using predetermined masks, and this is expected to facilitate the eventual convenient and inexpensive application of conducting polymers in versatile electronic device forms.     

Solution route to inorganic nanobelt‐conducting organic polymer core‐shell nanocomposites

A facile and versatile solution‐based approach was developed to prepare semiconductor metal oxide nanobelt‐conducting organic polymer core‐shell nanocomposites. Well‐defined nanobelts of several types of oxide nanobelts were combined with conducting polymer [polypyrrole (PPy) and polyaniline (PANi)] via in situ polymerization in aqueous solution to obtain a new type of inorganic–organic composite nanostructure. Samples were characterized by using X‐ray diffraction, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared, electron energy loss spectra, high‐resolution transmission electron microscopy, and ultraviolet–visible techniques. Electron energy loss spectra revealed the existence of C?C and C? N bonds in coating layers to prove the encapsulation of PPy or PANi. The red‐shift of absorption band at high‐energy was observed for PPy‐encapsulated composites via ultraviolet–visible spectroscopy, and significant absorption band shifts were also encountered to PANi‐encapsulated composites, which suggest possibilities of band‐gap tuning of such metal oxide‐conducting polymer composites to be applied especially in solar cell devices. However, the sacrifice of nanobelts‐core led to hollow structures of PPy and PANi, which expands the synthetic strategies to prepare conducting polymer nanotubes. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2892–2900, 2005