Dopant effect and characterization of polypyrrole-cellulose composites prepared by in situ polymerization process

Polypyrrole (PPy)-cellulose composites were prepared by in situ polymerization of pyrrole in pulp suspension using ferric chloride as an oxidant. Some sulfonic compounds including p-toluenesulfonic acid and its sodium salt (PTSA and PTSA-Na), benzenesulfonic acid (BSA), dodecylbenzene sulfonic acid and its sodium salt (DBSA and DBSA-Na), 2-naphthalene sulfonic acid (NSA) and 9,10-anthraquinone-2-sulfonic acid sodium salt (AQSA-Na) were used as dopants, and their effect on the conductivity of PPy-cellulose composite was investigated. The results showed that the species and dose of dopants had significant effect on the surface resistivity and environmental stability of PPy-cellulose composite. As the dopant, PTSA and DBSA had a superior doping effect compared to their sodium salts. The doping result of BSA was close to that of PTSA. NSA bearing a naphthalene ring and AQSA-Na bearing an anthraquinone ring gave the best conductivity. Using NSA or AQSA-Na as a dopant, along with suitable polymerization conditions, the PPy-cellulose composite obtained showed a surface resistivity as low as 20 Ω cm⁻². For most dopants, the lowest surface resistivity could be obtained when the molar ratio of dopant to pyrrole was 1:1. Both ATR-FTIR (attenuated total reflection-Fourier transform infrared spectroscopy) and XPS (X-ray photoelectron spectroscopy) analysis confirmed that the PPy on pulp fibers doped with PTSA, PTSA-Na, NSA and AQSA-Na had different doping levels. The higher doping level of the PPy in the composites doped with NAS and AQSA-Na might be related to the stronger interaction of cellulose with PPy chains. Both SEM (scanning electron microscopy) and AFM (atomic force microscopy) observation revealed the fine grain microstructure of the PPy on the composites with average grain sizes in the range of 100–200 nm, and the PPy on the samples doped with NSA and AQSA-Na exhibited quite different morphology as compared to those doped with PTSA and its sodium salt.     

Preparation of Polypyrrole/Poly(methyl methacrylate) Core-Shell Nanoparticles in Four-Component Microemulsion Media

Electrically conductive polypyrrole (PPy)/poly(methyl methacrylate) (PMMA) core-shell nanoparticles were synthesized by two-step microemulsion polymerization. PPy core particles were prepared in a four-component microemulsion system, which was formed with surfactant cetyltrimethyl ammonium bromide (CTAB), cosurfactant n-pentanol, water, and pyrrole. Ferric chloride and iodine was added as the oxidant and the dopant, respectively. Then the PPy nanoparticles were coated with PMMA to prepare PPy/PMMA core-shell nanoparticles. The morphology of PPy/PMMA core-shell nanoparticles was characterized with transmission electron microscopy (TEM). Fourier transform infrared (FTIR) spectroscopy was used to characterize the structure of the samples. The electrical conductivities of samples were studied by a Hall effect testing instrument. Despite being coated with a layer of insulation, the conductivity of the composite PPy/PMMA core-shell nanoparticles could still reached to 7.856 × 10^?1 S/cm.     

Synthesis and characterisation of sterically stabilised polypyrrole particles using a chemically reactive poly(vinyl amine)-based stabiliser

Poly(vinyl amine) (PVAm) was derivatised using 2-thiophenecarboxaldehyde via Michael addition to prepare a statistical copolymer stabiliser for the synthesis of primary amine-functionalised polypyrrole (PPy) particles. A minimum stabiliser concentration of around 20 % (w/v) relative to pyrrole was required for well-defined PPy particles of approximately 100–200 nm, as judged by transmission electron microscopy (TEM) and dynamic light scattering (DLS). FTIR spectroscopy confirmed that stabiliser grafting had occurred, while x-ray photoelectron spectroscopy (XPS) studies indicated a stabiliser surface coverage on the PPy particles of around 53 %. PPy particles prepared at stabiliser concentrations below 20 % (w/v) were not colloidally stable above pH 6. However, higher stabiliser concentrations (e.g., 50 % (w/v) based on pyrrole) led to a significant improvement, with colloidal stability being retained above pH 7. Long-term colloidal stability studies of PPy particles stored at pH 7.5 confirmed that the amine-based stabiliser produced more stable aqueous dispersions than the imine-based stabiliser, since the latter bond is hydrolytically unstable.     

