Conducting Copolymer Films Research Articles

Electrodeposited Copolymer Films with Tunable Conductivity

Conducting copolymer films were prepared from pyrrole (Py) and 1,12-di-(1-pyrrolyl) dodecane (DiPy) in an attempt to prepare conducting films that can be used as sensitive material of chemiresistor gas sensors. Copolymer thin films were obtained by electrochemical oxidation in a lithium perchlorate/acetonitrile electrolyte with different feed ratios of comonomers. Increasing the portion of DiPy in the comonomer mixture resulted in the formation of thinner and less rough copolymer films and to a modification of their morphology from a granular structure to a clover-like structure. In addition, copolymer films with very different conductivities were obtained by varying the comonomers ratio. Indeed, the conductivity of the copolymer containing 91% of Py was 2 × 105 times higher than the conductivity of the polymer containing 91% of DiPy, indicating that it is possible to tune the conductivity of the film by varying the composition of the initial comonomer mixture.

Conductive polymeric biomaterials for tissue regeneration applications

Tissue engineering involves materials science, bioengineering, and regenerative medicine and many other disciplines. In the early stage, it aims to develop functional biological alternatives that improve, or maintain the function of lost or damaged tissue by combining the scaffold, cells, and biological molecules (such as growth factors). In addition, the ultimate goal of tissue engineering is to regenerate or repair damaged tissues with the help of the biological substitutes. Therefore, the tissue engineering scaffold should mimic the property, structure of the damaged tissue and mimic the extracellular matrix to support cell survival and growth to improve the tissue function. Moreover, the scaffold should also enhance cell proliferation and guide differentiation to regenerate or repair damaged tissues. Over the years, numerous studies have demonstrated that electrical signals can influence cellular behavior and function and conductive materials can enhance cell proliferation and guide differentiation of stem cells through promoting intercellular signaling. Traditional polymers have good process property, biodegradability, and good biocompatibility. So they are most widely used in tissue engineering, but traditional polymers are insulators, which cannot respond to signal transmission between cells to further control cellular activities, such as cell proliferation, migration and differentiation. However, researchers have discovered a variety of electrically conducting polymers in recent decades, such as polyaniline (PANi), polypyrrole (PPy), polythiophene, and their derivatives (mainly aniline oligomers and poly(3,4-ethylenedioxythiophene)) which have good biocompatibility and excellent electrical conductivity. They have been widely used in biomedical fields including drug delivery systems, biosensors, neural implants, and biological actuator, mostly used in the field of tissue engineering scaffolds. Moreover, their excellent electrical conductivity can promote cell adhesion and proliferation at the interface between the polymer and tissue by electrical stimulation, thereby promoting tissue growth. Therefore, the field of tissue engineering by conductive polymeric biomaterials has received more and more attention. However, the pure conductive polymers are brittle and their poor processability limits their applications in tissue engineering. Therefore, composite conductive polymeric biomaterials have been developed based on the above-mentioned conductive polymers and biocompatible degradable polymers, which have excellent biocompatibility, electrical conductivity, and processability. This review will summarize a variety of composite conductive polymeric biomaterials used in tissue engineering, such as pure conducting polymers, conducting blends or composite films, conducting copolymer films, conducting nanofibers, conducting hydrogels, and conducting composite three-dimensional (3D) scaffolds. In addition, recent research in tissue engineering has found that these conductive polymeric biomaterials can be used in various electrical signal sensitive tissues engineering including bone, muscle, nerve and cardiac tissue engineering. The above aspects will be discussed in detail in this paper.

Poly(3,4-ethylenedioxythiophene) Bearing Phosphorylcholine Groups for Metal-Free, Antibody-Free, and Low-Impedance Biosensors Specific for C-Reactive Protein.

