Electrically Conductive Poly(DL‐lactide)/Chitosan/Polypyrrole Complexes

Summary: The fabrication of novel conductive poly(DL ‐lactide)/chitosan/polypyrrole complex membranes is reported. Using poly(DL ‐lactide)/chitosan blends as matrices and polypyrrole as a conductive component, several kinds of membranes with various compositions are prepared. A percolation threshold of polypyrrole as low as 1.8 wt.‐% is achieved for some membranes by controlling the chitosan proportion between 40 and 50 wt.‐%. SEM images exhibit that the membranes with a low percolation threshold show a two‐phase structure which consists of poly(DL ‐lactide) and chitosan phases. Dielectric measurements indicate that there is limited miscibility between the poly(DL ‐lactide) and chitosan but polypyrrole is nearly immiscible with the other two components. Based on the structural characteristics of the membranes, the polypyrrole particles are suggested to be localized at the interface between two phases.

Dependence of conductivity of complex membranes on the PPy content. (○) PDLLA/PPy, (▪) PDLLA/ch(10)/PPy, (▵) PDLLA/ch(20)/PPy, (•) PDLLA/ch(30)/PPy, (□) PDLLA/ch(40)/PPy, and (▴) PDLLA/ch(50)‐PPy.     

The processing and properties of conductive polypropylene/polypyrrole composites

Polypropylene (PP) particles were chemically coated with polypyrrole (PPy). The content of polypyrrole varied from 0.8 to 7.6 wt.-%. Electrical conductivity of compression moulded samples depends on the concentration of polypyrrole and reached values from 4×10⁻¹⁰ to 5×10⁻³ S/cm, which is about 7 orders of magnitude higher than the conductivity in the blends prepared by mechanical mixing of PP and PPy in the same PPy concentration range. Highly conductive composites were also obtained from a mixture of coated and non-coated PP particles. The PP/PPy composites were characterized by elemental analysis, SEM and mechanical testing. The antistatic properties of PP/PPy composites were demonstrated. The electrical and mechanical properties depend on processing of composites.     

Biodegradability of conducting chitosan-g-polycaprolactone/polypyrrole conduits

Conducting chitosan-g-polycaprolactone(CPC)/polypyrrole(PPy) conduits were fabricated for potential applications in nerve repair. Their mechanical and conducting properties as well as in vitro and in vivo degradation behaviors were mainly examined. It was found that some CPC/PPy conduits showed significantly stronger tensile and lateral compressive strength in the wet state, and notably higher conductivity in the overall tested PPy-load range, in comparison with chitosan/PPy conduits. After being consecutively exposed to PBS systems for various periods up to 10 weeks, the CPC/PPy conduits exhibited relatively slow degradation compared to chitosan/PPy conduits, and their degradation behaviors were measurably mediated by the composition of CPCs. The pH values of media corresponding to some selected CPC/PPy conduits did not significantly deviate from the initial pH value due to the buffering effect of chitosan component. After being implanted into rabbits for various periods, it was observed that the explanted chitosan/PPy conduits could only sustain a very low compressive load after 6-week degradation, and most of them were partially or fully collapsed after 8-week or longer degradation and showed very low conductivity. In contrast to these observations, some explanted CPC/PPy conduits were able to maintain enough strong mechanical strength in the wet state for the required period, and still showed acceptable conducting properties after 10-week in vivo degradation. Results suggested that some CPC/PPy conduits having proper compositional proportions could serve as desirable candidates to bridge nerve gaps in vivo.     

New biocompatible polypyrrole-based films with good blood compatibility and high electrical conductivity

A novel O-butyryl chitosan (OBCS)-grafted polypyrrole (PPy) film was described. The immobilization was accomplished by photocrosslinking the OBCS onto PPy films under ultraviolet light irradiation. The surfaces of OBCS-grafted PPy film were characterized by attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy and electron spectroscopy for chemical analysis (ESCA). The blood compatibility of the OBCS-grafted PPy film was evaluated by platelet-rich plasma (PRP) contacting experiments and protein adsorption experiments in vitro. These results have demonstrated that the surface with immobilized OBCS shows much less platelet adhesive and fibrinogen adsorption compared to the control surface. The bulk conductivity values of PPy films were measured by a modified four-probe method. The composite films have both good blood compatibility and high electrical conductivity that make them suitable for using as potential biomaterials, such as electrically conducting blood vessel and functionally haemocompatible substrate of biosensor used directly in whole blood.     

