Thiophene Monomers Research Articles

Fabrication of bioanode by using electrically conducting polythiophene via entrapment technique

A glassy carbon electrode (GCE) was tailored with conducting polymer polythiophene and further immobilized by an enzyme glucose oxidase (GOx). A thin film of polymer was developed by electrochemical polymerization of thiophene monomer. During electrochemical polymerization of the monomer the enzyme GOx and the redox active mediator ferritin (Frt) were entrapped within this polymer matrix. In this novel approach, the entrapment of enzyme and mediators within a polymer matrix occurs without chemical reaction that could affect their activity. The entrapment of enzyme and mediator within the conducting polymer matrices increases the surface area of the electrode. The tailored GCE/Ptp/Frt/GOx electrode showed a high catalytic activity. The increased surface area causes a high rate of electron transfer between the electrode and Frt engaged as an electron transfer mediator. The electrochemical properties of the electrode were determined by cyclic voltammetry (CV) and linear sweep voltammetry (LSV). The fabricated bioanode showed a current density of 3.9mA cm−2 at 1.0 V vs. Ag/AgCl in a 45 mM glucose solution and suggests proficient chances in biofuel cells (BFCs) applications.

Synthesis of Soluble Ferrocene-Based Polythiophenes and Their Properties

Ferrocene-based polythiophenes are the promising class of the functional materials, but mostly the polythiophenes are insoluble in common solvents except some derivatives of polythiophenes like poly(3-hexylthiophene) (P3HT). Herein, two new ferrocene-based thiophene monomers, 2-(thiophen-3-yl) ethyl ferrocenoate and 2-(thiophen-3-yl) methyl ferrocenoate were synthesized and copolymerized with 3-hexylthiophene (3HT) respectively. The resulting polymers were soluble (in common organic solvents) and processable. The synthesis and the molecular weights were confirmed by the 1H-NMR and GPC studies respectively. Poly (TEF-co-3HT) was subjected to study the electrochemical properties in comparison of respective monomers and ferrocene. It was found that the resulting copolymer had the combined redox properties of its monomers. Also, very interestingly, the copolymer showed improved reversible redox properties which were not only better than its parent monomers but even better than the pure ferrocene. Photoemission spectra of P3HT and Poly (TEF-co-3HT) were also rerecorded and compared with each other.

Molecular doping of regioregular poly(3-hexylthiophene) layers by 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane investigated by infrared spectroscopy and electrical measurements

Molecular doping is a charge-transfer process intended to improve the performance of organic electronic devices such as organic transistors. We have investigated molecular doping of regioregular poly(3-hexylthiophene) (P3HT) layers by 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4-TCNQ) using infrared absorption spectroscopy in the multiple internal reflection geometry (MIR-IRAS) and conductivity measurements. IRAS data confirm that F4-TCNQ acts as an effective p-type dopant for P3HT; highly doped P3HT displayed an intense, broad absorption band due to polaron (“polaron band”) and a high carrier (hole) density which are indicative of the charge transfer between F4-TCNQ and P3HT. We demonstrate that the charge (hole) transferred from the dopant molecule is distributed along the P3HT polymer chain and spreads over at least 10 thiophene monomer units on the chain. From a comparison of the measured conductivity of F4-TCNQ-doped P3HT layers with the carrier density, we show that the carrier mobility is proportional to the concentration of carriers (holes), which suggests that F4-TCNQ doping induces the conformational change of P3HT polymer chains to enhance the mobility of holes in the films of the doped P3HTs.

Synthesis and characterization of all-conjugated hard-soft-hard ABA triblock copolythiophenes

A new thiophene monomer design was demonstrated by exploiting the flexibility and bulkiness of trisiloxane units to produce "soft" polythiophene materials. In practice, the thiophene monomer having trisiloxane units could be polymerized by Kumada Catalyst-Transfer Polymerization (KCTP) to afford well-defined poly(1,1,1,3,3,5,5-heptametyl-5-(6?-(thien-3?-yl)hexyl)trisiloxane-2?,5?-diyl) (P3SiHT) with low dispersity, which was viscous material with fluidity. To the best of our knowledge, it is first time to develop "liquid" polythiophene at room temperature. In addition, we are successful in synthesizing novel all-conjugated hard-soft-hard ABA triblock copolymer, where A and B were poly(3-hexylthiophene) (P3HT) and P3SiHT, respectively, based on KCTP method and sequential monomer addition technique. The livingness of the KCTP system was confirmed by size exclusion chromatography (SEC) UV traces. The formation of phase separated P3HT and P3SiHT domains in the triblock copolymer (P3HT-b-P3SiHT-b-P3HT) was supported by differential scanning calorimetry (DSC), although the existence of miscible domains was also implied.

