In this work a new method for crosslinking ultra-thin films with potential applications in sensor systems is proposed. The films were produced by layer-by-layer (LbL) assembly using a conducting polymer, poly(o-ethoxyaniline) (POEA), alternated with a thermosetting resin, novolac-type phenolformaldehyde (PF), crosslinked by a simple thermal treatment. The PF resin served as both alternating and crosslinking agents. The films were characterized by Fourier transform infrared (FTIR) and ultraviolet-visible (UV-Vis) spectroscopy, thermogravimetry (TG), desorption, doping/dedoping cycling and electrical measurements. The results showed that film architecture and crosslinking degree can be controlled by the conditions used for film deposition (number of bilayers, polymer concentration, pH, and deposition time), and crosslinking time. Moreover, this approach offers several advantages such as fast curing time and low cost, indicating that these films can be used to produce sensors with improved stability.
Thermally stable elastomeric composites based on ethylene-propylene-diene monomer (EPDM) and conducting polymer-modified carbon black (CPMCB) additives were produced by casting and crosslinked by compression molding. CPMCB represent a novel thermally stable conductive compound made via ""in situ"" deposition of intrinsically conducting polymers (ICP) such as polyaniline or polypyrrole on carbon black particles. Thermogravimetric analysis showed that the composites are thermally stable with no appreciable degradation at ca. 300 degrees C. Incorporating CPMCB has been found to be advantageous to the processing of composites, as the presence of ICP lead to a better distribution of the filler within the rubber matrix, as confirmed by morphological analysis. These materials have a percolation threshold range of 5-10 phr depending on the formulation and electrical dc conductivity values in the range of 1 x 10(-3) to 1 x 10(-2) S cm(-1) above the percolation threshold. A less pronounced reinforcing effect was observed in composites produced with ICP-modified additives in relation to those produced only with carbon black. The results obtained in this study show the feasibility of this method for producing stable, electrically conducting composites with elastomeric characteristics. POLYM. COMPOS....
The corrosion protection of AA6063 aluminium alloy by cerium conversion, polyaniline conducting polymer and by duplex coatings has been investigated. The electrochemical behaviour was evaluated in aerated 3.5 wt.% NaCl. All coatings tested shifted the corrosion and pitting potentials to more positive values, indicating protection against corrosion. The duplex coatings are significantly more effective than each coating alone: corrosion and pitting potentials were shifted by +183 and +417 mV(SCE), respectively, by duplex coatings in relation to the untreated aluminium alloy. Optical microscopy and scanning electron microscopy are in agreement with the electrochemical results, reinforcing the superior performance of duplex coatings. (C) 2012 Elsevier Ltd. All rights reserved.; Brazilian funding agency CNPq [140402/2009-8, 160466/2011-3]; Brazilian funding agency CNPq; Brazilian funding agency CAPES; Brazilian funding agency CAPES [BEX 4935/10-1]; Portuguese funding agency FCT; Portuguese funding agency FCT [CEMUC(R) (Research Unit 285)]
Neste trabalho estudamos duas classes diferentes de materiais condutores através de várias técnicas: o polímero condutor eletrônico Poliparafenileno (PPP) dopado com FeCl3, e os compostos condutores iônicos orgânico-inorgânico complexados com LiClO4, chamados ormolitas. Um estudo comparativo de PPP dopado com FeCl3, por RMN de Alta Resolução em Sólidos de 13C , Ressonância Paramagnética Eletrônica, Susceptibilidade Magnética e Condutividade Elétrica foi realizado em função da concentração de Fe e da temperatura. Observou-se uma forte influência do íon paramagnético Fe3+ na largura de linha e nos tempos de relaxação spin-rede medidos por RMN de alta resolução através do 13C. OS resultados obtidos pelos diferentes métodos estão correlacionados e podem ser explicados pelo modelo polaron-bipolaron. Duas famílias de ormolitas, foram preparadas pelo processo sol-gel. Um estudo comparativo destes compostos por RMN de alta resolução multinuclear, Calorimetria Diferencial (DSC) e Condutividade Elétrica foi feito em função da concentração de lítio, do comprimento da cadeia polimérica, da razão polímero-sílica e da temperatura. Através das medidas de largura de linha dos espectros de RMN em função da temperatura...