Synthesis of polypyrrole micro/nanofibers via a self-assembly process

Novel polypyrrole (PPy) micro/nanofibers were synthesized via a self-assembly process by using 4-hydroxy-3-[(4-sulfo-1-naphthalenyl) azo]-1-naphthalenesulfonic acid (Acid Red B) as dopant and ferric chloride (FeCl₃) as oxidant. Experimental conditions, including the concentration of the dopant, reaction temperature and stirring state have been investigated for their influences on the morphology of the synthesized PPy micro/nanofibers. The products were characterized by scanning electron microscopy, transmission electron microscopy and Fourier-transform infrared spectroscopy. The formation mechanism of micro/nanofibers was studied. It is believed that the micelles formed by the dopant and pyrrole monomer act as templates during the synthesis process. Two functions of aggregation and synthesis are proposed in the reaction system simultaneously, and the morphologies of micro/nanofibers are the co-operations of these two functions. The maximum conductivity value of the PPy micro/nanofibers was 8.56 S cm^?1     

聚ε-己内酯/聚吡咯电纺膜的制备与性能

以吡咯(Py)和聚ε-己内酯(PCL)为原料、氯仿为溶剂,并掺杂一定量的十二烷基硫酸钠制备电纺膜,利用三氯化铁的氧化作用原位生成聚吡咯(PPy).对所得到的PCL/PPy电纺膜用红外光谱进行表征,在扫描电镜和透射电镜下观察纤维形貌,并测定力学性能和体积电阻率.结果表明,所生成的PPy以纳米粒子形式附着在电纺纤维表面,随着Py相对于PCL的质量百分含量由0增加到20%,PCL/PPy电纺膜的纤维直径从(730±341)nm逐渐下降至(325±84)nm;膜的拉伸模量和拉伸强度由不含Py的(25.7±0.8)MPa和(2.48±0.14)MPa分别增加至含有20%Py的(48.4±7.6)MPa和(5.05±0.59)MPa,断裂伸长率由(129±27)%下降至(86.2±9.1)%;体积电阻率降低了2～3个数量级.该PCL/PPy电纺纤维膜以期可作为电活性材料用于功能或生物医用领域.     

聚吡咯/多壁碳纳米管及其聚氨酯导电复合材料的制备和性能

以羧基化多壁碳纳米管(MWCNTs)做模版剂,采用化学氧化法将吡咯(Py)在羧基化MWCNTs表面聚合制备PPy/MWCNTs导电材料,将其添加到溶剂型聚氨酯(PU)溶液中制备了PPy/MWCNTs/PU导电复合材料,研究了Py用量对PPy/MWCNTs及其PU复合材料性能的影响.研究表明,随Py用量的增加,PPy/MWCNTs的长度不变,管径增大,sp~2和sp~3杂化C含量先提高后减少,N的掺杂梯度降低,PPy/MWCNTs的导电率高于羧基化MWCNTs和PPy.当Py用量为羧基化MWCNTs的20%时,其导电率最大.PPy/MWCNTs中N元素的掺杂程度及其管径变化是引起PPy/MWCNTs/PU复合材料的性能不同的主要原因.增加Py用量,MWCNTs中亲水的羧基因对PPy掺杂而消耗,相同导电材料用量时纳米导电粒子数目相对减少,PPy/MWCNTs/PU复合材料的耐水性能提高,定向应力、储能模量和玻璃化温度降低,导电率先增加后减小.当Py用量为羧基化MWCNTs的15%时,导电率最大.     