Conducting polymers possessing biorecognition elements are essential for developing electrical biosensors sensitive and specific to clinically relevant biomolecules. We developed a new 3,4-ethylenedioxythiophene (EDOT) derivative bearing a zwitterionic phosphorylcholine group via a facile synthesis through the Michael-type addition thiol-ene "click" reaction for the detection of an acute-phase biomarker human C-reactive protein (CRP). The phosphorylcholine group, a major headgroup in phospholipid, which is the main constituent of plasma membrane, was also expected to resist nonspecific adsorption of other proteins at the electrode/solution interface. The biomimetic EDOT derivative was randomly copolymerized with EDOT, via an electropolymerization technique with a dopant sodium perchlorate, onto a glassy carbon electrode to make the synthesized polymer film both conductive and target-responsive. The conducting copolymer films were characterized by cyclic voltammetry, scanning electron microscopy, attenuated total reflection Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and electrochemical impedance spectroscopy. The specific interaction of CRP with phosphorylcholine in a calcium-containing buffer solution was determined by differential pulse voltammetry, which measures the altered redox reaction between the indicators ferricyanide/ferrocyanide as a result of the binding event. The conducting polymer-based protein sensor achieved a limit of detection of 37 nM with a dynamic range of 10-160 nM, covering the dynamically changing CRP levels in circulation during the acute phase. The results will enable the development of metal-free, antibody-free, and low-impedance electrochemical biosensors for the screening of nonspecific biomarkers of inflammation and infection.

Small-Area, Resistive Volatile Organic Compound (VOC) Sensors Using Metal-Polymer Hybrid Film Based on Oxidative Chemical Vapor Deposition (oCVD).

We report a novel room temperature methanol sensor comprised of gold nanoparticles covalently attached to the surface of conducting copolymer films. The copolymer films are synthesized by oxidative chemical vapor deposition (oCVD), allowing substrate-independent deposition, good polymer conductivity and stability. Two different oCVD copolymers are examined: poly(3,4-ethylenedioxythiophene-co-thiophene-3-aceticacid)[poly(EDOT-co-TAA)] and poly(3,4-ehylenedioxythiophene-co-thiophene-3-ethanol)[poly(EDOT-co-3-TE)]. Covalent attachment of gold nanoparticles to the functional groups of the oCVD films results in a hybrid system with efficient sensing response to methanol. The response of the poly(EDOT-co-TAA)/Au devices is found to be superior to that of the other copolymer, confirming the importance of the linker molecules (4-aminothiophenol) in the sensing behavior. Selectivity of the sensor to methanol over n-pentane, acetone, and toluene is demonstrated. Direct fabrication on a printed circuit board (PCB) is achieved, resulting in an improved electrical contact of the organic resistor to the metal circuitry and thus enhanced sensing properties. The simplicity and low fabrication cost of the resistive element, mild working temperature, together with its compatibility with PCB substrates pave the way for its straightforward integration into electronic devices, such as wireless sensor networks.

Possible tuning fabrication of nanoplatinum particles with the conducting copolymer films and their behavior toward the electrooxidation of methanol

AbstractThe electrocopolymerization of o‐toluidine (OT) and p‐phenylenediamine (PPDA) on a platinum electrode in a solution of 0.5 mol/dm3 H2SO4 with cyclic voltammetry was examined. The addition of PPDA to the solution of OT in 0.5 mol/dm3 H2SO4 accelerated the electrocopolymerization of OT and PPDA. Fourier transform infrared spectroscopy and ultraviolet–visible spectra for the polymers showed that the unit of PPDA should have been integrated into the backbones of the copolymers to form phenazine‐like ring structures, and the delocalization of electrons in the copolymer was better than that in poly(o‐toluidine) (POT). The scanning electron microscopy (SEM) images for the polymers showed that the copolymers became more porous, and smaller particles, which made oxygen, oxidized the reduced copolymer more easily and faster. It was proven with SEM, energy‐dispersive X‐ray spectroscopy, and transmission electron microscopy that the size of the nanoplatinum particles deposited on the copolymer reached 10 nm and was much smaller than those on POT. They had better tolerance to the poisoning species arising from the intermediates of the dissociation of methanol on a platinum electrode during the electrocatalytic oxidation of methanol. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Metal chelation and spatial profiling of components in crown ether functionalised conducting copolymer films