We address here some of the issues relating to conducting polymer based devices. We examine the effects of polymer disorder on charge injection, transport, trapping and recombination in light-emitting diodes (LEDs) using a mesoscopic model which includes specific realizations of the electroluminescent polymer network. A key point of this model is to consider both the intermolecular and the interdomain charge carrier transport which are strongly influenced by structural polymer disorder. Simulations of bipolar charge evolution (electrons and holes) through a polydiacetylene (PDA) film, which are injected in the polymer layer from the appropriated electrodes, have been used to give some insights to the issue concerning the fraction of polymer molecules contributing to the conduction process as well as to light emission. The effect of charge traps, such as cross-links, on space charge and recombination is also discussed.
The injection of charge carriers in conducting polymer layers gives rise to local electric fields which should have serious implications on the charge transport through the polymer layer. The charge distribution and the related electric field inside the ensemble of polymer molecules, with different molecular arrangements at nanoscale, determine whether or not intra-molecular charge transport takes place and the preferential direction for charge hopping between neighbouring molecules. Consequently, these factors play a significant role in the competition between current flow, charge trapping and recombination in polymer-based electronic devices. By suitable Monte Carlo calculations, we simulated the continuous injection of electrons and holes into polymer layers of polydiacetylene with different microstructures and followed their transport through those polymer networks. Results of these simulations provided a detailed picture of charge and electric field distribution in the polymer layer and allowed us to assess the consequences for current transport and recombination efficiency as well as the distribution of recombination events within the polymer film. In the steady state we found an accumulation of electrons and holes near the collecting electrodes giving rise to an internal electric field which is greater than the external applied field close to the electrodes and lower than that one in the central region of the polymer layer. We also found that a strong variation of electric field inside the polymer layer leads to an increase of recombination events in regions inside the polymer layer where the values of the internal electric field are lower.; Fundação para a Ciência e a Tecnologia (FCT) ; Programa Operacional “Ciência ...
In this paper we describe interactions between neural cells and the conducting polymer poly(3,4-ethylenedioxythiophene (PEDOT) toward development of electrically conductive biomaterials intended for direct, functional contact with electrically-active tissues such as the nervous system, heart, and skeletal muscle. We introduce a process for polymerizing PEDOT around living cells and describe a neural cell-templated conducting polymer coating for microelectrodes and a hybrid conducting polymer-live neural cell electrode. We found that neural cells could be exposed to working concentrations (0.01 M) of the EDOT monomer for as long as 72 hours while maintaining 80% cell viability. PEDOT could be electrochemically deposited around neurons cultured on electrodes using 0.5-1 μA/mm2 galvanostatic current. PEDOT polymerized on the electrode and surrounded the cells, covering cell processes. The polymerization was impeded in regions where cells were well-adhered to the substrate. The cells could be removed from the PEDOT matrix to generate a neural cell-templated biomimetic conductive substrate with cell-shaped features that were cell-attracting. Live cells embedded within the conductive polymer matrix remained viable for at least 120 hours following polymerization. Dying cells primarily underwent apoptotic cell death. PEDOT...
Conducting polymer nanostructures have received increasing attention in both fundamental research and various application fields in recent decades. Compared with bulk conducting polymers, conducting polymer nanostructures are expected to display improved performance in energy storage because of the unique properties arising from their nanoscaled size: high electrical conductivity, large surface area, short path lengths for the transport of ions, and high electrochemical activity. Template methods are emerging for a sort of facile, efficient, and highly controllable synthesis of conducting polymer nanostructures. This paper reviews template synthesis routes for conducting polymer nanostructures, including soft and hard template methods, as well as its mechanisms. The application of conducting polymer mesostructures in energy storage devices, such as supercapacitors and rechargeable batteries, are discussed.
