Polythiophene Films Research Articles

The use of polythiophene for mild steel protection

The synthesis of a polythiophene (PTh) film was achieved on polypyrrole (PPy) coated mild steel (MS) electrode. The synthesis of primary PPy coating was carried out from a monomer containing aqueous oxalic acid solution. Then, the synthesis of top PTh film was achieved in 0.1 M thiophene containing ACN–LiClO 4. Cyclic voltammetry technique was used for both syntheses. The corrosion behavior of PPy/PTh coated MS was investigated in 3.5% NaCl solution, by using anodic polarization, open circuit potential–time ( E ocp–t) curves and electrochemical impedance spectroscopy (EIS). It was shown that the coating has very low porosity and exhibited excellent barrier property against the attack of corrosive environment, for extensive periods. It was also able to provide anodic protection to MS and an efficiency value of 98.2% was calculated after 220 h of exposure time.

Electrochemical relaxation study of polythiophene as conducting polymer (I)

The electro synthesis of polythiophene film from 2,2′-bithiophene monomer was investigated using different electrochemical techniques. The stability and electrical conductivity of the prepared film were studied. The most stable polythiophene film which also show slow relaxation (lowest relaxation time) was obtained using a galvanostatic technique in acetonitrile solvent with TBAPF 6 as supporting electrolyte at 5 °C. As the donor number of the solvent increases, the relaxation time decreases. The relaxation time is also sharply affected by temperature.

Growth of novel polythiophene and polyphenyl films via surface polymerization by ion-assisted deposition.

Surface polymerization by ion-assisted deposition (SPIAD) is used here to grow novel polythiophene and polyphenyl thin films on a silicon surface by hyperthermal, mass-selected thiophene cations coincident with a thermal beam of alpha-terthiophene or p-terphenyl neutrals. X-ray photoelectron spectroscopy (XPS) observes a large enhancement in film growth for SPIAD compared with either thiophene ions or alpha-terthiophene exposure alone. Changes in S/Si and C/Si ratios from XPS, direct observation of higher polymerization products by mass spectrometry, characteristic vibrations in the Raman data, and enhanced stability in a vacuum all indicate that 200 eV SPIAD polythiophene films are most efficiently polymerized at a 1/150 ion/neutral ratio. Other ion/neutral ratios are less efficient at film growth, in the order 1/150 > 1/450 > 1/900 > direct ion deposition > 1/50. Changes in C/Si ratios and higher polymerization products indicate polymerization occurs in SPIAD polyphenyl films grown with a 1/100 ion/neutral ratio. Furthermore, thiophene ions are found to incorporate into some, but not all, of the polymerization products observed in mass spectrometry.

Anodic polymerization of aromatic compounds in centrifugal fields

Polyaniline (PANI), polythiophene (PT) and polypyrrole (PPy) films were electrochemically synthesized under centrifugal acceleration ranging 1–300 g. The polymerization rate of the studied monomers was found to be affected by the applied gravitational force. The polymers thus synthesized with and without centrifugation also exhibited clear differences in their physical and chemical properties. In addition, morphological structure of the polymer films was also affected by the centrifugal field. The effect of the force exerted on the working electrode was found to be anisotropic. A mechanism for the electrochemical deposition of the polymers under centrifugal force has also been proposed.

Electrochemical synthesis of polythiophene on nickel coated mild steel and corrosion performance

Electrochemical polymerization of polythiophene (PTh) was investigated on nickel coated mild steel (MS) electrode, in LiClO 4 containing acetonitrile medium (ACN-LiClO 4). Nickel layer (1 μm thick) was deposited galvanostatically, from a proper bath solution. Then, the synthesis of PTh film was achieved in 0.1 M thiophene containing ACN-LiClO 4, by using cyclic voltammetry technique. The corrosion performances of nickel coated samples with and without polymer top coats were investigated in 3.5% NaCl solution, by using electrochemical impedance spectroscopy (EIS) and anodic polarization curves. The nickel coating behaved like a physical barrier and provided some protection to MS against corrosion. But its barrier property diminished significantly with time and failed to protect MS. It was shown that PTh top coat improved the barrier efficiency remarkably, and excellent protection efficiency was obtained against MS corrosion, for considerable exposure time in such aggressive environment.