Synthesis and Characterization of Polypyrrole Nanoparticles and Their Nanocomposites with Poly(propylene)

Summary: Conducting polypyrrole (PPy) nanoparticles were synthesized via microemulsion polymerization. PP/PPy nanocomposites were prepared by melt-mixing of polypyrrole with polypropylene (PP) and processed with injection molding. Tensile tests have revealed that increasing amount of PPy increased the strength and the stiffness of the nanocomposite while limiting the elongation of PP. Thermal gravimetric analysis has showed that incorporation of PPy nanoparticles has improved the thermal stability of the nanocomposites. Increasing amount of PPy nanoparticles increases the conductivity of nonconductive PP up to 2,4.10⁻⁴ Scm⁻¹. The same techniques were used to characterize nanocomposites containing 2% w dispersant. Composites prepared with dispersant have involved smaller dimension PPy nanoparticles and exhibited improvement in some mechanical and thermal properties.     

聚吡咯微粒掺入的聚苯乙烯膜在电解质溶液中的介电弛豫谱及其解析

在40 Hz～11 MHz频率范围测量了聚苯乙烯膜以及混入聚吡咯粒子的聚苯乙烯膜和电解质溶液构成的体系的介电谱, 发现了特异的弛豫现象: 纯的和掺入导电性聚吡咯后的聚苯乙烯膜分别显示出单一弛豫和双弛豫的不同模式的介电谱. 在Maxwell-Wagner界面极化概念基础上解释了该弛豫机制: 高、低频弛豫分别由膜-液界面极化和膜相本身的不均一性引起的. 将体系进行了模型化, 并利用Hanai理论方法对谱进行了解析, 获得了内部电性质的诸多参数. 对不同聚吡咯掺入量的膜/溶液体系的介电测量和解析结果表明, 电解质溶液的种类、浓度以及膜中混入聚吡咯的量都影响着膜相的介电响应. 这些结论为利用加入导电粒子改善绝缘高分子聚合物的电性质的研究以及制备既具有导电功能又使基体的力学性能得到提高的高分子复合物提供了重要的线索.     

Lab Scale Study on Humidity Sensing and D.C. Conductivity of Polypyrrole/Strontium Arsenate (Sr<Subscript>3</Subscript>(AsO<Subscript>4</Subscript>)<Subscript>2</Subscript>) Ceramic Composites

In-situ polymerization of pyrrole was carried out with strontium arsenate (ceramics) in the existence of oxidizing agent ammonium persulphate to synthesize polypyrrole/strontium arsenate composites by chemical oxidation method. The polypyrrole/strontium arsenate composites were synthesized with various compositions viz., 10 to 50 wt % of strontium arsenate was placed in polypyrrole. The surface morphologies of these composites were analyzed using Scanning Electron Microscopy (SEM) which confirmed the embedment of strontium arsenate particles in PPy chain. The Fourier Transform Infra-Red spectra (FTIR) revealed the shift of lengthens frequencies towards elevated frequency area. The powder X-ray diffraction patterns (XRD) disclosed the crystalline behavior exhibition of the composites. Thermographs of thermal analysis (TG/DTA) exposed the stronger stability of polypyrrole/strontium arsenate composites than PPy. D.C. conductivity reveals that, the strontium arsenate concentration in polypyrrole is accountable for the variant of conductivity of the composites. The results of the study signify the increment of D.C. conductivity for 40 wt % of strontium arsenate in polypyrrole. The temperature reliant conductivity dimension shows the thermally activated exponential behavior of PPy/Sr₃(AsO₄)₂ composites. The reduction in electrical resistance was experienced, when the polymer composites were bare to the wide range of relative humidity (Rh) (from 30 to 95%). This reduce is due to enhance in surface electrical conductivity ensuing from humidity fascination and also due to capillary abridgment of water causing change in conductivity within the sensing materials. The composite shows sensitivity in the range 30 to 95% Rh, we also studied response and recovery time.     

