Electrochemical polymerization of water-soluble and insoluble monomers in supercritical carbon dioxide-in-water emulsion

Dense carbon dioxide is an environmentally benign solvent, but its non-polarity limits the use of carbon dioxide as a reaction medium for electrochemical reactions. We have previously reported that the electrochemical polymerization in a carbon dioxide-in-water (C/W) emulsion proceeds to form conductive polypyrrole films [Jikei M, Saitoh S, Yasuda H, Itoh H, Sone M, Kakimoto M, et al. Polymer 2006;47:1547-54]. In this study, the effect of reaction conditions of the electrochemical polymerization on the resulting polypyrrole films was systematically investigated in order to reveal the features, flexibility and limitations of the C/W emulsion as a medium for electrochemical reactions. Other monomers, such as aniline and 3,4-ethylenedioxythiophene, were also examined for the electrochemical polymerization in the C/W emulsion. We have found that water-soluble monomers, such as pyrrole and aniline, are suitable for the electrochemical polymerization in the C/W emulsion that form films with a fine uneven texture.     

On the morphology and growth of electrochemically polymerized polypyrrole

Samples of polypyrrole p-toluene sulfonate have been prepared by electrochemical polymerization from aqueous and methanolic solutions. The morphology and molecular ordering have been studied by scanning and transmission electron microscopy, polarizing optical microscopy and wide-angle X-ray scattering. Specimens prepared from aqueous solution develop as compact films, which exhibit considerable molecular anisotrophy; cross-sections are highly birefringent and the local molecular orientation is found to correlate with the nodular surface features. Transmission electron microscopy also reveals evidence of supermolecular ordering within the films, which is consistent with the optical observations. Samples prepared from methanolic solutions appear very different: no evidence of molecular anisotropy or internal subdivision has been observed. These films are massively voided as a result of extensive internal delamination, which occurs after the polypyrrole is deposited onto the work electrode. On the basis of the observed morphologies, modes of growth are proposed, based upon polymerization in solution followed by a degree of further chain development after precipitation.     

分级多孔聚吡咯膜的界面自组装合成与电化学电容性

通过界面自组装聚合,在长链表面活性剂OP10的辅助下成功制备了分级多孔结构聚吡咯膜。对所得聚吡咯的分子结构、微观形貌和电化学性能分别进行了表征和研究。结果表明：界面聚合中引入OP10对聚吡咯的分子结构并没有影响,但对其微观形貌却具有重要作用。当OP10的用量优化为0.02 g时,聚吡咯可自组装形成分级多孔结构,既有纳米孔（约100 nm）,也有亚微米孔（200~1000 nm）和微米孔（1~3.5 μm）。由于相对较高的活性表面积和总孔体积,分级多孔聚吡咯作为电极材料最大比电容可达357 F·g^-1,比相同条件下传统界面法制备的聚吡咯高70%以上。此外,2000次充放电循环后该材料仍保持初始比电容的87.6%,表明其优异的循环稳定性。     

Preparation of poly(vinylidene fluoride)–polypyrrole composite films by electrochemical synthesis and their properties

Composite films of poly(vinylidenc fluoride–polypyrrole (PVDF–PPy) were prepared by electrochemical polymerization of pyrrole on a very thin PVDF matrix film (～ 0.5 μm). The polymerization was carried out in aqueous media using stainless steel, coated with PVDF matrix, as a working electrode, and p-toluene sulfonate (PTS), as a dopant. The films were prepared at different voltages for different durations of time in order to optimize the conditions of composite formation. The resulting films were characterized by studying IR spectra, conductivity, SEM, XRD, and tensile strength measurements. The mechanical properties of the composites were found to have improved, while the conductivity remained more or less same as that of pure PPy. © 1995 John Wiley & Sons, Inc.     

The morphology and conductivity of polypyrrole/polyurethane alloy films

Polymeric composites with conductivities ranging from 10^–4 to 1 S cm^–1 were prepared by electrochemically polymerizing pyrrole in a matrix of polyurethane. The polypyrrole/polyurethane alloy films obtained were characterized by element analysis, electron microscopy and electrical conductivity measurements. The morphology of the films depended on the solvent, the electrolyte and the current density. The mechanism of the electrochemical polymerization showed that PPy grew in a treelike structure, with molecular chains extending from the electrode surface into the solution. The transition temperature of the PPy/PU increased with the PPy content.     