An in vitro comparison of conducting-polymer nanotubes of poly(3,4-ethylenedioxythiophene) (PEDOT) and poly(pyrrole) (PPy) and to their film counterparts is reported. Impedance, charge-capacity density (CCD), tendency towards delamination, and neurite outgrowth are compared. For the same deposition charge density, PPy films and nanotubes grow relatively faster vertically, while PEDOT films and nanotubes grow more laterally. For the same deposition charge density (1.44 C cm–2), PPy nanotubes and PEDOT nanotubes have lower impedance (19.5 ± 2.1 kΩ for PPy nanotubes and 2.5 ± 1.4 kΩ for PEDOT nanotubes at 1 kHz) and higher CCD (184 ± 5.3 mC cm–2 for PPy nanotubes and 392 ± 6.2 mC cm–2 for PEDOT nanotubes) compared to their film counterparts. However, PEDOT nanotubes decrease the impedance of neural-electrode sites by about two orders of magnitude (bare iridium 468.8 ± 13.3 kΩ at 1 kHz) and increase capacity of charge density by about three orders of magnitude (bare iridium 0.1 ± 0.5 mC cm–2). During cyclic voltammetry measurements, both PPy and PEDOT nanotubes remain adherent on the surface of the silicon dioxide while PPy and PEDOT films delaminate. In experiments of primary neurons with conducting-polymer nanotubes...
Carborane-functionalized conducting polymer films have been
electrogenerated in dichloromethane from the anodic oxidation of
ortho- (1), meta-
(3) and para-carborane (4)
isomers linked to two 2-thienyl units. The corresponding electrochemical
response was characterized by a broad reversible redox system corresponding to
the p-doping/undoping of the polythiophene backbone, the formal potential of
which increased in the order poly(1) < poly(3) <
poly(4), from ca. 0.50 to 1.15 V vs Ag/Ag+
10−2 M. From further UV–visible spectroscopy
analysis, the optical band gap was estimated at 1.8, 2.0 and 2.2 eV for
poly(1), poly(3) and poly(4),
respectively. The more conjugated and electroconductive character of
poly(1) is ascribed to a more planar conformation of the
conjugated backbone resulting from an intramolecular
β–β′ cyclization reaction
in the monomer, consequently yielding a fused conjugated polymer. Molecular
modeling calculations using the DFT method support this hypothesis. The surface
topography and maps of the conductive domains of the electropolymerized films
were evaluated by conducting probe AFM. The three polymers exhibit fairly
similar morphological characteristics and a surface roughness of ~2 nm.
Current–voltage (I–V) characteristics of
conducting AFM tip-carborane polymer–ITO junctions showed that
poly(1) had the highest conductivity.
Conducting polymer 3D microelectrodes have been fabricated for possible future neurological applications. A combination of micro-fabrication techniques and chemical polymerization methods has been used to create pillar electrodes in polyaniline and polypyrrole. The thin polymer films obtained showed uniformity and good adhesion to both horizontal and vertical surfaces. Electrodes in combination with metal/conducting polymer materials have been characterized by cyclic voltammetry and the presence of the conducting polymer film has shown to increase the electrochemical activity when compared with electrodes coated with only metal. An electrochemical characterization of gold/polypyrrole electrodes showed exceptional electrochemical behavior and activity. PC12 cells were finally cultured on the investigated materials as a preliminary biocompatibility assessment. These results show that the described electrodes are possibly suitable for future in-vitro neurological measurements.
Many research studies have been conducted on the use of conjugated polymers in the construction of chemical sensors including potentiometric, conductometric and amperometric sensors or biosensors over the last decade. The induction of conductivity on conjugated polymers by treating them with suitable oxidizing agents won Heeger, MacDiarmid and Shirakawa the 2000 Nobel Prize in Chemistry. Common conjugated polymers are poly(acetylene)s, poly(pyrrole)s, poly(thiophene)s, poly(terthiophene)s, poly(aniline)s, poly(fluorine)s, poly(3-alkylthiophene)s, polytetrathiafulvalenes, poly-napthalenes, poly(p-phenylene sulfide), poly(p-phenylenevinylene)s, poly(3,4-ethylene-dioxythiophene), polyparaphenylene, polyazulene, polyparaphenylene sulfide, poly-carbazole and polydiaminonaphthalene. More than 60 sensors for inorganic cations and anions with different characteristics based on conducting polymers have been reported. There have also been reports on the application of non-conducting polymers (nCPs), i.e. PVC, in the construction of potentiometric membrane sensors for determination of more than 60 inorganic cations and anions. However, the leakage of ionophores from the membranes based on these polymers leads to relatively lower life times. In this article...