单分散核／壳结构导电高分子复合材料的研究（Ⅰ）——单分散核／壳结构聚苯乙烯／聚吡咯的结构表征

导电高分子在光、电、磁等领域表现出的广泛应用前景 ,使它成为材料科学的研究热点 .然而 ,早期发现的导电高分子的不溶不熔性 ,使它在可加工性和机械性能等方面仍面临许多挑战 .核 /壳结构导电高分子与单分散技术的结合 ,无疑为这一领域的研究带来新的生机和活力 .目前仅有的少量文献主要集中报道微米和亚微米级单分散核 /壳导电高分子复合材料的研究 ,大多采用种子乳液聚合法合成 .微米级的种子乳液通常采用以醇为分散介质的分散聚合方法制备 [1～ 3] ,由于种子分散体系要经反复离心分离 ,除去醇类 ,重新分散在水相中再进行核 /壳导电高分…     

Synthesis of graphite nanosheets/AgCl/polypyrrole composites via two-step inverse microemulsion method

An effective process for the synthesis of graphite nanosheets/AgCl/polypyrrole (NanoGs/AgCl/PPy) composites was developed. NanoGs were prepared by treating the expanded graphite with sonication in aqueous alcohol solution. Then nanocomposites were fabricated via in situ polymerization of pyrrole in the presence of NanoGs and AgCl particles through two-step sequentially inverse microemulsion method. The nanoscale dispersion of NanoGs and AgCl particles was evidenced by the SEM and TEM examinations. From the thermogravimetric analysis, the introduction of inorganic nano-AgCl and NanoGs exhibited a beneficial effect on the thermal stability of pure PPy. According to the four-point-probe test, the conductivity of the final NanoGs/AgCl/PPy composites was dramatically increased compared with pure PPy.     

Ferroferric oxide/chitosan scaffolds with three-dimensional oriented structure

A facile approach to construct ferroferric oxide/chitosan composite scaffolds with three-dimensional oriented structure has been explored in this research.Chitosan and ferroferric oxide are co-precipitated by using an in situ precipitation method,and then lyophilized to get the composite scaffolds.XRD indicated that Fe₃O₄ was generated during the gel formation process,and increasing the content of magnetic particles could destruct the crystal structure of chitosan. When the content of magnetic particles is lower than 10%,the layer-by-layer structure and wheel spoke structure arc coexisting in the scaffolds.Increasing the content of magnetic particles,just layer-by-layer structure could be observed in the scaffolds.Ferroferric oxide particles were uniformly distributed in the matrix,the size of which was about 0.48μm in diameter,2μm in length.Porosity of magnetic chitosan composite scaffolds is about 90%.When the ratio of ferroferric oxide to chitosan is 5/100,the compressive strength of the material is 0.4367 MPa,which is much higher than that of pure chitosan scaffolds,indicating that the layer-by-layer and wheel spokes complex structure is beneficial for the improvement of the mechanical properties of chitosan scaffolds.However,increasing the content of ferroferric oxide,the compressive strength of scaffolds decreased,because of the decreasing of chitosan crystallization and aggregation of magnetic particles as stress centralized body.Another reason is that the layer-by-layer and wheel spokes complex structure makes bigger contributions for the compressive strength than the layer-by-layer structure does.Three-dimensional ferroferric oxide/chitosan scaffolds could be used as hyperthermia generator system,improving the local circulation of blood, promoting the aggradation of calcium salt and stimulating bone tissue regeneration.     