Crown ether functionalised conducting polymer films were used to complex barium ions from acetonitrile solution. It was found that fully-functionalised N-derivatized polypyrrole films do not possess adequate mechanical stability, but dilution with unfunctionalised bithiophene co-monomer leads to a series of copolymer films with excellent stability. Film reactivity, composition and structure were investigated using electrochemical, nanogravimetric, FTIR, XPS and neutron reflectivity techniques. The first three of these provided spatially integrated barium populations and neutron reflectivity provided spatially resolved compositional profiles. Measurements at various stages of film fabrication yielded spatial distributions of co-monomer, crown ether, solvent and barium (as perchlorate) components. Critically, the amount of free volume to accommodate crown motifs and barium within the film was limited by the film's internal microstructure and solvent content; the low solvent volume fraction creates a different local environment to solution.

Influence of reaction conditions on the formation of nanotubes/nanoparticles of polyaniline in the presence of 1‐amino‐2‐naphthol‐4‐sulfonic acid and applications as electrostatic charge dissipation material

AbstractBACKGROUND: Poly(1‐amino‐2‐naphthol‐4‐sulfonic acid) and its copolymers with aniline are a new class of conducting polymers which can acquire intrinsic protonic doping ability, leading to the formation of highly soluble self‐doped homopolymers and copolymers. Free OH and NH2 groups in the polymer chain can combine with other functional groups that could be present in protective paints which can thus be successfully used as antistatic materials.RESULTS: This paper reports the formation of nanotubes of polyaniline on carrying out oxidative polymerization of aniline in the presence of 1‐amino‐2‐naphthol‐4‐sulfonic acid (ANSA) in p‐toluenesulfonic acid (PTSA) as an external dopant. The presence of SO3H groups in the ANSA comonomer allows the copolymer to acquire intrinsic protonic doping ability. The polymerization mechanism was investigated by analysing the 1H NMR, 13C NMR, Fourier transform infrared and X‐ray photoelectron spectra of the copolymers and homopolymers, which revealed the involvement of OH/NH2 in the reaction mechanism. Scanning and transmission electron microscopy showed how the reaction route and the presence of a dopant can affect the morphology and size of the polymers. Static decay time measurements were also carried out on conducting copolymer films prepared by blending of 1 wt% of copolymers of ANSA and aniline with low‐density polyethylene (LDPE) which showed a static decay time of 0.1 to 0.31 s on dissipating a charge from 5000 to 500 V.CONCLUSION: Copolymers of ANSA with aniline were synthesized in different reaction media, leading to the formation of nanotubes and nanoparticles of copolymer. Blends of 1 wt% of PTSA‐ and self‐doped copolymers of ANSA and aniline with LDPE can be formulated into films with effective antistatic properties. Copyright © 2009 Society of Chemical Industry

Novel Strategies for the Deposition of COOH Functionalized Conducting Copolymer Films and the Assembly of Inorganic Nanoparticles on Conducting Polymer Platforms

AbstractA method for the preparation of COOH functionalized conducting copolymer films; toward the ultimate goal of developing resistance‐based sensing platforms, is presented. The method involved vapor phase copolymerization of pyrrole with a monomer containing the COOH functionality, thiophene‐3‐acetic acid (TAA). This copolymerization strategy aided in avoiding the need to employ brittle poly(thiophene‐3‐acetic acid) (PTAA) films in sensing applications. In this strategy, variation in the gas phase feed ratio of pyrrole to TAA allowed for the variation of the composition of the copolymer film and further allowed for the variation of both the conductivity and the amount of COOH functionality in the films. Further, the effect of covalent attachment of silver on the conductivity of the copolymer films is performed and presented. This covalent attachment of silver served the dual purpose of verifying the presence of active COOH groups on the surface, and also allowed for the quantification of the change in conductivity as a result of such attachment. Use of the conjugated ring containing 4‐aminothiophenol as the linker material enhanced the conductivities of the films. In contrast, employing cysteamine to link silver nanoparticles to the copolymer films did not result in any enhancement in the conductivities. An enhancement in the conductivities, ranging from 2 to 1000 times, is observed on covalent attachment of silver nanoparticles to the copolymer films using 4‐aminothiophenol as the linker material. This increase depended on the amount of TAA in the films and increased with increasing concentrations of TAA in the films. These results clearly indicate the use of these copolymer films in resistance‐based sensing. Further, this covalent attachment could be used as a novel strategy to integrate other inorganic nanomaterials on conducting polymer platforms.