Conducting polymers as a class of materials can be used to build a diverse range of devices. Conducting polymer based actuators (muscles), transistors (neurons), strain gages (muscle spindles), force sensors (Golgi tendon organs), light emitting diodes, photodetectors (eyes), batteries and supercapacitors (energy storage), and chemical sensors (noses) can all be manufactured. The range of behaviors makes conducting polymers the only class of materials that might be able to mimic the full range of functions needed to build a truly lifelike artificial system. In this thesis, a conducting polymer actuator and conducting polymer strain gage are used for the first time to build a reflex or position feedback loop that rejects position disturbances. The successful operation of the conducting polymer based reflex loop is an important step towards building an all polymer reflex loop that is directly integrated into a bulk material. Such a reflex loop could be used to control position, to control force or to dynamically change the material stiffness and viscosity. In the course of the project, an improved understanding of conducting polymer actuators has led to mathematical descriptions of the charging and discharging of long linear actuators and to equations describing the deflection and force of three layer bending beam actuators. These equations can be used as design tools to build actuators that satisfy given performance requirements. Finally...
Conducting polymers are a promising class of electroactive materials that undergo volumetric changes under applied potentials, which make them particularly useful for many actuation applications. Polypyrrole , is one of the most common conducting polymers of choice for the development of actuator technologies and has been well characterized in its mechanical, electrical, and electrochemical response. Although capable of producing almost 10 times more active stress for a given cross-sectional area than skeletal muscle, strains are relatively low on the order of 1 to 2 %, as are strain rates, which are on the order of a couple percent per second. Small strains can be amplified to produce large bending displacements by configuring the conducting polymer film in a trilayer configuration with two conducting polymer films sandwiching an electrolyte gel layer. This thesis focuses on the development of conducting polymer bending actuators in air. There is a strong correlation found between applied voltage, temperature, and the speed of actuation. Several experiments were carried out to determine the effect of temperature on the mechanical, electrical, and electrochemical properties of the components of the trilayer.; (cont.) This data coupled with thermal profiles of trilayers during actuation...
Conducting polymers are known to mechanically respond to electrochemical stimuli and have been utilized as linear actuators. To date, the most successful mechanism for actuation is ionic ingress and egress, though mechanisms based on conformational changes and molecular interactions have also been proposed. In the pursuit of new conducting polymer actuators it is necessary to design, synthesize, and characterize new materials, spanning scientific disciplines from synthetic chemistry to materials and mechanical engineering. As such, the topics of synthesis and characterization of new conducting polymers are discussed, highlighting developments in techniques and instrumentation. Actuation in poly(3,4-ethylenedioxythiophene), or PEDOT, and composites of PEDOT and carbon nanotubes is presented, demonstrating strains of 4.5% and strain rates of 0.2% per second with faster responses generated in carbon nanotube composites. Actuation in poly(3-hexylthiophene) is presented, demonstrating the observation of a novel actuation mechanism relating the potential of the polymer to the mechanical response. Further study of the actuation of polypyrrole at temperatures above 25°C is also discussed, in which response times decrease and magnitudes increase with temperature. Discrete time models of equivalent circuits and diffusion are utilized to predict conducting polymer actuator performance.; by Nathan A. Vandesteeg.; Thesis (Ph. D.)--Massachusetts Institute of Technology...
Interest in the use of conducting polymers as the active layer in electroluminescent devices has grown steadily over the last decade, and the commercialization of such devices is imminent. The stumbling block to the widespread adoption of conducting polymer based devices is their short lifetime due to the rapid photo-oxidation of the films under ambient conditions. Improved processing and encapsulation techniques have been studied extensively in an effort to reduce photo-oxidation of these devices, with limited success.
The pathway for photo-oxidation in conducting polymer films involves energy transfer from the polymer triplet exciton to triplet (ground state) oxygen in the film. The oxygen is excited to a highly reactive singlet state, which reacts with the conducting polymer backbone, resulting in the formation of luminescence-quenching defects. Since the triplet exciton drives this process, controlling the triplet exciton dynamics will slow the photo-oxidation process.
To control the triplet exciton dynamics in conducting polymer films, small concentrations of metal nanoshells are added. Metal nanoshells are composite particles consisting of a nanometer-scale dielectric core coated with a thin metal shell. The plasmon resonance of the metal nanoshells depends on the ratio of their core radius to shell thickness...
