Influence of graphene reinforcement in conductive polymer: Synthesis and characterization

Lightweight conductive polymers are considered for lightning strike mitigation in composites by synthesizing intrinsically conductive polymers (ICPs) and by the inclusion of conductive fillers in insulating matrices. Conductive films based on polyaniline (PANI) and graphene have been developed to improve through‐thickness conductivity of polymer composites. The result shows that the conductivity of PANI enhanced by blending polyvinylpyrrolidone (PVP) and PANI in 3:1 ratio. Conductive composite thin films are prepared by dispersing graphene in PANI. The conductivity of composite films was found to increase by 40× at 20 wt% of graphene inclusion compared with PVP and PANI blend. Fourier‐transform‐infrared (FTIR) spectra confirmed in situ polymerization of the polymer blend. The inclusion of graphene also exhibits an increase in Tg by 21°C. Graphene additions also showed an increase in thermal stability by approximately 148°C in the composite films. The mechanical result obtained from DMA shows that inclusion of graphene increases the tensile strength by 48% at 20 wt% of graphene reinforcement. A thin, highly conductive surface that is compatible with a composite resin system can enhance the surface conductivity of composites, improving its lightning strike mitigation capabilities.     

Recent Progress in the Development of Conducting Polymer‐Based Nanocomposites for Electrochemical Biosensors Applications: A Mini‐Review

Among various immobilizing materials, conductive polymer‐based nanocomposites have been widely applied to fabricate the biosensors, because of their outstanding properties such as excellent electrocatalytic activity, high conductivity, and strong adsorptive ability compared to conventional conductive polymers. Electrochemical biosensors have played a significant role in delivering the diagnostic information and therapy monitoring in a rapid, simple, and low cost portable device. This paper reviews the recent developments in conductive polymer‐based nanocomposites and their applications in electrochemical biosensors. The article starts with a general and concise comparison between the properties of conducting polymers and conducting polymer nanocomposites. Next, the current applications of conductive polymer‐based nanocomposites of some important conducting polymers such as PANI, PPy, and PEDOT in enzymatic and nonenzymatic electrochemical biosensors are overviewed. This review article covers an 8‐year period beginning in 2010.     

Nanoscale measurements of conducting domains and current-voltage characteristics of chemically deposited polyaniline films

Spatial variations in electric conductivity and evolutions of band structures of polyaniline (PANI) films have been studied by use of a so-called current-sensing atomic force microscope (CS-AFM) or atomic force microscope current image tunneling spectroscopy (AFM-CITS). PANI films were deposited chemically onto indium-tin oxide- (ITO-) glass substrates, and their thickness and doping levels were controlled by polymerization and acid-doping conditions. The conducting uniformity of the PANI films depends on their doping level and thickness. Conducting domains were observed in fully doped PANI film, even when the bias voltage was reduced to as small as 30 mV. High current flowing regions gradually disappeared when conducting PANI films were partially dedoped. The point-contact current-voltage (I-V) characteristics of conducting tip-polymer/ITO systems were investigated on PANI films with different thickness and degree of doping. Various types of I-V curves representing metallic, semiconducting, and insulating states were obtained depending on the aggregation of polymer chains and doping level of the polymer film. The band gap energies (estimated from the I-V or dI/dV-V curves) of emeraldine base (EB) (undoped polyaniline) films are all higher than 3.8 eV, and a wide distribution of the band gap energies (0-1.1 eV and 0.75-1.8 eV for fully and partially doped PANI thin films, respectively) was found in a single polymer film.     

Conductivity and structure of melt‐processed polyaniline binary and ternary blends

In the present study, conductive binary and ternary blends containing polyaniline (PANI) were developed through melt blending. The binary blends' investigation focused on the morphology, in light of the components' interaction, and the resulting electrical conductivity. Similar solubility parameters of a given doped PANI and a matrix polymer lead to dispersion of fine PANI particles within the matrix, and to formation of conducting paths at low PANI contents. A plasticizer acting also as a compatibilizer improves the matrix polymer/PANI interactions. In ternary blends consisting of PANI and two immiscible polymers, the PANI preferrentially locates in one of the components, affecting the blend's morphology. This “concentrating” effect leads to relatively high electrical conductivity at a low PANI content. The electrical conductivity of the studied ternary blends is almost independent of the components' sequence of addition into the hot melt mixing device, exhibiting the selectivity of PANI towards one of the components. Copyright © 2000 John Wiley & Sons, Ltd.     