Effect of Pth-Coated Li Powder Anode in Lithium Metal Batteries System

The Li metal anode is one of interested electrode which applied on the post-LIB (Li ion battery) system. However the dendrite growth on the Li surface made hard to commercialized Li metal anode battery. In this reason, we fabricated Li powder by Droplet Emulsion Technique (DET) and coated polythiophene (Pth) on the Li powder by polymerization method.[1] The thiophene monomer and FeCl3 was stirred in CHCl3 solution and polymerized by in situ on the surface of lithium powder.[2] This experiment formatted uniformly PTh layer on the Li powder surface. This Pth layer was helpful to suppressed the lithium dendrite growth when Li ion deposited on the Li powder (charge process). To fabricate the electrode Pth-coated lithium powder was placed on the stainless steel (SUS) mesh (15 Φ) and pressed 20 kg cm-2 regularly. Also the LiV3O8 (LVO) was used as cathode electrode because it is non-lithiated material. The cell was assembled in the coin type cell (CR2032) in Dry room. The morphology of lithium dendrite was observed by the FE-SEM, TEM and the coating layer was investigated by NMR and FT-IR. The conductivity of lithium powder anode and polythiophene-coated lithium powder was also measured by impedance analysis. All the cell were charged and discharged to 25% of the theoretical lithium capacity (965 mAhg-1) at 0.2 0.5, 1, 2 C-rate respectively. The result was analyzed EIS and CV. [1] Shin-Kook Kong, Bok-Ki Kim, Woo-Young Yoon, J. Electrochem. Soc, 159 9) A1551-A1553 (2012) [2] Haipeng Guo, Li Liu, Hong, Hong Shu, Xiukang Yang, Zhenhua Yang, Meng Zhou, Jinli Tan, Zichao Yan, Hai Hu, Xianyou Wang, J. Power Sources, 247 (2014) 117-126

Synthesis, characterization and optical properties of novel oligothiophenes bearing pyrene units attached via well defined oligo(ethylene glycol) spacers

Two new thiophene monomers bearing pyrene units attached via di(ethylene glycol) and tetra(ethylene glycol) spacers were synthesized, 3-methyl-4-(diethoxy) thiophene (M2) and 3-methyl-4-(tetraethoxy) thiophene (M4). These monomers were linked to thiophene and bithiophene via a Suzuki coupling reaction to give the corresponding terthiophenes and quaterthiophenes: [3,3-(di (diethoxypyrene)), 4,4′′′dimethyl–2,2: 5#14−15#-terthiophene (TT2)], [3,3-(di(tetraethoxypyrene)), 4,4′′′dimethyl–2,2:5#14−15#-terthiophene (TT4)], [3,3′′′-di(diethoxypyrene), 4,4′′′methyl-2,2′:5′: 2′′:5′′,2′′′-quaterthiophene (QT2)], and [3,3′′′-di(tetraethoxypyrene), 4,4′′′methyl -2,2′:5′:2′′:5′′,2′′′-quaterthiophene (QT4)]. The obtained oligothiophenes were characterized by 1H, 13C NMR spectroscopies and MALDI-TOF mass spectrometry. The optical properties of these compounds were studied by absorption and fluorescence spectroscopy. The absorption spectra of these compounds exhibited a broad absorption band at λmax=350nm arising from the S0→S2 transition of the pyrene group. This broadening is an indication of the presence of pyrene–pyrene interactions in the ground state. A discrete band at ca λ=385 due to the S0→S1 transition (n–π*) of the oligothiophene backbone was also observed. The emission spectra of oligomers TT2, TT4, QT2 and QT4 showed a “monomer emission” band at λM=379–450nm followed by an intense excimer emission band at λE=570nm due to intramolecular pyrene–pyrene interactions. The effect of the flexible spacer length as well as that of the oligomer backbone influences significantly the formation of pyrene–pyrene complexes.