Immobilization of glucose oxidase onto electrochemically prepared poly(aniline‐co‐fluoroaniline) films

Poly(aniline-co-fluoroaniline) [poly(An-FAn)] films were electrochemically deposited on indium tin oxide glass plates. The characterization of these conducting copolymer films was carried out with ultraviolet–visible and Fourier transform infrared techniques. The enzyme glucose oxidase (GOX) was immobilized onto the conducting poly(An-FAn) films by a physical adsorption method. Amperometric response experiments carried out with poly(An-FAn)/GOX films revealed linearity from 0.5 to 22 mM glucose, and the Michaelis–Menten constant was found to be about 23.5 mM. The shelf life of these poly(An-FAn)/GOX electrodes was measured to be about 15 days, and the electrodes were stable up to 45°C. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3999–4006, 2004

Immobilization of glucose oxidase onto electrochemically prepared poly(aniline‐co‐fluoroaniline) films

AbstractPoly(aniline‐co‐fluoroaniline) [poly(An‐FAn)] films were electrochemically deposited on indium tin oxide glass plates. The characterization of these conducting copolymer films was carried out with ultraviolet–visible and Fourier transform infrared techniques. The enzyme glucose oxidase (GOX) was immobilized onto the conducting poly(An‐FAn) films by a physical adsorption method. Amperometric response experiments carried out with poly(An‐FAn)/GOX films revealed linearity from 0.5 to 22 mM glucose, and the Michaelis–Menten constant was found to be about 23.5 mM. The shelf life of these poly(An‐FAn)/GOX electrodes was measured to be about 15 days, and the electrodes were stable up to 45°C. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3999–4006, 2004

Electrosynthesis and characterization of new conducting copolymer films from 1-naphthol and methyl naphthyl ether

New conducting polymer films have been prepared on platinum electrodes by anodic polymerization of 1-naphthol in the presence of methyl naphthyl ether (MNE) in MeCN containing 0.1 M LiClO4. The presence of MNE was found to suppress oligomer formation and significantly affect the physicochemical properties of the polymeric films formed via copolymerization, as confirmed by IR and elemental analysis. In contrast to the autocatalytic polymerization mechanism observed during poly(1-naphthol) formation, a competitive catalytic-inhibiting mechanism was found for the copolymer. The copolymer (1:1 and 1:10 1-naphthol:MNE) showed electrochemical activity similar to that of poly(1-naphthol). The copolymer films resisted degradation in MeCN effectively and charging–discharging cycles led to doubling of the redox charge after about 20 cycles, while poly(1-naphthol) films lost 90% of the redox charge under the same conditions. The conductivity of copolymer (1:1) films were 1–2 orders of magnitude lower than that of poly(1-naphthol). The diffusion coefficients of the charge transfer for the doping–dedoping processes of the copolymer films were slightly lower than for poly(1-naphthol), but the diffusion coefficients for the redox [Fe(CN)6]3−/4− were comparable for both films. © 2000 Society of Chemical Industry

The electrochromic response of polyaniline and its copolymeric systems

Conducting polyaniline (PANI) and its copolymer films of poly(aniline-co- o-toluidine) (PAOT) and poly(aniline-co- o-anisidine) (PAOA) have been electrochemically synthesized. The optical and structural properties of PANI, PAOT and PAOA have been studied using UV-visible absorption and X-ray diffraction techniques. The X-ray diffraction study reveals a crystalline structure for PANI whereas it shows an amorphous structure for PAOT and PAOA conducting copolymer films. Moreover, the switching lifetime, applied voltage, cycle lifetime in the glass/ITO/conducting polymer/HCl/ITO/glass configuration of PANI, PAOA and PAOT have been experimentally investigated. Further, the current transient for coloration and discoloration has been analysed in order to understand the charge transport in conducting polymer and copolymeric systems. It has been shown that PAOA shows better electrochromic response (143 ms) than PANI and PAOT systems. It is believed that the presence of the -OCH 3 group in the PAOA copolymer facilitates the torsional angle between aniline and methoxy aniline. In addition, the effect of HCl acid molarity on the switching response of PAOA conducting copolymer films has been studied.