Electric field sensitivity of conducting hydrogels with interpenetrating polymer network structure

In this article, we reported the synthesis, structure and electric field sensitivity of polyacrylate/polyaniline (PAA/PANI) and poly(2-acrylamido-2-methyl propylsulfonic acid-acrylic acid)/polyaniline [P(AMPS-AA)/PANI] conducting hydrogels with an interpenetrating polymer network (IPN) structure. Scanning electron microscope showed that the conducting hydrogels presented porous structures consisting of PANI nanofibers. The results of Fourier-transform infrared and X-ray diffraction revealed that the PANI was in its conductive emeraldine state and partial crystallization. The unique morphology and molecular structure of the conducting hydrogels were expected to show unusual electric field responses. The conducting hydrogels were subjected to an electric field in NaCl solution for bending behaviors. It was demonstrated that the electric field response was improved by increasing aniline dosage, applied voltage and concentration of aqueous NaCl solution. The bending mechanism was attributed to polyelectrolyte hydrogel matrix and emeraldine PANI nanofibers.     

Electrospinning of Hyperbranched Poly-L-Lysine/Polyaniline Nanofibers for Application in Cardiac Tissue Engineering

Electrospun polyaniline nanofibers are one of the most promising materials for cardiac tissue engineering due to their tunable electroactive properties. Moreover, the biocompatibility of polyaniline nanofibes can be improved by grafting of adhesive peptides during the synthesis. In this paper, we describe the biocompatible properties and cardiomyocytes proliferation on polyaniline electrospun nanofibers modified by hyperbranched poly-L-lysine dendrimers (HPLys). The microstructure characterization of the HPLys/polyaniline nanofibers was carried out by scanning electron microscopy (SEM). It was observed that the application of electrical current stimulates the differentiation of cardiac cells cultured on the nanofiber scaffolds. Both electroactivity and biocompatibility of the HPLys based nanofibers suggest the use this material for culture of cardiac cells and opens the possibility of using this material as a biocompatible electroactive 3-D matrix in cardiac tissue engineering.     

Electrically conductive,melt‐processed ternary blends of polyaniline/dodecylbenzene sulfonic acid,ethylene/vinyl acetate,and low‐density polyethylene

Although polyaniline (PANI) has high conductivity and relatively good environmental and thermal stability and is easily synthesized, the intractability of this intrinsically conducting polymer with a melting procedure prevents extensive applications. This work was designed to process PANI with a melting blend method with current thermoplastic polymers. PANI in an emeraldine base form was plasticized and doped with dodecylbenzene sulfonic acid (DBSA) to prepare a conductive complex (PANI–DBSA). PANI–DBSA, low‐density polyethylene (LDPE), and an ethylene/vinyl acetate copolymer (EVA) were blended in a twin‐rotor mixer. The blending procedure was monitored, including the changes in the temperature, torque moment, and work. As expected, the conductivity of ternary PANI–DBSA/LDPE/EVA was higher by one order of magnitude than that of binary PANI–DBSA/LDPE, and this was attributed to the PANI–DBSA phase being preferentially located in the EVA phase. An investigation of the morphology of the polymer blends with high‐resolution optical microscopy indicated that PANI–DBSA formed a conducting network at a high concentration of PANI–DBSA. The thermal and crystalline properties of the polymer blends were measured with differential scanning calorimetry. The mechanical properties were also measured. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3750–3758, 2004     

Preparation of polyaniline conductive composites with diene‐rubber or polyphenylacetylene

We describe the preparation of polyaniline (PANI‐EB) by aniline oxidation with KIO₃ and the purification of the resulting dedoped polymer by an acetone extraction step to eliminate undesired by‐products from polyaniline, which could generate some safety concerns in the application and use of PANI. Excellent homogeneous and electrically conducting composite films can be prepared from chloroform solutions of purified PANI doped with camphorsulfonic acid in presence of cis‐1,4‐polybutadiene as the film‐forming agent. These films have been characterized by FT‐IR and UV‐VIS‐NIR spectroscopy. A method to synthesisze PANI directly doped with dodecylbenzenesulfonic acid (DBSA) is also reported. DBSA‐doped‐PANI was then used to prepare composites with polyphenylacetylene (PPA) by growing homogeneous films from chloroform solution. These films were conductive and were studied by FT‐IR and UV‐VIS‐NIR spectroscopy. In view of the application of these composites as gas sensors or in “electronic noses”, a short discussion is presented about the criteria used in the selection of the chemical nature of the host polymer where doped PANI is included to confer electrical conductivity. The interaction between the molecules to be detected and the polymeric sensing surface is discussed in terms of physisorption, chemisorption and charge‐transfer‐complex formation. Copyright © 2001 John Wiley & Sons, Ltd.     