Synthesis of Poly(3-hexylthiophene), Poly(3-hexylselenophene), and Poly(3-hexylselenophene-alt-3-hexylthiophene) by Direct C–H Arylation Polymerization via N-Heterocyclic Carbene Palladium Catalysts

Direct C–H arylation polymerization of 2-bromo-3-hexylselenophene and 2-bromo-3-hexylthiophene catalyzed by N-heterocyclic carbene (NHC) palladium-based and Pd(OAc)2-based systems has been carried out and investigated. Under the optimized conditions, high molecular weight poly(3-hexylthiohphene) (P3HT) (Mn = 26.9K g/mol) with high head-to-tail regioregularity (94%) can be obtained by using [1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene]chloro[3-phenylallyl]palladium(II) (Pd-IPr) as the catalyst. Pd-IPr exhibits a wide range of working temperatures from 70 to 140 °C and good catalytic reproducibility as a result of its high thermal stability. It was found that the presence of additional phosphine ligand, such as tris(o-methoxyphenyl)phosphine, can increase the polymerization efficiency in the Pd(OAc)2 system. This improvement is linked to the stability enhancement for the active species during the course of catalysis. For the first time, poly(3-hexylselenophene) (P3HS) was also obtained by direct-arylation polymerization in this research. The modest molecular weight is attributed to the poor solubility of P3HS in the used solvents. Density-functional-theory (DFT) calculations were performed to investigate the postulated reaction mechanisms for our catalytic systems. The experimental observations can thus be elucidated by the help of computation. Most significantly, a main-chain alternating and side-chain regioregular (RR = 94%) poly(3-hexylselenophene-alt-3-hexylthiophene) (Alt-P3HST) with high molecular weight (20.0K g/mol) was successfully synthesized via the Pd-IPr-catalyzed direct-arylation polymerization of a well-designed 2-bromo-3-hexyl-5-(3-hexylselenophen-2-yl)thiophene monomer. The molecular properties of the Alt-P3HST were characterized to compare with those of P3HT and P3HS. This research demonstrates in-depth investigation on the NHC-based palladium catalysts for the synthesis of conjugated polymers via direct C–H bond polymerization.

Binder Effects in SiO2- and Al2O3-Bound Zeolite ZSM-5-Based Extrudates as Studied by Microspectroscopy.

Microspectroscopic methods were explored to investigate binder effects occurring in ZSM‐5‐containing SiO2‐ and Al2O3‐bound millimetre‐sized extrudates. Using thiophene as a selective probe for Brønsted acidity, coupled with time‐resolved in situ UV/Vis and confocal fluorescence microspectroscopy, variations in reactivity and selectivity between the two distinct binder types were established. It was found that aluminium migration occurs in ZSM‐5‐containing Al2O3‐bound extrudates, forming additional Brønsted acid sites. These sites strongly influence the oligomer selectivity, favouring the formation of thiol‐like species (i.e., ring‐opened species) in contrast to higher oligomers, predominantly formed on SiO2‐bound ZSM‐5‐containing extrudates. Not only were the location and distribution of these oligomers visualised by 3 D analysis, it was also observed that more conjugated species appeared to grow off the surface of the zeolite ZSM‐5 crystals (containing less conjugated species) into the surrounding binder material. Furthermore, a higher binder content resulted in an increasing overall reactivity owing to the greater number of stored thiophene monomers available per Brønsted acid site.

Role of gadolinium(III) complex in improving thermal stability of polythiophene composite

AbstractThis paper involves the preparation of polythiophene (PTP) and its composite by the oxidative polymerisation method by using ferric chloride as an oxidant and thiophene monomer. The gadolinium( III) complex obtained by the refluxing technique was used as dopant in the PTP matrix. On the basis of the spectroscopic characterisation, seven-coordinate geometry is proposed for the complex. Conductance measurement confirms the non-selectrolyte nature of complex. The PTP and its composite were subjected to FTIR, X-ray diffraction and scanning electron microscope techniques. The powder X-ray diffraction pattern showed the high crystalline nature of the complex which in turn developed a good degree of crystallinity in the PTP composite. The average particle size was calculated as 4.655 ˚A and 3.737 ˚A for the dopant and PTP composite, respectively, by using Debye Scherrer’s equation. Thermal analysis was performed by thermogravimetric (TG) analysis, differential thermal analysis (DTA) and differential scanning calorimetry (DSC) techniques. The TG, DTA and DSC results were well-correlated. The thermal analysis revealed the high thermal stability of the dopant which in turn improved the thermal stability of the PTP composite, revealing the potential of the composite for high temperature applications.