Synthesis and characterization of emulsion polymerized mixed matrix aluminum silicate/poly(2,6‐dimethyl 1,4‐phenylene oxide) films

A series of poly (2,6‐dimethyl‐1,4‐phenylene oxide) (PPO)‐based organic/inorganic films for the potential application in membrane gas separation were prepared by employing a method in which aluminum hydroxonitrate contained in a stable water‐in‐oil (W/O) emulsion, the oil phase being a solution of PPO in trichloroethylene, was mixed with a homogeneous solution of PPO in trichloroethylene containing tetraethyl orthosilicate (TEOS). Inorganic polymerization occurred in or at the surface of the aqueous droplets of the W/O emulsion. Subsequently, thin films were prepared by a spin coating technique, and they were referred to as emulsion polymerized mixed matrix (EPMM) films. Scanning electron micrographs taken from a film cross section indicated the presence of particles in the PPO matrix, and energy dispersive X‐ray measurements showed that the embedded particles contained Al and Si elements. Differential scanning calorimetry analysis showed a decrease in the glass transition of the EPMM films with increase of TEOS loading. The compatibility between aluminum silicate nanoparticles and PPO in the EPMM films was confirmed by air separation tests. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Preparation of conducting polyacrylonitrile/polypyrrole composite films by electrochemical synthesis and their electrical properties

Electrically conducting polyacrylonitrile (PAN)/polypyrrole (PPy) composite films were prepared by electrochemical polymerization of pyrrole in an insulating PAN matrix under various polymerization conditions and their electrical properties were studied. The conductivities of PAN/PPy composite films peeled off from the platinum electrode he lie in the range of 10^?2–10^?3 s/cm, depending on the preparation conditions: The conductivity increased with the concentrations of the electrolyte and the monomer, but it decreased with the polymerization temperature of pyrrole and the applied potential.     

The processing and mechanical properties of polypyrrole/polyurethane alloy films

Polymeric composites of polypyrrole/polyurethane (PPy/PU) were prepared by electrochemical polymerization. The resulting films had conductivities ranging from 10^–4 to 1S cm^–1, and showed significant improvement in their mechanical properties. By varying the conditions of polymerization, a range of mechanical, as well as electrical, properties could be obtained.     

Electrosynthesis and capacitive performance of polyaniline–polypyrrole composite

The composite of polyaniline and polypyrrole (PPY‐PANI) was prepared by two‐step electrochemical polymerization method. Techniques of scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), and thermal gravity analysis (TG/DTG) measurements were used to characterize the morphology and structure of the composite. The electrochemical properties of the composite were investigated by cyclic voltammetry (CV), galvanostatic charge‐discharge, and electrochemical impedance spectroscopy (EIS). The results indicated that the polyaniline–polypyrrole composite showed better electrochemical capacitive performance than polypyrrole (PPY) and polyaniline (PANI). The specific capacitance of the composite electrode was 523 F/g at a current of 6 mA/cm² in 0.5 M H₂SO₄ electrolyte. POLYM. COMPOS., 2011. © 2010 Society of Plastics Engineers     

Thermo-sensitive poly(N-vinylcaprolactam-co-acetoacetoxyethyl methacrylate) microgels: 2. Incorporation of polypyrrole

In a previous paper [Polymer (2003) in press DOI: 10.1016/j.polymer.2003.09.037] polymeric temperature-sensitive microgels were prepared by surfactant-free emulsion co-polymerization of N-vinylcaprolactam (VCL) and acetoacetoxyethyl methacrylate (AAEM). In the present work, VCL/AAEM microgels were used as a template for oxidative polymerization of pyrrole (Py). It was found that pyrrole polymerization takes place directly in microgel structure leading to composite particles. Influence of microgel structure and amount of incorporated polypyrrole (PPy) on particle properties is discussed. Obtained stable composite microgels show similar thermal sensitivity as VCL/AAEM particles with fully reversible collapse-swelling properties.     

Study of the anticorrosive properties of polypyrrole/polyaniline bilayer via electrochemical techniques

In this work, using electrochemical techniques the authors investigated the protective properties of a polypyrrole/polyaniline bilayer as a conductive polymer. A polypyrrole/polyaniline bilayer was deposited on carbon steel substrate by potentiostatic method. The electric capacitance and resistance of the films were monitored with the immersion time in a corrosive solution to investigate the water permeability of the films. Polypyrrole/polyaniline bilayer has a relatively low permeability and good catalytic behavior in passivation of carbon steel in longer periods. The results show that the bilayer has a better anticorrosive behavior compared to homopolymers (polypyrrole and polyaniline).     