Changes During Storage of Electrically Conductive Blends Polyaniline–Poly(Ethylene‐co‐vinyl Acetate)

Abstract

The electrical conductivity behavior of polyaniline–poly(ethylene‐co‐vinyl acetate) (PANI–EVA) blends was variable and dynamic during their storage. It was shown that the apparent concentration of the intrinsically conductive polymer at which a conductivity jump of the blends occurs (Φ _c ) is not a constant value over time. The electrical conductivity of the films of low PANI content (below 2.5 wt.%) increased by several (ca. 5) orders of magnitude. It was found that the PANI phase undergoes a flocculation process subsequently resulting in the formation of conductive pathways and a continuous network. Besides, the shape of percolation curves was found to change during storage of the films. Decreased conductivity deviations were registered for blends of low PANI content (<2.5 wt.%), indicating that an improvement (or decreasing number of defects) of the conductive pathways took place within the bulk of the insulating EVA matrix. These results and observed phenomena are discussed by means of the interfacial model for electrically conductive polymer blends. They supported the dispersion/flocculation phase transition within similar composite materials. The phase separation and conductivity jump are attributed to the interfacial interactions between the polymeric constituents. It was shown that the microstructure of the blends consists of highly ordered PANI paths embedded in the insulating EVA matrix. Long fibrils of PANI and interconnected fractal‐like networks were observed. It was found that the sizes of the PANI domains also varied during storage of the films. Due to the spontaneous flocculation of the primary PANI particles, conductive pathways are formed at extremely low percolation threshold (Φ _c , loading level ca. 5 × 10^?3 wt. fraction). Thus, an important property of the conductive constituent, namely its solid‐state rearrangement, was proved. This PANI self‐organization is also interpreted according to the interfacial model of polymer composites. On the other hand, the competition between self‐organization of the complex of PANI with dodecylbenzenesulfonic acid and crystallization of EVA matrix has resulted in structural changes and formation of continuous conductive networks within the blends, responsible for their significantly increased conductivity.     

Nanostructures and Functionalities in Polymer Thin Films

Several examples of self-organization in thin polymer films are considered for the fabrication of nanopatterned surfaces and nanoscopic objects. Mixed polymer brushes of statistical distribution at the surface, composed of two immiscible polymers covalently bonded to the substrate phase, segregate in the sub-micrometer scale. Interplay between lateral and perpendicular (sandwich-like) segregation effects switching behavior of the thin films upon exposure to different environments. The switching between brush morphologies is used for the fabrication of adaptive/responsive surfaces. Fabrication of nano-domains based on microphase segregation in block-copolymer systems is used for structures with lateral dimensions as small as 5-50 nm. The ordered copolymer structures are applied as templates for the fabrication of membranes, nanofibers and nanoparticles.     

Investigation on the effects of beta and gamma irradiation on conducting polymers for sensor applications

Two conductive polymers were evaluated to be the active materials in a sensor device for the detection of beta radiation. This was accomplished by characterizing the changes in conductivity of electrically conducting polymer films caused by exposure to tritium gas for varying lengths of time. The behavior of these materials when exposed to gamma radiation was also studied to gain further insight into the mechanism of conductivity degradation by ionizing radiation. Two types of conductive polymer, polyaniline (PANi) and poly(3,4-ethylenedioxythiophene) (PEDOT), were chosen as candidate materials for their widespread commercial use. The change of surface resistance (conductivity) of PANi and PEDOT films when exposed to gamma radiation in both air and deuterium environments was evaluated as well as tritium exposures in 10⁴ and 10⁵ Pa gas. Raman and absorbance spectra of gamma irradiated samples were obtained to determine the mechanism of conductivity degradation in both polymers. Post-irradiation gas analysis of the samples contained in deuterium revealed very little (or no) hydrogen in the containment vessel, indicating that hydrogen–deuterium isotopic exchange was not responsible for the decrease in surface conductivity due to gamma exposure. The effects of irradiation-induced oxidation were also studied for both conductive polymers during gamma irradiation. It was concluded that chain scission via free radical formation and chain cross-linking are most likely the two dominant mechanisms for conductivity change and not de-protonation of the polymer.     