Optical and Chemical Properties of Polythiophene Films Produced via Surface Polymerization by Ion-Assisted Deposition

Polythiophene films are produced via surface polymerization by ion-assisted deposition (SPIAD), in which 55−200 eV thiophene ions and α-terthiophene (3T) neutrals are co-deposited on surfaces. These SPIAD polythiophene films display unique optical properties in their photoluminescence and UV/vis absorption compared with films prepared by either 3T or direct thiophene ion deposition only. The optical properties of SPIAD polythiophene depend on the deposited ion-to-neutral ratio and ion energy. Ion-to-neutral ratios of 1/100 cause a red shift in the photoluminescence of SPIAD films compared with 3T films whereas ratios of ∼1/400 cause a blue shift. Ion energies at 100 eV showed the most enhanced photoluminescence and UV/vis absorption compared with 3T films. Mass spectrometry indicates that a variety of higher molecular weight oligomers with some masses exceeding [3T]3 are formed by SPIAD. UV/vis spectra and X-ray photoelectron spectroscopy support the formation of a distribution of oligomers, while the lat...

Fabrication and Photoelectrochemical Properties of Polythiophene-Porphyrin Composite Films

Polythiophene-porphyrin composite films consisting of bithiophene and meso-tetrathienylporphyrin were prepared on transparent indium tin oxide (ITO) electrodes. First, a polythiophene film was fabricated on the ITO electrode by electrochemical polymerization in the bithiophene solution with repeated oxidation-reduction cycles in the 0–+2 V region. Then, porphyrin was assembled on the polythiophene-modified electrode by using the same electrochemical polymerization in the porphyrin solution, to give polythiophene-porphyrin modified electrodes. The amount of porphyrin increased with increasing number of scanning cycles for electrochemical polymerization. In the presence of oxygen, irradiation of the polythiophene-porphyrin modified electrodes resulted in stable cathodic photocurrents. Photocurrent increased with increasing amount of porphyrin. Large cathodic photocurrents were observed in the negatively applied potentials. The photocurrent action spectra of modified electrodes strongly suggested the photochemical cooperation of porphyrin and polythiophene for photocurrent generation. The combination of polythiophene and porphyrin in the electrochemically modified electrode is quite effective for generating large photocurrents.

Conducting polymer electrochemical actuator made of high-strength three-layered composite films of polythiophene and polypyrrole

Tri-layer conducting polymer composite films of polypyrrole/polythiophene/polypyrrole have been electrochemically synthesized by successive oxidation of pyrrole in aqueous solutions and thiophene in boron trifluoride diethyl ether (BFEE) solution, respectively. One of the polypyrrole layers was doped by a small anion of perchlorate (PPy (ClO 4)) and the other one was doped by a large anion, dodecylbenzene sulfonate (PPy (DBS)). The tri-layer film was deformed by electrochemical reduction and oxidation of polypyrrole layers. The polythiophene (PTh) layer provided a high strength conductive polymeric support for the actuator. A 0.4 mg composite film can reversibly raise a 10 mg material (e.g. a copper wire) from the position of 0° to the position of ∼±90° at ±1. 0 V (versus saturated calomel electrode (SCE)), respectively, while the bi-ionic film of PPy (ClO 4)/PPy (DBS) with the same weight can raise the 10 mg copper wire to only a position of ∼±25°. The movement rate of the tri-layer film was also higher than that of the bi-ionic polypyrrole film.