Preparation and characterization of an enzyme electrode based on cholesterol esterase and cholesterol oxidase immobilized onto conducting polypyrrole films

Cholesterol esterase (ChEt) and cholesterol oxidase (ChOx) enzymes were entrapped within polypyrrole (PPy) films on a platinum disc electrode during electrochemical polymerization. The characteristics of the PPy/ChEt/ChOx enzyme electrode thus prepared were investigated as a function of the time, pH, temperature, and concentration of cholesteryl palmitate by a spectrophotometric method. PPy/ChEt/ChOx electrodes can be used for the estimation of cholesteryl palmitate concentrations from 1 to 8 mM, can be used least 10 times, and have a shelf life of about 1 month at 4–10°C. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3769–3773, 2004     

聚偏氟乙烯-丙烯酸酯原位乳液聚合的研究

采用原位乳液聚合 ,将聚偏氟乙烯 (PVDF)溶解于丙烯酸酯单体中 ,以碳氟表面活性剂 (FC- 80 ,氟醚 )和碳氢表面活性剂 (SLS、OP - 10 )为乳化剂 ,合成了PVDF改性的聚丙烯酸酯乳液 ,乳液在六个月内无分层现象。并用偏光显微镜和示差量热扫描仪对涂膜的结晶行为和热行为进行了研究 ,结果表明 :聚丙烯酸酯破坏了聚偏氟乙烯的结晶性使得改性后的胶膜透明。     

Synergy effects between single-walled carbon nanotubes and polypyrrole on the electrocatalysis of their composites for the oxygen reduction reaction

To develop the high-efficiency carbon alloy catalysts with significant interaction of C–N, the synergy effects of the polypyrrole/single-walled carbon nanotube (PPy/SWCNT) composites have been studied for the oxygen reduction reaction (ORR) in an alkaline solution. The synergy effects between PPy and SWCNT have been found in the synthesized PPy/SWCNT composites by the characterization using FE-SEM, Raman spectroscopy, XRD, TGA, electrical conductivity, and the electrochemical measurements for the surface area and the electrochemical activities of sites: electron transfer rate, differential capacitance and chemisorbed H-stripping voltammetry. The synergy effects have significantly affected the electrochemical properties of the PPy/SWCNT composites and the electrocatalytic potential at the active sites. The PPy/SWCNT composites synthesized using the electrochemical polymerization method with an identified PPy:SWCNT weight ratio of 1:2 show the best performance of the ORR. For the electrode process on the PPy/SWCNT composites, a mixture of two-electron and four-electron processes occurred. It was found that the synergy effects in the PPy/SWCNT composite electrodes synthesized using the electrochemical polymerization method with a thin net-like PPy film were stronger than those using the chemical polymerization method with a thick shell-like PPy film and played an important role in the ORR electrode kinetics.     

Preparation of polypyrrole/ferrocyanide films modified carbon paste electrode and its application on the electrocatalytic determination of ascorbic acid

Functionalized polypyrrole film were prepared by incorporation of (Fe(CN)₆)⁴⁻ as doping anion, during the electropolymerization of pyrrole onto a carbon paste electrode (CPE) in aqueous solution by using potentiostatic method. The electrochemical behavior of the (Fe(CN)₆)³⁻/(Fe(CN)₆)⁴⁻ redox couple in polypyrrole was studied by cyclic voltammetry and double step potential chronoamperometry methods. In this study, an obvious surface redox reaction was observed and dependence of this reaction on the solution pH was illustrated. The electrocatalytic ability of polypyrrole/ferrocyanide films modified carbon paste electrode (Ppy/FCNMCPEs) was demonstrated by oxidation of ascorbic acid. It has been found that under optimum condition (pH 7.00), the oxidation of ascorbic acid at the surface of such electrode occurs at a potential about 540 mV less positive than unmodified carbon paste electrode. The kinetic parameters such as electron transfer coefficient, α and catalytic reaction rate constant, k_h′, were also determined by using various electrochemical approaches.The catalytic oxidation peak current showed a linear dependent on the ascorbic acid concentration and a linear calibration curve was obtained in the range of 4.5×10⁻⁴ to 9.62×10⁻³ M of ascorbic acid with a correlation coefficient of 0.9999. The detection limit (2σ) was determined as 5.82×10⁻⁵ M.     

