Electrochemical polymerization of pyrrole in supercritical carbon dioxide-in-water emulsion

Supercritical carbon dioxide is an environmentally benign solvent but its low polarity limits electrochemical reactions in it. We now report the electrochemical polymerization of pyrrole in a supercritical carbon dioxide-in-water (C/W) emulsion in the presence of a surfactant. Black polypyrrole films were formed on Pt electrodes, whose conductivity was comparable with non-oriented polypyrrole prepared in conventional solvents. The structure of the polypyrrole films was confirmed by IR and Raman spectroscopic measurements. p-Toluenesulfonic acid was a suitable supporting electrolyte among the electrolytes examined for the electrochemical polymerization in the C/W emulsion. A typical nodular morphology was observed on the basis of the SEM and AFM measurements. Confocal scanning microscope revealed the formation of a fine uneven texture on the film prepared in the C/W emulsion.     

Interfacial polymerization of pyrrole and in situ synthesis of polypyrrole/silver nanocomposites

We present a new synthetic approach leading to the formation of polypyrrole architectures in submicron level and to silver/polypyrrole nanocomposites via an interfacial polymerization in a water/chloroform interface. The oxidizing agent was either Ag(I) or Fe(III). In the first case, silver nanoparticles resulted. The mean diameter of the polypyrrole structures is in the range of 200-300 nm according to the addition or not of various surfactants. The progress of the reaction was studied by UV-visible spectroscopy, which also revealed the formation of a polaron band during the growth of the oligomers. The crystal structure of the polymers was examined by X ray diffractometry and all samples appeared to be amorphous, while the samples were further characterized by thermogravimetric analysis and FT-IR spectroscopy.     

Polypyrrole micro- and nanowires synthesized by electrochemical polymerization of pyrrole in the aqueous solutions of pyrenesulfonic acid

Polypyrrole (PPy) micro- and nanowires were synthesized through electrochemical polymerization of pyrrole in the aqueous solutions of 1-pyrenesulfonic acid (PSA), in which PSA acted as both surfactant and dopant. Macroscopic studies (SEM and TEM) indicated that the PPy wires have diameters of 120-500 nm and length of several micrometers. Electrochemical investigation demonstrated that the PPy wires have much stronger electrochemical activity than the conventional flat PPy film because of their higher specific surface area. Furthermore, the PSA doped PPy wires showed strong emission in an aqueous dispersion. A possible micelle guided formation mechanism has been proposed and investigated.     

1-癸烯齐聚物的催化合成与反应动力学行为研究

以1-癸烯为原料,分别采用AlCl3/TiCl4和氯化铝催化体系进行了合成1-癸烯齐聚化合物的研究。研究结果表明两催化剂均可实现1-癸烯齐聚化合物的合成,但两者聚合度有差异,考虑后续处理和环境污染问题,宜采用AlCl3/TiCl4催化体系,并初步确定该反应体系最佳反应温度为40℃、反应时间为4h;齐聚反应动力学过程测试表明,随着齐聚反应的进行,CH2双键逐步减少同时伴随CH不断的生成和消耗,均呈现出同步下降趋势,表明齐聚反应过程中存在着α-烯烃的歧化反应,且歧化产物参与了齐聚反应;连续在线各官能团红外谱图分析反映出的可能反应过程与以最终反应产物的信息来推断反应过程研究文献报道基本吻合。     

Investigation of ethylene oxide oligomerization during functionalization of poly(butadienyl)lithium using MALDI-TOF MS and H NMR analyses

Oligomerization of ethylene oxide during the functionalization of poly(butadienyl)lithium in benzene and cyclohexane at 25 °C has been investigated by MALDI-TOF MS and ¹H NMR. Chemically significant amounts of oligomer were found using 4 equiv. of ethylene oxide ([EO]/[PLi]) after 12 h in both benzene and cyclohexane. No oligomer was observed when the reaction time was minimized.     