Oxygen-induced quenching of photoexcited states in polythiophene films

Oxygen-induced quenching of photoexcited states in polythiophene films

Oxygen-induced quenching of photoexcited states in polythiophene films

Oxygen causes reversible and irreversible detrimental effects to the performance of organic (opto-)electronic devices. In order to get some insight into the mechanisms of these effects, we investigated the kinetics of fluorescence quenching (FQ) in thin films (d≈100 nm–12 μm) of regioregular polyalkylthiophenes upon exposure to oxygen. The kinetics of FQ consists of a fast component, which is fully reversible, as well as a slow component, which is partially irreversible. The fast reversible component leads to a loss of fluorescence intensity of approximately 2% at an oxygen partial pressure of 1 bar within milliseconds. It is independent of the intensity of the exciting light and is ascribed to collisional quenching of excited singlet states after oxygen diffusion into the bulk of the film. The diffusion coefficients of oxygen and singlet excitons were determined as D(O2)=1.5(3)×10−7 cm2 s−1 and D(S1)=5×10−4 cm2 s−1, respectively. The slow reversible component, whose amplitude depends on light intensity, occurs on a time-scale of minutes. It is assigned to the formation of charge-transfer complexes between excited singlet states of polythiophene and oxygen. Femtosecond pump-probe experiments show that effective quenching of excited singlet states by oxygen takes place on a picosecond time-scale, leading to the enhanced formation of charged states.

A two-dimensional Raman spectroscopic study on the structural changes of a polythiophene film during the cooling process

Raman spectra of a polythiophene film measured over a temperature range 298–98 K were analyzed using generalized two-dimensional correlation spectroscopy. In the 1600–1250 cm−1 region, the asynchronicity of the bands indicates the existence of different species in the investigated polythiophene sample. At least four distinct bands at 1485, 1454, 1418, and 1360 cm−1 were identified. Among them, the band at 1454 cm−1, attributed to the neutral species of PTh, is found to be sensitive to the temperature-induced structural changes of the polythiophene film, while the bands of the oxidized species are less sensitive to the temperature change during the cooling process.

Redox Active p-Nitrophenyl Units bond to Electrodeposited Conducting Polythiophene Films

Two new thiophene derivatives bearing redox active p-nitrophenyl units were synthesized and electropolymerized to conducting polymers. It is found that not only the structure of monomer, but also the employed polymerization conditions have considerable effect on the electroactivity of the bonded redox groups of resulting polymer films. Depending on used conditions such as polymerization time, the polymerization of the same monomer could result in a polymer with well-defined redox transition of the nitrophenyl group or a polymer, in which the redox group is completely electrochemical inaccessible. Using designed experiments, we explained this phenomenon. These investigations provide further knowledge about the behaviors of redox group attached to electrode surface.

Electropolymerization of self-doped polythiophene in acetonitrile containing FSO 3H

Sulfonated polythiophene films were synthesized from the acetonitrile solution which contained different amounts of anhydrous fluorosulfonic acid (FSO 3H). Electrochemical oxidation of thiophene produced self-doped conducting polythiophene films which were soluble in DMSO and KOH. The solubility and conductivity properties of the polymer films were dependent on the degree of sulfonation (C/S ratio) value. The solubility values increased and conductivity values decreased with increasing degree of sulfonation (decreasing C/S ratio). The resulting polymer structures were characterized by cyclic voltammetry, UV-Vis, FT-IR, elemental analysis, dry conductivity, intrinsic viscosity measurement and thermal gravimetric analysis (TG).

Novel Fabrication of Conductive Polymers Contained Micro‐Array Gas Sensitive Films Using A Micromanipulation Method

AbstractA novel method for fabricating a micro gas sensor film on an indium tin oxide (ITO) electrode patterned using micro‐machining technology was developed. A micromanipulation system equipped with a counter electrode (Au; Ø10 μm) and a microsyringe, which was connected to a microinjection system, was first constructed. With this system, micro gas sensor arrays could be successfully prepared on ITO electrodes. Two kinds of micro gas sensor films were prepared, based on polythiophene (PTh) and poly(3‐n‐dodecylthiophene) (PD). The response behavior of conventional PTh and micro‐PTh films against NH3 at three different operating temperatures (25, 40 and 60 °C) was investigated by measuring the resistance of the film. With the micro‐PTh film, a reversible response was observed against NH3 when measured at 40 and 60 °C. In addition, the responsive characteristics of the microsensor films against different testing gases were examined at the three operating temperatures. The resistance of the microsensor films of PTh and PD changed considerably, depending on the type of testing gas, allowing these sensor films to be used for the detection of various gases. Furthermore, the microsensor films had a high stability compared with conventional films prepared from the same polymer.