Evaluation of the Conductivity of the Polypyrrole Film via Its CC Bonds Stretching on Surface‐Enhanced Raman Spectrum

In this study, the conductivities of various polypyrrole (PPy) films were evaluated via the corresponding surface‐enhanced Raman scattering (SERS) spectrum and X‐ray photoelectron spectroscopy (XPS). The results indicate that the peak position of C?C bonds stretching of PPy obtained from the SERS spectrum shows more exactly both qualitatively and quantitatively representing the conductivity of PPy than the N⁺/N ratio or the doping level obtained from the XPS analysis does. Namely the peak position of C?C bonds stretching of PPy monotone decreases to a lower frequency side with the increase of the conductivity of PPy. Furthermore, a satisfactory correlated equation between them was obtained. On the contrary, neither the N⁺/N ratio nor the doping level can be qualitatively reflective on the corresponding conductivity of PPy.     

Electrochemically Controlled Ion‐exchange Property of Carbon Nanotubes/Polypyrrole Nanocomposite in Various Electrolyte Solutions

The electrochemically controlled ion‐exchange properties of multi‐wall carbon nanotube (MWNT)/electronically conductive polypyrrole (PPy) polymer composite in the various electrolyte solutions have been investigated. The ion‐exchange behavior, rate and capacity of the electrochemically deposited polypyrrole with and without carbon nanotube (CNT) were compared and characterized using cyclic voltammetry (CV), chronoamperometry (CA), electrochemical quartz crystal microbalance (EQCM), X‐ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). It has been found that the presence of carbon nanotube backbone resulted in improvement in ion‐exchange rate, stability of polypyrrole, and higher anion loading capacity per PPy due to higher surface area, electronic conductivity, porous structure of thin film, and thinner film thickness providing shorter diffusion path. Chronoamperometric studies show that electrically switched anion exchange could be completed more than 10 times faster than pure PPy thin film. The anion selectivity of CNT/PPy film is demonstrated using X‐ray photoelectron spectroscopy (XPS).     

Facilely prepared polypyrrole-graphene oxide-sodium dodecylbenzene sulfonate nanocomposites by in situ emulsion polymerization for high-performance supercapacitor electrodes

The layered polypyrrole-graphene oxide-sodium dodecylbenzene sulfonate (PPyGO-SDBS) nanocomposites were facilely fabricated via an in situ emulsion polymerization method with the assistance of SDBS as dopant and stabilizer. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and electrochemical performance were employed to analyze the structure and the characteristics of the composites. The results showed that SDBS played an important role in improving the electrochemical performance of the PPyGO-SDBS, by dispersing the PPy between the layers of the GO. The obtained PPyGO-SDBS exhibited remarkable performance as an electrode material for supercapacitors, with a specific capacitance as high as 483 F g^?1 at a current density of 0.2 A g^?1 when the mass ratio of pyrrole to GO was 80:20. The attenuation of the specific capacitance was less than 20 % after 1,000 charge–discharge processes, supporting the idea that PPy inserted successfully into the GO interlayers. The excellent electrochemical performance seemed to arise from the synergistic effect between the PPy and the GO and the dispersion of the PPy induced by SDBS.     

Effect of ZnO nanoparticles doping on structural,dielectric and interfacial behavior of polyoxyethylene (20) sorbitan/ethylene glycol lyotropic phases

ABSTRACT

We are reporting on the interaction of zinc oxide (ZnO) nanoparticles (NPs) with the lyotropic phase comprises of Polyoxyethylene (20) sorbitan monolaurate and protic solvent ethylene glycol. The concentration of the NPs has been varying from 0.05 to 0.5 wt%. Multiwall lamellar and inverse phases have been observed at lower and higher concentration of ZnO NPs doping. Interestingly, the organization of ZnO NPs on the periphery and inside the periphery of ring-like structures has been observed at lower and higher concentration of the dopant, respectively. Such organization of the NPs can be explained considering interfacial interaction amid host and dopant and may also attribute to the adsorption mechanisms of surfactant. Effects of NPs doping on the dielectric dynamics has also been examined. About 32.6% decrease in the dielectric permittivity has been noticed at higher NPs doping. Such decrement in permittivity could be a result of the screening of the ZnO NPs dipole moment by the adsorption of surfactant molecules on their surface. Relaxation and optical parameters of the non-doped and doped mixtures have also been discussed.     