Development of conductive bacterial cellulose foams using acoustic cavitation

Bacterial cellulose (BC) has found applications in various fields ranging from healthcare to electronics. Functionalization of cellulose to impart conductive properties has been met with challenges due to superficial coating rather than uniform interactions with the conducting polymers. In this work, mechanical disruption is shown to be a facile strategy to develop BC-PEDOT:PSS conductive foams without the use of any harsh chemical treatments to functionalize cellulose. The strategy allows for uniform polymer intercalation with the cellulose nanofibers imparting superior conductive properties to the functional material. The conductive foams with low PEDOT:PSS ratio exhibit conductivity of 0.7 S/cm and are cytocompatible with human dermal fibroblasts (HDFa) cells.

     

Composites of polyaniline nanofibers and molecularly imprinted polymers for recognition of nitroaromatic compounds

This paper reports a monomer strategy for imprinting of 1,3-dinitrobenzene (DNB) molecules at the surface of conductive functional polyaniline nanofibers (PANI) for the first time. It has been demonstrated that the vinyl functional monomer layer on the PANI surface can not only direct the selective occurrence of imprinting polymerization, but can also drive DNB templates into the polymer through charge-transfer complexing interactions between DNB and functionalized PANI. These two basic processes lead to the formation of DNB-imprinted polymers at the surface of polyaniline nanofibers. The capacity to uptake DNB shows that selectivity coefficient in the nanofibers polymers is nearly three times as high as that of traditional imprinted materials and the nanofibers polymers also possess high selectivity toward DNB in comparison to similar nitroaromatic compounds. A linear response of DNB concentration between 2.20×10(-8) and 3.08×10(-6) M was exhibited with a detection limit of 7.33×10(-9) M (S/N=3). These results reported here could form the basis of a new strategy for preparing various polymer-coating layers on polyaniline supports and the molecular imprinting techniques discussed could also find applications in the fields of separation, trace detection, and environmental monitoring.     

Electrospun antimony doped tin oxide (ATO) nanofibers as a versatile conducting matrix

Nanoparticles of ATO (antimony doped tin oxide) were used to produce thick conductive, free standing mats of nanofibers via electrospinning. These fibrous mats were incorporated into polymer films to produce a transparent conducting polymer foil. Moreover, the fiber mats can serve as porous electrodes for electrodeposition of Prussian Blue and TiO(2) and were tested in dye-sensitized solar cells.     

多功能性聚吡咯复合膜

聚吡咯具有较高的电导率与良好的环境稳定性,被视为继聚苯胺之后最有工业化应用前景的导电高分子材料之一。聚吡咯与常规聚合物基体如聚乙烯醇、聚氯乙烯等形成的复合膜不仅可以综合聚吡咯奇异的多功能性与常规聚合物的易成膜性和低成本性于一体,而且可望发挥两者的协同效应,从而大大拓宽其应用领域。该研究已经成为导电聚合物研究领域中的又一新热点。作者系统论述了制备这类功能复合膜的两种典型制备方法,并在分析各自特点的基础上提出了改进与发展方向,指出聚吡咯复合膜具有广泛可调的电导率、快速的电学响应性以及稳定的电致变色性等多种功能,在透明导电膜、化学传感器、生物分离膜、电致变色膜领域具有诱人的应用前景。     

Modifying thermal transport in electrically conducting polymers: effects of stretching and combining polymer chains

If their thermal conductivity can be lowered, polyacetylene (PA) and polyaniline (PANI) offer examples of electrically conducting polymers that can have potential use as thermoelectrics. Thermal transport in such polymers is primarily influenced by bonded interactions and chain orientations relative to the direction of heat transfer. We employ molecular dynamics simulations to investigate two mechanisms to control the phonon thermal transport in PANI and PA, namely, (1) mechanical strain and (2) polymer combinations. The molecular configurations of PA and PANI have a significant influence on their thermal transport characteristics. The axial thermal conductivity increases when a polymer is axially stretched but decreases under transverse tension. Since the strain dependence of the thermal conductivity is related to the phonon scattering among neighboring polymer chains, this behavior is examined through Herman's orientation factor that quantifies the degree of chain alignment in a given direction. The conductivity is enhanced as adjacent chains become more aligned along the direction of heat conduction but diminishes when they are orthogonally oriented to it. Physically combining these polymers reduces the thermal conductivity, which reaches a minimum value for a 2:3 PANI/PA chain ratio.     