Electrically-assisted chemical vapor polymerization: A novel method for in situ polymerization of pyrrole

This article offers a fast and innovative process for carrying out in situ polymerization of pyrrole onto a polyester fabric. This process is based on electrically-assisted chemical vapor polymerization that takes around 180 s to produce an electroconductive fabric with a surface resistance of as low as 70 Ω. The ultrasonication carried out at 20 kHz frequency is quite effective in binding the polymer to the fabric. Fourier-transform infrared spectroscopy and X-ray diffraction studies confirm that the polymer formed is polypyrrole. The application of electric potential across an oxidant-enriched fabric results in polymer add-on of polypyrrole as high as 250%. The amount of polypyrrole formed and the surface resistance of the fabric are found to depend on the potential applied across the fabric. The concentrations of the oxidant and the dopant, the time of polymerization, and the rate of monomer vaporization are found to be critical in deciding the surface resistance of the fabric.     

Polypyrrole-carbon fiber composite film prepared by chemical oxidative polymerization of pyrrole

Polypyrrole-carbon fiber (Ppy-CF) composite films with carbon fiber (CF) content ranging from 15 to 20 wt % have been prepared by chemical oxidative polymerization of pyrrole at the surface of a CF-covered Teflon substrate following a layer-by-layer deposition approach. The composites have a high modulus of 8–9 × 10¹⁰ dyn/cm², high tensile strength of 200–270 kg/cm², and good thermal stability. More importantly, these composite films showed electrochemical activity in their free-standing state. Thus, they can be used as the cathode material for rechargeable battery without conventional metallic or conducting glass sheet as the current collector. Here, carbon fibers act as an electrically conductive skeletal electrode for current collection. The charge capacity of the film with a thickness of 120 μm was tested to be 2.5 coulombs (C)/cm² and a specific capacity of 91 mAh/g. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 2149–2154, 1997     

Polymerization of pyrrole on a polyelectrolyte hollow-capsule microreactor

‘Caved-in’ and spherical polypyrrole (PPy) capsules were successfully prepared by direct polymerization of pyrrole on polyelectrolyte hollow-capsule microreactors at different conditions. This microreactor was formed by alternate layer-by-layer (LbL) adsorption of chitosan (CS) and poly(sodium 4-styrenesulfonate) (PSS) on polystyrene (PS) colloidal particle and followed by removing the PS core with tetrahydrofuran (THF). The integrity and self-sustaining of the microreactor could be ensured through the chemical cross-linking of CS in multilayers with glutaraldehyde before the removing of PS. The direct polymerization of pyrrole on the microreactor, either polycations or polyanions at the outmost layer, can be achieved according to hydrogen bonding effect or electrostatic interaction. Participation of inorganic salts plays a significant role on morphology controllable of intact hollow polypyrrole capsules.     

The effect of pH on the pyrrole electropolymerization on iron in malate aqueous solutions

The influence of pH on pyrrole electropolymerization on iron surfaces in malate aqueous medium was analyzed using different electrochemical techniques. The sodium sulfate solution was used as reference.     

Studies on electro‐conductive yarns prepared by in situ chemical and electrochemical polymerization of pyrrole

This work deals with preparation, characterization, and performance of electro‐conductive yarns prepared by in situ chemical and electrochemical polymerization of pyrrole. Box‐Behnken design in conjunction with response surface analysis has been used to study the electrochemical polymerization process. The effect of electrochemical process parameters on the electrical resistivity has been reported. Further, the electrical and electromechanical behaviour of the electro‐conductive yarns thus produced has also been reported. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Formation and characterization of core-sheath nanofibers through electrospinning and surface-initiated polymerization

Novel core-sheath nanofibers, composed of polyacrylonitrile (PAN) core and polypyrrole (PPy) sheath with clear boundary between them, were fabricated by electrospinning PAN/FeCl₃·6H₂O bicomponent nanofibers and the subsequent surface-initiated polymerization in a pyrrole-containing solution. By adjusting the concentration of FeCl₃·6H₂O, the surface morphology of PPy sheath changed from isolated agglomerates or clusters to relatively uniform thin-film structure. Thermal properties of PAN-PPy core-sheath nanofibers were also characterized. Results indicated that the PPy sheath played a role of inhibitor and retarded the complex chemical reactions of PAN during the carbonization process.     