A double-driven photoelectrochemical cell

A novel photoelectrochemical cell consisting of a set of organic thin films which generate photocurrents in opposite directions was fabricated. The polythiophene film containing 5,10,15,20-tetraphenylporphyrin ( TPP) and fullerene ( C 60 ) generated anodic photocurrents in the presence of ferrocene, while that containing TPP alone generated cathodic photocurrents under aerobic condition. The combination of these two film-modified electrodes showed a better cell performance than the simple sum of these two independent photoelectrochemical cells. A push–pull type, double-driven photoelectrochemical cell is proposed in this paper.

Comparison of different porous sol–gel matrices: template synthesis of polythiophene

Composite using polythiophene as the conducting polymer and different silica sol–gel as the host matrix were prepared by the template method. The electrochemical performance of the composites has been confirmed using cyclic voltammetry and was compared with the results obtained on polythiophene films synthetised under the same condition directly on ITO substrates. UV–Vis–NIR spectroscopy, scanning electron and atomic force microscopic measurements were done on all the different composites.

Comparative Study of Conducting Polymers by the ESCR Model

Following the hypothesis of the electrochemically stimulated conformational relaxation model (ESCRM), electrochemically generated films of poly(1-methylpyrrole), polythiophene, poly(3-methylthiophene), polyaniline, and polymethylaniline were studied by potential steps in lithium perchlorate/acetonitrile solutions. All the chronoamperograms studied by influence of different compaction potentials, or different temperatures, show a maximum, indicating the presence of conformational relaxation movements of the polymeric chains as kinetic-controlling processes of the electrochemical oxidation. Magnitudes as charge consumed to compact one mole of polymeric segments during cathodic polarization, the cathodic potential where the compaction of the polymers starts, the enthalpic increment between two stationary states defined by constant overpotentials of compaction and oxidation, and the diffusion constants stated at constant anodic overpotentials were obtained in the context pointed by the model for the studied p...

Coexistence of photoluminescence from two intrachain states in polythiophene films

Time-resolved photoluminescence (PL) measurements on highly ordered and disordered films of a polythiophene (PT) derivative were compared. Although delocalization lengths of $\ensuremath{\pi}$ electrons and the strengths of interchain interaction are quite different between the two films, a biexponential decay and a change in spectral shape, from one with a large 0-0 transition to one with a large 0-1 transition, were commonly observed. Therefore, we conclude that PL spectra of PT consist of two components having different spectral shapes and different lifetimes, and that these components originate from intrachain odd- and even-parity states that are coupled by electron-phonon interaction. This model explains the greatly reduced fluorescence yield for the ordered film as well as the time-resolved PL measurements.

Physical and electrochemical characterization of nanocomposites formed from polythiophene and titaniumdioxide

A simple method for covering titanium dioxide particles with a polythiophene film by chemical preparation was developed. The resulting nanocomposites consisted of a titanium dioxide core with a grain size of 25–250 nm and a polythiophene shell between 1 and 2 nm thickness. The composites were characterized by scanning electron microscopy, thermogravimetry, X-ray photoelectron spectroscopy, cyclovoltammetry, impedance spectroscopy and photocurrent spectroscopy. The content of polythiophene in the composite (determined by thermogravimetry), was between 2% and 5%. Disk-like electrodes were prepared by pressing and then characterized by various electrochemical methods. A reversible redox potential of the polythiophene of +1.0 V (NHE) was determined by cyclic voltammetry. The reduced form of polythiophene behaved as a p-type semiconductor so that the composite with n-type TiO 2 contained the properties of a p/n-junction. In the photocurrent spectra (depending on the applied potential), the characteristic anodic peaks of the TiO 2 at λ=320 nm and cathodic peaks of the polythiophene around λ=500 nm were found. A new cathodic peak observed at 370 nm was explained as a new feature of the pn interface.

Electrochemically synthesized polythiophene films with self‐organized microstructure

AbstractThe microstructure of electronically conducting polythiophene (Pth) films synthesized electrochemically was studied using a scanning electron microscope. A self‐organization phenomenon was observed in the films, which grew on a substrate with periodically arrayed holes of diameter less than 100 nm. Owing to the low bending stiffness and the high cohesive energy of nanowires, they combined in a self‐assembling manner into an interesting array of bundle shapes, each bundle having about 20–100 bonded nanowires. The physical mechanism of this phenomenon is elucidated using the theory of elastic buckling.