静电纺丝制备荧光导电双功能复合纳米纤维及其表征

采用静电纺丝技术将导电聚苯胺(PANI)和铕/铽稀土配合物掺杂到高分子基质聚乙烯吡咯烷酮(PVP)中,制备出荧光导电复合纳米纤维。用扫描电镜(SEM)、荧光光谱仪(FL)、宽频介电松驰谱仪对荧光导电复合纳米纤维的性能进行分析,结果显示,在270nm紫外光激发下,铕系列与铽系列复合纳米纤维分别发出红光和绿光。同时,复合纳米纤维的电导率可以达到1.18×10~(-6) S/cm,两种复合纳米纤维同时具有优异的荧光性能及良好的导电功能。     

Transparent conductive films based on polymer composites containing the mixed‐valence tetrathiafulvalene nanofibers

We report the facile preparation of the conductive polymer composites containing the mixed‐valence tetrathiafulvalene (TTF) nanofibers and their applications as all‐organic transparent conductive materials. TTF can be used as a nanofiller for transforming conventional polymers to conductive materials. Self‐assemble nanofibers of the neutral and radical cation of TTF can be formed in the polymer solutions during the film deposition, and the resulting composite films with several micron thickness can serve as the conductive material with high transparency. Several kinds of conventional polymers, such as polystyrene, poly(methyl methacrylate) (PMMA), and poly(vinylpyrrolidone), can be used as a polymer matrix of the composites. The conductivities of the PMMA film containing 35 mol % of the mixed‐valence TTF and the PEDOT–PSS film showed similar values (2.8 × 10^–2 and 5.4 × 10^–1 S/cm, respectively). In contrast, the normalized transmittance of the PMMA film by 1‐μm thickness greatly increased (96%/μm) when compared with that of the PEDOT–PSS film (10%/μm). In addition, the degradation of the conductivity of the nanofibers by heating and aging was effectively suppressed in the composite samples. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6441–6450, 2009     

Self-assembled networks of conducting polyaniline in bulk polymers: A new class of conducting polymer blends

This review of the current status of conducting polymers will focus on recent progress which demonstrates that the initial promise of the late 1970's has become reality. Conducting polymers are now available as materials with truly unique properties: They combine the important electronic and optical properties of semiconductors and metals with the attractive mechanical properties and processing advantages of polymers. Conducting polymer blends based upon polyaniline (PANI) are a new class of materials in which the threshold for the onset of electrical conductivity (σ) can be reduced to volume fractions below 1%, well below that required for classical percolation (16% by volume for globular conducting objects dispersed in an insulating matrix in three dimensions). The origin of this remarkably low threshold for the onset of electrical conductivity is the self-assembled network morphology of the PANI polyblends which forms during the course of liquid-liquid separation. Since the average density of the conducting network near threshold is small, the conductivity increases smoothly and continuously over many orders of magnitude as the concentration of conducting polymer increases above threshold. The low percolation threshold and the continuous increase of σ(f) above threshold are particularly important; as a result of this combination, conducting polyblends can be reproducibly fabricated with controlled levels of electrical conductivity while retaining the desired mechanical properties of the matrix polymer.^1-3)     

Printing polyaniline for sensor applications

In recent years, much research has focused on the development of low-cost, printed electrochemical sensor platforms for environmental monitoring and clinical diagnostics. Much effort in this area has been based on utilising the redox properties of conducting polymers, particularly polyaniline (PANI). In tackling the inherent lack of processability exhibited by these materials, several groups have examined various mass-amenable fabrication approaches to obtain suitable thin films of PANI for sensing applications. Specifically, the approaches investigated over the years include the in situ chemical synthesis of PANI, the use of sulphonated derivatives of PANI and the synthesis of aqueousbased nano-dispersions of PANI. Nano-dispersions have shown a great deal of promise for sensing applications, given that they are inkjet-printable, facilitating the patterning of conducting polymer directly to the substrate. We have shown that inkjet-printed films of PANI can be finely controlled in terms of their two-dimensional pattern, thickness, and conductivity, highlighting the level of precision achievable by inkjet printing. Utilising these nanomaterials as inkjet-printable inks opens novel, facile, and economical possibilities for conducting polymer-printed electronic applications in areas of sensing, but also many other application areas such as energy storage, displays, organic light-emitting diodes. Given that inkjet-printing is a scalable manufacturing technique, it renders possible the large-scale production of devices such as sensors for a range of applications. Several successes have emerged from our work and from the work of others in the area of applying PANI in low-cost sensor applications, which is the focus of this review.