[Emim]HS04一FeCl3催化1一丁烯齐聚反应研究

制备并以Br6nsted—Lewis双酸性离子液体催化剂[Emim]HSO4-FeCl3催化1-丁烯齐聚反应,分析不同阴阳离子物质的量比、反应温度、反应压力、反应时间等条件对1一丁烯齐聚产物选择性的影响。结果表明,强酸性离子液体催化1丁烯齐聚反应得到的产物主要为四聚物与五聚物。以n（FeCl3）：n（[Emim]Hs04）一1：1,反应温度40℃,反应压力0．1MPa,反应时间1h的工艺条件下进行的齐聚反应,产物的选择性及反应体系的稳定性较为理想。     

Mechanism of electroreduction of intermediates with and without a proton donor

Electrochemistry of various categories of intermediates was comparatively studied over wide range of electrode potentials, concentrations of proton donors (H₃O⁺, NH₄⁺), and temperatures. The suggested kinetic model considered two parallel pathways of electron transfer: either to an adsorbed intermediate (radical) or to the respective metastable complex with a proton donor. The electroreduction of all studied intermediates was found to obey the model. The formation of metastable complexes was shown to be facilitated for radicals having one or more functional groups. The particular reduction pathway is determined predominantly by the difference between overvoltages of electron transfer to a radical and to its metastable complex with a proton donor under the same experimental conditions (i.e. nature and concentration of a proton donor, electrode potential).     

An effective layer-by-layer adsorption and polymerization method to the fabrication of polyoxometalate-polypyrrole nanoparticle ultrathin films

A layer-by-layer (LbL) adsorption and polymerization method was developed for the controllable preparation of polypyrrole (PPy) nanoparticles within ultrathin films. By repetitive adsorption of pyrrole and subsequent polymerization with 12-molybdophosphoric acid, the polyelectrolyte multilayer films containing PPy nanoparticles were fabricated. UV-visible absorption spectrocopy, Fourier transform infrared (FTIR) spectroscopy, atomic force microscopy (AFM), transmission electron microscopy (TEM) and cyclic voltammograms (CVs) were used to characterize the PPy nanoparticles and their multilayer thin films. UV-visible spectra indicate that the growth of PPy nanoparticles was regular and occurred within the polyelectrolyte films. The size of prepared PPy nanoparticles was found by TEM to increase with the increasing of polymerization cycles. The electrochemistry behavior of the multilayer thin films was studied in detail on ITO. The results suggest that the LbL adsorption and polymerization method developed herein provides an effective way to prepare PPy nanoparticles in the polymer matrix.     

Copolymers of pyrrole and N-(hydroxypropyl)pyrrole: properties and interaction with DNA

Copolymers derived from mixtures of pyrrole and N-(hydroxypropyl)pyrrole have been prepared electrochemically using various concentration ratios. Copolymers were generated on stainless electrodes by chronoamperometry and cyclic voltammetry in a LiClO₄ acetonitrile solution. Relevant physical (density and doping level) and electrochemical (electroactivity and electrostability) properties of the copolymers have been examined and compared with those of the two corresponding homopolymers, which were prepared using the same electrochemical procedures. Results show that the copolymer obtained using the 25:75 N-(hydroxypropyl)pyrrole:pyrrole molar ratio presents an interesting behavior. Finally, the ability of the latter copolymer to form specific interactions with plasmid DNA has been compared with that of polypyrrole.     

Diverse catalytic efficiency of nitroxyl radicals tuned by Lewis acids in the oxidation of hydrocarbons

Aerobic oxidation of α-isophorone catalyzed by 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) has achieved comparable performance to that catalyzed by phthalimide-N-oxyl (PINO) with the assistance of Lewis acids (LAs), but the latter efficiency is depressed by LAs. Remarkably changed structural and thermochemical properties of nitroxyl radicals induced by LAs cause the diversely altered reactivity. Persistent and nonconjugated nitroxyl radicals with alkyl groups around N–O parts like TEMPO can be activated, whereas non-persistent ones, with N–O parts conjugated with carbonyl groups like PINO are deactivated by LAs. TEMPO analogues combined with strong but less steric-hindrance LAs exhibit the highest catalytic activity.     