钴铁氧体/膨胀石墨及其聚吡咯复合物的制备和油水分离性能

用化学共沉淀法和原位乳液聚合法分别制备了钴铁氧体/膨胀石墨复合微粒(CF/EG)和钴铁氧体/膨胀石墨/聚吡咯复合物(CF/EG/PPy)。用现代分析技术表征了样品的组成、结构、形貌、电-磁性能和油水分离性能。结果表明,CF粒子已填嵌入到膨胀石墨的层间,CF/EG/PPy复合物的核(CF/EG)和壳(PPy)之间存在着一定的相互作用,样品的油水分离效果与膨胀石墨的层间空隙成正比,其次序为:EG>CF/EG>CF/EG/PPy。磁性的CF/EG微粒回收容易,重复使用性能优良,循环5次的效率不低于90%。     

Effects of Reaction Sequence on the Colloidal Polypyrrole Nanostructures and Conductivity

The relationship between nanoscaled morphology and macroscopic electrical conductivity of polypyrrole (PPy) nanostructures was qualitatively investigated. The PPy nanostructures were prepared via microemulsion polymerization using ionic surfactants. The morphology of PPy was influenced by both the type of ionic surfactants and reaction sequences; specifically, the PPy structures were highly influenced by the reaction sequence when anionic surfactant of SDS was used. By changing reaction sequence, a gel-like PPy was formed influencing on the macroscopic electrical conductivity. The results indicate that the macroscopic conductivity of PPy is affected by its nanoscaled structures as determined by the reaction conditions.     

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.     

Highly conductive free standing polypyrrole films prepared by freezing interfacial polymerization

Highly conductive free standing polypyrrole (PPy) films were prepared by a novel freezing interfacial polymerization method. The films exhibit metallic luster and electrical conductivity up to 2000 S cm(-1). By characterizing with SEM, FTIR, Raman and XRD, the high conductivity is attributed to the smooth surface, higher conjugation length and more ordered molecular structure of PPy.     

Preparation and Properties of Composite Polypyrrole/Pt Catalyst Systems

Three different methods for the preparation and modification of conducting polymer/noble metal catalyst systems consisting of polypyrrole (PPy) and platinum (Pt) are described for the anodic oxidation of methanol. The first method consists of the electrochemical deposition of a thin PPy film on glassy carbon substrate, which is modified with Pt either by electroreduction of hexachloroplatinate, codeposition from a nanodispersed Pt solution, or incorporation of tetrachloroplatinate as counterion followed by cathodic reduction. A second method is based on the preparation of nanoscale PPy(PSS) particles by chemical polymerization with polystyrenesulfonate PSS^– as the counterion. This material is a favorable catalyst support for nanodispersed Pt due to its mixed electronic and cationic conductivity. To study the electrochemical properties, the particulate system PPy(PSS)/Pt is fixed in a carbon fiber electrode. A third method was developed which brings the polypyrrole in close contact to a proton exchanger membrane (Nafion) using a special chemical deposition procedure. This method is useful for preparing a membrane electrode assembly (MEA) consisting of Nafion/PPy/Pt. The structural, morphological, and electrocatalytic properties for methanol oxidation were studied depending on the preparation method applied using surface analytical techniques (TEM, SEM, and EDX) and electrochemical measurements (cyclic voltammetry and transient techniques).     

Studies on formation mechanism of polypyrrole microtubule synthesized by template‐free method

The influence of the polymerization time and rate as well as the solution's ionic strength on the morphology, conductivity, and molecular structure of the polypyrrole (PPy) microtubule [synthesized by the template‐free method in the presence of β‐naphthalene sulfonic acid (β‐NSA) as the dopant] were investigated. It was found that the formation of the PPy‐NSA microtubule was a slow and self‐assembled growth process. Moreover, the β‐NSA dopant played a “templatelike” role in the formation of tubular PPy‐NSA, which might be relative to its surfactant characters. This assumption was further confirmed by the phenomenon that the morphology of PPy‐NSA could be modified by increasing the ionic strength by adding inorganic salt. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 997–1004, 2001     