Preparation and characterization of conducting copolymer films from 5-aminoquinoline and aniline

Conducting copolymer films from 5-aminoquinoline and aniline (abbreviated PAq-An) were prepared by anodic polymerization of different molar ratios of the corresponding monomers in MeCN using cyclic voltammetry and potential step methods. Ellipsometric measurements on the different copolymers indicated that the thickness increases linearly with the anodic charge but with different efficiencies. The electroactivity of the copolymers is attributed to polyaniline in the films and increases as the ratio of aniline in the polymerization solution increases. The copolymer PAq-An(1:5) shows even better electroactivity than polyaniline films prepared under the same conditions due to the higher polymerization efficiency and stability of the former films. Analysis of the spectroelectrochemical measurements in acid solutions showed that the redox peaks of the copolymer PAq-An(1:5) are composed of two consecutive redox processes. Models for the redox processes are proposed to analyse the spectroelectrochemical transient behaviour of the copolymer.

Synthesis, electrochemistry, and ligand substitution reactions of conducting copolymer films of ruthenium polypyridine complexes and aromatic heterocycles

Conducting films containing ruthenium complexes of the general formula [Ru(2,2′-bipyridine)2(pmp)X]2+ (pmp = 3-(pyrrol-1-ylmethyl)pyridine, X = Cl−, ClO4−, pmp, CH3CN, or H2O) have been prepared by copolymerization of the Ru complex monomer with pyrrole, 3-methylthiophene, 1-methyl-3-(pyrrol-1-ylmethyl)pyridinium(1+), or 2,2′-bithiophene. The immobilized complexes exhibit rapid and reversible electrochemistry in acetonitrile. The perchlorate and water ligands are rapidly substituted to give the acetonitrile complex, while the chloride ligand is replaced more slowly. In aqueous media, both the perchlorate complex and chloride yield an aqua complex. The substitution rate of the chloride ligand is again low but is enhanced by photolysis. No substitution reactions were observed for the acetonitrile or pmp ligands under a variety of conditions tested. Infrared spectroscopy and fast atom bombardment mass spectroscopy indicate that attempts to isolate [Ru(bp)2(pmp)(ClO4)]+ as a solid in fact give the aqua complex. The perchlorate complex may also rearrange to the aqua complex in polymer films. Films containing the aqua complex were not useful for electrocatalytic oxidation because of the instability of the conducting polymer matrix at low pH and the inactivity of the complex at higher pH values. Key words: polythiophene, polypyrrole, electropolymerization, metallopolymer.

Conducting polypyrrole films containing [Ru(2,2'-bipyridine) 2(3-{pyrrol-1-ylmethyl} pyridine)Cl] +: Electrochemistry, spectroelectrochemistry, electronic conductivity, and ionic conductivity

Electronically conducting copolymer films of pyrrole and [Ru(bp) 2(pmp)Cl] + (bp = 2,2'-bipyridine, pmp = 3-(pyrrol-1-ylmethyl)pyridine) have been prepared by anodic polymerization. Voltammograms of these copolymer films exhibit reversible electrochemistry of the Ru complex at a formal potential of +0.82 5 V vs. SSCE, superimposed on a broad flat wave due to the polypyrrole backbone. The electrochemistry of the polypyrrole backbone is similar to that of polypyrrole films grown under similar conditions. The Ru content of the films, which has been estimated by cyclic voltammetry and by visible region spectroelectrochemistry, can be increased both by increasing the [Ru(bp) 2(pmp)Cl] +: pyrrole ratio in the polymerization solution and by increasing the polymerization potential. The electron and ion transport properties of films prepared under a variety of conditions have been measured in order to assess the potential value of copolymers of this type in electrocatalysis. The incorporation of the Ru complex into polypyrrole increases its ionic conductivity but decreases its electronic conductivity. However, the conditions required for incorporating a significant quantity of the Ru complex, produce a polypyrrole matrix with less than optimal transport properties.