异丁烯齐聚反应精馏的耦合工艺研究

针对异丁烯齐聚反应和产物提纯过程相分离的工业现状,在自行设计的实验装置上进行了异丁烯齐聚催化反应精馏耦合工艺的研究,分别考察了系统操作状态随时间的变化规律和影响反应精馏过程的主要因素。结果表明:为了得到较高的异丁烯转化率和二聚物选择性,采用全回流操作,进料位置宜设在反应段上方;回流温度过低和塔釜温度过高都对过程不利;添加适当的液相惰性组分,有利于改善填料层的分离效果。在转化率相同的情况下,该反应精馏过程的二聚物选择性大大高于固定床微分反应器和高压釜式反应器的实验结果。     

低碳烯烃齐聚合成液体燃料研究进展

以低碳烯烃为原料进行齐聚反应是制取清洁液体燃料的重要途径之一。目前,在烯烃齐聚反应的产业化发展中,开发具有高活性、高稳定性、产物分布集中的多相催化剂仍是重要的研究方向。本文概述了多相催化烯烃齐聚反应在酸性位点以及镍金属位点两种活性中心上的作用机理,并分别对C₂⁼、C₃⁼和混合烯烃的齐聚反应进行介绍;从多相催化剂的优化设计角度,具体包括载体的类型、孔道结构和活性中心的分布状态以及反应条件的优化等方面对当前的研究工作进行了综述。探讨了多相催化烯烃齐聚反应在制备液体燃料中存在的优势和问题,为进一步开发高选择性、长寿命的多相催化剂提供借鉴。     

Syndiospecific oligomerization and polymerization of norbornene with titanium catalysts

Norbornene (NB) has been polymerized with TiCl₄-AlR₂Cl (R = Et, Me, iBu) at various NB/TiCl₄ molar ratio. The products obtained at low ratio (from ca. 5 to 12, depending on the mode of catalyst preparation) are a mixture of oligomers, from which it has been possible to isolate a crystalline heptamer having a 2,3-exo-disyndiotactic structure by single crystal X-ray analysis. The products obtained at higher NB/TiCl₄ ratio have a higher molecular weight (up to ca. 5000 for the soluble products) and consist of amorphous and crystalline polymers. The crystalline polymers, characterized by X-ray and ¹³C NMR, are a new type of stereoregular polynorbornene (PNB), having a 2,3-exo-disyndiotactic structure. Mechanistic aspects are examined and a precise assignment of some resonances in the ¹³C NMR spectrum of vinyl-type PNBs is reported.     

Electrolytic admicellar polymerization of pyrrole on natural rubber/clay nanocomposites

Organic–inorganic composites consisting of natural rubber (NR), polypyrrole (PPy), and sodium montmorillonite (Na‐MMT) were synthesized via electrolytic admicellar polymerization. A constant potential of 9 volts was chosen for the synthesis. The PPy concentration was fixed at 100 mM, and the clay contents were varied from 1 to 7 parts per hundred of rubber (phr). The synthesized nanocomposites were characterized by Fourier transform infrared spectroscopy (FTIR), X‐ray diffraction (XRD), scanning electron microscopy, and transmission electron microscopy (TEM), together with thermal stability (TGA), mechanical properties, and electrical conductivity (σ_dc) studies. The FTIR spectra indicated the characteristic peaks of both PPy and MMT clay and also evidenced a slight interaction between the PPy chain and the clay layers, verifying the success of electrolytic admicellar polymerization. XRD and TEM results pointed out the good dispersion of clay platelets in the polymer matrix, suggesting an exfoliated structure. The morphology of the nanocomposites was greatly dependent on the amount of MMT clay, especially at a 7 phr loading. The initial modulus and tensile strength of the nanocomposites containing the 7 phr loading were about four and two times higher, compared with unfilled NR/PPy, respectively. Thermal stability studies revealed a slight improvement in the decomposition temperature for the PPy component by the clay layers, whereas the opposite trend was found for the NR component. More interestingly, the electrical conductivity of the admicelled rubber increased significantly (～ 19–32 times) with increasing clay contents from 1 to 7 phr, in comparison with unfilled NR/PPy. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009