Surface conducting particles by oxidative copolymerization of pyrrole pendant groups and pyrrole in emulsion

Summary Poly(styrene-co-(p-vinylbenzyl 4-(3-pyrrolyl)-4-oxobutyrate)) (PSt-VBPOB) containing 16.7 mol% of p-vinylbenzyl 4-(3-pyrrolyl)-4-oxobutyrate (VBPOB) was synthesized by emulsion polymerization. Pyrrole was coupled onto pyrrole moiety of PSt-VBPOB via oxidative polymerization using FeCl₃ as a catalyst. Two kinds of conducting polymers, PSt-VBPOB-ox-Py (S) and PSt-VBPOB-ox-Py (E), were prepared. PSt-VBPOB-ox-Py (S) was prepared in THF solution. On the other hand, PSt-VBPOB-ox-Py (E) was obtained in the emulsion. The conductivity of PSt-VBPOB-ox-Py (E) (1.590 S/cm) was much higher than that of PSt-VBPOB-ox-Py (S) (0.022 S/cm). The mechanisms of electrical conductivity enhancement in PSt-VBPOB-ox-Py (E) is proposed. In the PSt-VBPOB-ox-Py (S) particles, polypyrrole was uniformly distributed throughout the particles. On the other hand, polypyrrole links are mainly located on the surface of the PSt-VBPOB-ox-Py (E) particles, giving surface conducting particles.     

Polypyrrole electropolymerized on aluminum alloy 1100 doped with oxalate and tungstate anions

Polypyrrole films doped with oxalic acid and tungstate were potentiostatically electropolymerized on aluminum alloy 1100. Two statistical factorial designs (fractional and complete) were used to study the influence of the synthesis variables on the film performance against corrosion. Corrosion protection of the polypyrrole films doped with oxalate and tungstate anions (PPy/OXA/W) on the aluminum alloy was evaluated by potentiometric and electrochemical impedance spectroscopy (EIS) measurements in a 0.05 mol L⁻¹ NaCl solution. The results obtained showed that the best performance against corrosion was detected with the PPy/OXA/W film synthesized at 1.0 V, 1.5 C in 0.2 mol L⁻¹ pyrrole, 0.1 mol L⁻¹ oxalic acid and 0.05 mol L⁻¹ sodium tungstate solutions provide a protective effect against corrosion.     

The corrosion-inhibiting effect of polypyrrole films doped with p-toluene-sulfonate,benzene-sulfonate or dodecyl-sulfate anions,as coating on stainless steel in NaCl aqueous solutions

This article presents a study of the conditions for electro-synthesis of polypyrrole (PPy) films on stainless steel, in the presence of the anions p-toluene-sulfonate (pTS), benzene-sulfonate (BS) or dodecyl-sulfate (DS). Cyclic voltammetry (CV) was used in the synthesis of the polypyrrole films on the stainless steel (SS). These polymeric films were characterized by IR and UV–vis spectroscopy and their morphology and thickness were analyzed by scanning electron microscopy (SEM). Their performance as protective films against corrosive processes presented by the SS/PPy-pTS, SS/PPy-BS or SS/PPy-DS systems was evaluated in 0.1 M NaCl aqueous solution. The study of the corrosion processes of the stainless steel/polymer systems was conducted through measurements of open circuit potential (E_OCP), polarization curves (PC) and electrochemical impedance spectroscopy (EIS). The results showed that the protective capacity of these polymeric systems on stainless steel, mainly with regard to pitting, depends on the nature of the anion dopant used during electro-synthesis of the PPy film. The best performance was seen with the dopants pTS and BS.     

Cross-linking in polypyrrole and poly(N-methylpyrrole): Comparative experimental and theoretical studies

A comparative study about cross-linking in electrogenerated polypyrrole and poly(N-methylpyrrole) is presented. Experimental studies on polymer films prepared under a constant potential of 1.4 V but considering different polymerization times as well as quantum mechanical calculations on model oligomers indicated that cross-linking is very low in polypyrrole, while cross-links are frequently formed by poly(N-methylpyrrole) chains. These behaviors have been attributed to the architecture of the molecular chains, which is completely different for the two systems under study. Thus, polypyrrole forms linear chains with some irregularities in the inter-ring linkages, while branched molecules with many irregularities are the most stable for poly(N-methylpyrrole). These remarkable differences are fundamentally due to the steric repulsions induced by the methyl groups of poly(N-methylpyrrole).     

细乳液聚合制备改性硅溶胶／聚丙烯酸酯复合乳液

常温下一步法制备改性硅溶胶,并通过细乳液聚合制备改性硅溶胶／聚丙烯酸酯复合乳液。考查了温度对聚合速率和单体转化率的影响以及不同乳化剂含量下聚合过程中乳胶粒粒径的变化情况;测试了乳胶膜的吸水率,并用接触角法表征了乳胶膜的表面自由能。