Effect of CdSe quantum dots doping on the switching time,localised electric field and dielectric parameters of ferroelectric liquid crystal

A systematic study highlighting the effect of cadmium selenide quantum dots (CdSe QDs) with varying concentrations of 0.05, 0.10 and 1.0 wt% doping on the electrooptical and dielectric parameters of ferroelectric liquid crystal (FLC) is presented. No considerable change is observed in phase transition temperature and tilt angle with CdSe QDs doping at lower and higher dopant level. Substantial enhancement of localised electric field at higher doping level (1.0 wt%) of CdSe QDs manifested the ≈48% reduction in the switching response of FLC nanocolloids at 30°C. Reduction in the spontaneous polarisation, dielectric constant and absorption strength could be attributed to the antiparallel correlation among dopant and matrix molecules, ion capturing in the capping additive layer and enhancement of the rotational viscosity of the nanocolloids, respectively. Goldstone mode relaxation frequency is found to be decreased with doping up to 0.10 wt% concentration and showed reverse effect at higher QDs concentration. QDs doping effect on the photoluminescence intensity is also discussed.     

Polymerization and characterization of high conductivity and good adhension polypyrrole films for electromagnetic interference shielding

<正>Polypyrrole(PPy) shows a favorable application in the electromagnetic interference(EMI) shielding due to its good electrical conductivity and outstanding air stability.Conducting PPy films with high conductivity and good adhesion were successfully polymerized on the surface of insulating epoxy resin substrates using chemical polymerization.The factors affecting the properties of PPy films,such as the surface morphology,adhesion between PPy film and substrate,electrical conductivity,EMI shielding effectiveness(SE),were investigated.The adhesion was improved significantly through a three-step surface pretreatment of epoxy resin substrates including removing impurities,roughening,and surface modification with silane coupling agent.An enhancement in the conductivity of PPy films of about one order of magnitude was achieved by adding dopant in FeCl_3 solution.The higher the conductivity,the better the shielding effectiveness.Taking sodium p-toluenesulfonate doped PPy film as example,EMI SE was in the practically useful range of about 30 dB over a wide frequency range from 30 MHz to 1500 MHz.The PPy film samples were characterized by scanning electron microscopy (SEM),infrared spectra(IR),X-ray photoelectron spectroscopy(XPS) and the flange coaxial transmission device.The fourpoint probe method was used to measure conductivity of PPy films.     

The effect of surface modification with nitric acid on the mechanical and tribological properties of carbon fiber‐reinforced thermoplastic polyimide composite

Polyacrylamideacrylate (PAN)‐based carbon fibers were submitted to nitric acid oxidation treatments to improve the interfacial adhesion of the carbon fiber (CF)‐reinforced polyimide (CF/PI) composite. The carbon fiber surfaces were characterized by X‐ray photoelectron spectroscopy (XPS). Nitric acid oxidation not only affects the oxygen concentration but also produces an appreciable change in the nature of the chemical functions, namely the conversion of hydroxy‐type oxygen into carboxyl functions. Nitric acid oxidation treatment modifies the element constituting the fiber, the nitrogen concentration being about 1.2 times higher at the fiber external surface compared to the untreated one. The mechanical and tribological properties of the polymide (PI) composites reinforced by the carbon fibers treated with nitric acid oxidation were investigated. Results showed that the tensile strength of the CF/PI composites improved remarkably due to nitric acid treatment along with enhancement in friction and wear performance. Copyright © 2009 John Wiley & Sons, Ltd.     

Sterically stabilized polypyrrole–palladium nanocomposite particles synthesized by aqueous chemical oxidative dispersion polymerization

Aqueous chemical oxidative dispersion polymerizations of pyrrole using PdCl₂ oxidant were conducted using water-soluble polymeric colloidal stabilizers in order to synthesize polypyrrole–palladium (PPy–Pd) nanocomposite particles in one step. PPy–Pd nanocomposite particles with number average diameters of approximately 30 nm were successfully obtained as colloidally stable aqueous dispersions, which were stable at least for 7 months, using poly(4-lithium styrene sulfonic acid) colloidal stabilizer. The resulting nanocomposite particles were extensively characterized with respect to particle size, size distribution, colloidal stability, nanomorphology, surface/bulk chemical compositions, and conductivity. X-ray photoelectron spectroscopy indicated the existence of poly(styrene sulfonic acid) colloidal stabilizer on the surface of the nanocomposite particles. Transmission electron microscopy studies confirmed that nanometer-sized Pd nanoparticles were distributed in the PPy matrix.     