Controlled preparation of core–shell polystyrene/polypyrrole nanocomposite particles by a swelling–diffusion–interfacial polymerization method

Polystyrene/polypyrrole (PS/PPy) core–shell nanocomposite particles with uniform and tailored morphology have been successfully synthesized using the “naked” PS particulate substrate with the aid of a proposed strategy, the so-called swelling–diffusion–interfacial polymerization method. After initially forming pyrrole-swollen PS particles, diffusion of the monomer toward the aqueous phase was controlled through the addition of hydrochloric acid, eventually leading to its polymerization on the substrate particle surface. This process allows the nanocomposite particles to possess uniform and intact PPy overlayer and affords much more effective control over the structure and morphology of the resultant nanocomposites by simply changing the PS/pyrrole weight ratio or the addition amount of the doping acid. In particular, the nanocomposite particles with a thin, uniform, and intact PPy overlayer and their corresponding PPy hollow particles were obtained at a low addition amount of pyrrole. The resultant nanocomposite particles have been extensively characterized using scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, and thermogravimetry.     

Conductive macroporous composite chitosan-carbon nanotube scaffolds

Multiwalled carbon nanotubes (MWCNTs) were used as doping material for three-dimensional chitosan scaffolds to develop a highly conductive, porous, and biocompatible composite material. The porous and interconnected structures were formed by the process of thermally induced phase separation followed by freeze-drying applied to an aqueous solution of 1 wt % chitosan acetic acid. The porosity was characterized to be 97% by both mercury intrusion porosimetry measurements and SEM image analysis. When MWCNTs were used as a filler to introduce conductive pathways throughout the chitosan skeleton, the solubilizing hydrophobic and hydrophilic properties of chitosan established stable polymer/MWCNT solutions that yielded a homogeneous distribution of nanotubes throughout the final composite matrix. A percolation theory threshold of approximately 2.5 wt % MWCNTs was determined by measurement of the conductivity as a function of chitosan/MWCNT ratios. The powder resistivity of completely compressed scaffolds also was measured and was found to be similar for all MWCNT concentrations (0.7-0.15 Omega cm powder resistivity for MWCNTs of 0.8-5 wt %) and almost five times lower than the 20 k Omega cm value found for pure chitosan scaffolds.     

In Situ Synthesis of Robust Conductive Cellulose/Polypyrrole Composite Aerogels and Their Potential Application in Nerve Regeneration

Nanostructured conductive polymers can offer analogous environments for extracellular matrix and induce cellular responses by electric stimulation, however, such materials often lack mechanical strength and tend to collapse under small stresses. We prepared electrically conductive nanoporous materials by coating nanoporous cellulose gels (NCG) with polypyrrole (PPy) nanoparticles, which were synthesized in situ from pyrrole monomers supplied as vapor. The resulting NCG/PPy composite hydrogels were converted to aerogels by drying with supercritical CO₂, giving a density of 0.41–0.53 g cm^?3, nitrogen adsorption surface areas of 264–303 m² g^?1, and high mechanical strength. The NCG/PPy composite hydrogels exhibited an electrical conductivity of up to 0.08 S cm^?1. In vitro studies showed that the incorporation of PPy into an NCG enhances the adhesion and proliferation of PC12 cells. Electrical stimulation demonstrated that PC12 cells attached and extended longer neurites when cultured on NCG/PPy composite gels with DBSA dopant. These materials are promising candidates for applications in nerve regeneration, carbon capture, catalyst supports, and many others.     

金纳米粒子与聚吡咯纳米管的复合及其SERS效应研究

通过柠檬酸盐与HAuCl4水溶液在微沸状态下反应制备的金纳米粒子因其特殊的表面与界面效应在光学、生物学和催化化学领域得到了广泛应用,而聚吡咯(PPy)具有环境稳定性好、电导率高且变化范围大、容易合成等优点,聚吡咯纳米管可用作导电材料、酶封装材料、抗静电材料,也可用于制备传感器、传动器、固体电解质电容器等。