The objective of this paper is to identify a suitable coating material in order to tune the microwave radiation and produce absorption losses for Wi-Fi devices. It is also desirable to obtain high absorption losses outside the Wi-Fi microwave frequency range of 2.4 GHz. Literature reviews of several types of material are described and compared for the use of the selected material in order to coat a Wi-Fi device for the desired absorption losses for that device. The selected material for the Wi-Fi device is usually a metal material or a combination of metals like Aluminium in polymer matrix with different types of composites. The choice of materials will aim to target the tuning of the electromagnetic spectrum at a frequency in the range of 2.4 GHz. The paper focuses on two groups of polymer materials; conducting material as a result of composites like Carbon Nanotube Composites (CNC) or other metal composites. The second group is the Intrinsic Conducting Polymer (ICP) which conducts as a result of doping with other materials. A third group is the highly conductive metals like copper and aluminum. The metals are used as a reference comparator to the other two groups.; Whamid Al-Shabib, Daryoush Habibi, Zonghan Xie and Xiaoli Zhao
Conducting polymers are a subset of materials within the electroactive polymer class that exhibit active mechanical deformations. These deformations induce stresses and strains that allow for conducting polymers to be used as an actuator for mechanical devices. Incorporation of conducting polymer actuators into mechanical devices requires electrochemical and mechanical characterization of varying polymer sample sizes and their active properties. Of particular interest, is the characterization of macro-length polymer samples, which have yet to be investigated. An understanding of conducting polymer films and their feasibility as an actuator in a mechanical device are required for the development of a conducting polymer based rotary motor. The conducting polymer, polypyrrole, was studied for its feasibility as an actuator for control surfaces on autonomous underwater vehicles. Enhancements to the actuator's performance were addressed following the feasibility study. The development of an electrochemical dynamic mechanical analyzer provides an instrument for characterization of the polymer's properties over a variety of sample sizes and actuation conditions. Finally, the application of polypyrrole as an actuator and possible enhancements combined with the characterization of macro-length polymers provides the necessary tools to develop a rotary motor. Enhancements to polypyrrole actuators in this study account for an increase in tip force of 350% and a seven fold increase in achievable strain.; (cont.) Completion of a novel electrochemical dynamic mechanical analyzer...
The development of powerful and efficient artificial muscles that mimic Nature will profoundly affect engineering sciences including robotics and prosthetics, propulsion systems, and microelectromechanical systems (MEMS). Biological systems driven by muscle out-perform human-engineered systems in many key aspects. For example, muscle endows animals with a level of dexterity and speed that has yet to be emulated by even the most complex robotic system to date. Conducting polymers were chosen for research as actuators, based on a review of the relevant properties of all known actuators and active materials. Key features of conducting polymer actuators include low drive voltages (1 - 2 V) and high active strength (10 - 40 MPa) but moderate active strains (2 %). Active strains of 20 %, which human skeletal muscle is capable of, are desirable for applications in life-like robotics, artificial prostheses or medical devices. This thesis focuses on two approaches to create large contraction in conducting polymer actuators. The first strategy utilizes polypyrrole (PPy), a conducting polymer actuator material that contracts and expands based on a bulk ion swelling mechanism. Optimization of the polymer activation environment via room temperature ionic liquids enables PPy actuators to generate large contractions (16.3 % recoverable strain at 2.5 MPa...
Full-text version available Open Access at: http://www.cienciateca.com/SupercapPaniPmo12_Electrochem%20Comm_5_2003_149.pdf; Integration into a conducting polymer matrix to form a hybrid material is an effective way to harness the electrochemical activity of nanosized oxide clusters. By anchoring them into polyaniline, the reversible redox chemistry of the otherwise soluble polyoxometalate clusters can be combined with that of the conducting polymer and be put to work in energy storage applications. We present here preliminary results that show how the resulting hybrid polymer displays the combined activity of its organic and inorganic components to store and release charge in a solid state electrochemical capacitor device.; Partial financial support from the Ministry of Science and Technology (Spain) (Grants MAT2001-1709-C04-01 and MAT2002-04529-C03), and from the Domingo Martínez Foundation, as well as fellowships from the European Marie Curie Program (to M.C.), from the ministry of Education (Spain) (to J.A.A.) and from CONACYT (Mexico) (to K.C.G.) are gratefully acknowledged.
P.J.K. and M.C. appreciate partial support from State Committee for Scientific Research (KBN),
Poland (Grant 7 T09A 03120).; Peer reviewed