Synthesis of electrically conductive polypyrrole-polystyrene composites using supercritical carbon dioxide: II. Effects of the doping conditions

A polymer composite of polypyrrole (PPy) and polystyrene (PS) was synthesized in this study. Pyrrole was firstly impregnated within the PS substrate where supercritical carbon dioxide (SCCO₂) at 40 °C and 10.5 MPa was used as the solvent. The resulting polymer composite was then soaked in a solution of metallic salt to form an electrically conductive product. Thermal analyses were carried out in this study. Glass transition temperatures from the DSC curves and thermal decomposition temperatures from the TGA curves were observed. These temperatures rise gradually from pure PS, undoped blend to doped composite that indicates blending took place in SCCO₂, and polymerization was proceeding when the pyrrole/PS blend was soaking in the doping solution. Furthermore, various effects of the doping conditions on the conductivity of the PPy/PS composite were investigated. Water and acetonitrile were used as the solvents where the former yielded a higher conductivity of the product. Various doping temperatures were studied and a maximum conductivity was observed at 25 °C. The conductivity also depends on the nature of the oxidant. A bell-shaped profile of the conductivity with respect to the concentration of each oxidant was obtained. The maximum conductivity of the composites with iron compounds as oxidants decreases in the following order of anions: chloride > sulfate > perchloride > nitrate in aqueous solutions. Comparison of the scanning electron microscope results of the composite was presented where chloride and nitrate anions were used as the oxidant. It was found that the composite with higher conductivity has higher bulk density and less porous morphology.     

Organic–inorganic polypyrrole‐surface modified SiO2 hybrid nanocomposites: a facile and green synthetic approach

Organic–inorganic hybrid nanocomposites composed of conductive polypyrrole (PPy) and surface modified silica (SiO₂) were successfully prepared through an in situ chemical oxidative polymerization in supercritical carbon dioxide (scCO₂). SiO₂ nanoparticles were surface modified using 3‐methacryloxypropyltrimethoxysilane (MPTMS) in order to disperse well in the medium. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) showed that the SiO₂ nanoparticles were encapsulated into the polymer. UV‐visible spectra of the diluted colloidal dispersions of PPy/SiO₂ hybrid nanocomposites were similar to those of PPy system. Fourier transform infrared spectroscopy (FT‐IR) suggested the strong interaction between PPy and SiO₂. Surface characterizations of nanocomposites were described by X‐ray photoelectron spectroscopy (XPS). The nanocomposites synthesized in scCO₂ have been shown to possess higher electrical conductivity and thermal stability. Copyright © 2009 John Wiley & Sons, Ltd.     

Comparison of surface and bulk doping levels in chemical polypyrroles of low,medium and high conductivity

Chemical polypyrroles (PPys) of low (σ < 75 S/cm), medium (75 < σ < 200 S/cm) and high electrical conductivity (σ > 200 S/cm) having chloride dopants have been investigated by XPS, chloride ion‐selective electrode (ISE) measurements and high‐resolution termogravimetric analysis (TGA). The average surface doping level in these PPys was 0.28 ± 0.03 as determined from deconvoluted XPS N 1s, Cl 2p and C 1s spectra by using the well‐established N⁺/N and Cl^?/N atomic ratios as well as a new ratio denoted as Cα*/Cα_Total. This new ratio provides an estimation of the relative amount of α‐C atoms in charged pyrrole units per total α‐C atoms. The average bulk doping level in these materials was 0.31 ± 0.02 from direct chloride ISE measurements. High‐resolution TGA was employed for the first time in the determination of the amount of hydrogen chloride evolved from the PPy samples during degradation at high temperatures. The resulting average bulk doping level by TGA was 0.30 ± 0.04 for these PPys, in very good agreement with the ISE results. Since surface and bulk doping levels are almost identical for the PPys of low, medium and high conductivity, the differences in conductivity between samples have been attributed to differences in conjugation length among them. For PPy of high conductivity (σ = 288 S/cm), a conjugation length 2.6 times higher than that of PPy of low conductivity (σ = 29 S/cm) has been calculated. Copyright © 2006 John Wiley & Sons, Ltd.     

Carboxy-endcapped conductive polypyrrole: biomimetic conducting polymer for cell scaffolds and electrodes

Numerous regenerating tissues respond favorably to electrical stimulation, creating a need for a bioactive conducting platform for tissue engineering applications. The drive for biosensors and electrode coatings further requires control of the surface properties of promising conductive materials such as polypyrrole. Here we present carboxy-endcapped polypyrrole (PPy-alpha-COOH), a unique bioactive conducting polymer with a carboxylic acid layer, composed of a polypyrrole (PPy) surface modified with pyrrole-alpha-carboxylic acid (Py-alpha-COOH). This unique structure is simple to produce, provides a stable bioactive surface via covalent bonds, and preserves bulk properties such as electrical conductivity and mechanical integrity. The chemical structure of this polymer composite was characterized by angle-resolved X-ray photoelectron spectroscopy (XPS), which demonstrated the presence of carboxylic acid functionality on the top surface of conductive PPy. A four-point probe test was used to verify the similar conductivity of PPy-alpha-COOH compared to that of standard PPy. To demonstrate the potential to influence cellular activity, the carboxylic acid monolayer surface was grafted with the cell-adhesive Arg-Gly-Asp (RGD) motif. Human umbilical vein endothelial cells (HUVECs) cultured on RGD-modified PPy-alpha-COOH demonstrated significantly higher adhesion and spreading than on the negative controls PPy-alpha-COOH and unmodified PPy.     

染料掺杂聚吡咯微纳米管的合成及其影响因素研究

以水溶性染料酸性红G为掺杂剂, 以三氯化铁为氧化剂, 采用无模板自组装方法制备得到了聚吡咯微/纳米管. 利用FTIR, XRD, SEM, TEM对所合成的聚吡咯微/纳米管的结构形貌进行了表征. 结果表明, 搅拌条件下, 酸性红G原位掺杂得到的聚吡咯管直径在100～910 nm之间, 管长大于50 μm. XRD表明所得聚吡咯微/纳米管为无定形态. 研究了反应时间、反应温度、吡咯浓度、掺杂剂与吡咯浓度比、氧化剂滴加速度等对聚吡咯管形貌的影响, 获得了最佳的反应条件.     

Optical,electrical, and electrochemical behavior of p-type nanostructured SnO<Subscript>2</Subscript>:Ni (NTO) thin films

The physical and electrochemical properties of sol-gel synthesized nickel-doped tin oxide (NTO) thin films were investigated. The X-ray diffraction results showed that NTO samples exhibited a tetragonal structure. The average crystallite size and the unit cell volume of the films were reduced by Ni increment, while the stacking fault probability was increased. Furthermore, the field-emission scanning electron microscopy images clearly displayed that the worm-like surface morphology of the SnO₂ thin films was altered to the spherical feature in 3 and 10 mol% NTO samples. Moreover, by virtue of Ni incorporation, the average transparency of the SnO₂ thin films rose up from 67 to 85% in the visible region; also, the optical band gap of the SnO₂ sample (3.97 eV) increased and the thin film with 3 mol% dopant concentration showed a maximum value of 4.22 eV. The blue/green emission intensities of photoluminescence spectra of SnO₂ thin film changed via Ni doping. The Hall effect measurements revealed that by Ni addition, the electrical conductivity of tin oxide thin films altered from n- to p-type and the carrier concentration of the films decreased due to the role of Ni²⁺ ions which act as electron acceptors in NTO films. In contrast, 20 mol% Ni-doped sample had the highest mobility about 9.65 cm² (V s)^?1. In addition, the cyclic voltammogram of NTO thin films in KOH electrolyte indicated the charge storage capacity and the surface total charge density of SnO₂ thin films enhanced via Ni doping. Moreover, the diffusion constant of the samples increased from 2?×?10^?15 to 6.5?×?10^?15 cm² s^?1 for undoped and 5 mol% dopant concentration. The electrochemical impedance spectroscopy of the NTO thin films in two different potentials showed the different electrochemical behaviors of n- and p-type thin films. It revealed that the 20 mol% NTO thin film had maximum charge transfer at lower applied potential.