Self-assembly and hybridization mechanisms of DNA with cationic polythiophene.

The combination of DNA and π-conjugated polyelectrolytes (CPEs) represents a promising approach to develop DNA hybridization biosensors, with potential applications for instance in the detection of DNA lesions and single-nucleotide polymorphisms. Here we exploit the remarkable optical properties of a cationic poly[3-(6'-(trimethylphosphonium)hexyl)thiophene-2,5-diyl] (CPT) to decipher the self-assembly of DNA and CPT. The ssDNA/CPT complexes have chiroptical signatures in the CPT absorption region that are strongly dependent on the DNA sequence, which we relate to differences in supramolecular interactions between the thiophene monomers and the various nucleobases. By studying DNA-DNA hybridization and melting processes on preformed ssDNA/CPT complexes, we observe sequence-dependent mechanisms that can yield DNA-condensed aggregates. Heating-cooling cycles show that non-equilibrium mixtures can form, noticeably depending on the working sequence of the hybridization experiment. These results are of high importance for the use of π-conjugated polyelectrolytes in DNA hybridization biosensors and in polyplexes.

Conductive polythiophene-like thin film synthesized using controlled plasma processes

Transparent conductive polythiophene-like thin films were synthesized by a plasma polymerization technique using a middle range frequency (40kHz). The effects of the variation of power and pressure on the chemical structure of the deposited film were investigated along with the effect of doping with iodine vapors on the conductivity of the films. Plasma polymerization is a low temperature process, provides deposition of thin polymer films on a wide variety of substrates, and has advantages due to non-involvement of any solvents. The chemical structure of the films was characterized using Fourier Transform Infrared Spectroscopy. The wetting properties of the films were studied using water contact angle measurements. The fragmentation of the thiophene monomer structure increased with increasing discharge power, implying that at low discharge power, the plasma phase was energy-deficient. The lower fragmentation of the monomer led to high retention of the monomer structure in the deposited films. Under various pressure conditions, the retention of the monomer structure was found to be similar as that of the deposited films. After doping with iodine vapor, a large conductivity enhancement, from 3.52×10−6 to 2.3×10−3s/cm was observed. The results showed the retention of a monomer structure having conjugated bonds in the films, responsible for the enhanced conductivities.

“Synthesis and characterization of novel luminescent polythiophenes containing pyrene units and oligo(ethylene glycol) spacers: Thermal and optical properties”

A novel pyrene containing thiophene monomer 3-methyl-4-(4-(pyren-1-yl)butoxy) thiophene was synthesized and fully characterized by FTIR and 1H and 13C NMR spectroscopies. This monomer was polymerized and copolymerized in the presence of 3-methyl-4-(tetraethoxy) thiophene, 3-hexylthiophene, 3-decylthiophene, and 3-dodecylthiophene using FeCl3 as oxidizing agent, to give the corresponding homopolymer HP3 and copolymers (CP1, CP2, CP3, CP4,CP5 and CP6). These polymers exhibited good thermal stability with T10 values between 312 and 414°C, and Tg values varying from −38 to 24°C. CP5 exhibited two absorption bands at 246 and 416nm whereas CP6 absorbed only at 242nm. The emission spectra of both polymers showed a monomer emission at 376–396 followed by an intense excimer emission at 570nm, which reveals the presence of intramolecular non parallel pyrene–pyrene interactions.

Steering Poly(thiophene) Properties by Incorporation of Phenyl Groups

In order to tune the optical properties of poly(3-alkylthiophene)s, varying amounts of phenyl groups were incorporated more or less randomly along the backbone of this polymer. Because a living random copolymerization of thiophene and phenyl monomers is not possible in standard conditions, a specially designed biaryl monomer was used. The degree of randomness of this incorporation could be estimated by an in-depth 1H NMR analysis. The effect on the bandgap was remarkable, since a linear relation between the bandgap and the percentage of introduced phenyl rings was observed. This enables the synthesis of conjugated polymers with tunable and predictable bandgaps. Aggregation and crystallization behavior were also affected by the introduction of phenyl rings. Aggregation was still possible with 20% of phenyl rings, albeit to a small extent, while crystallization was already completely inhibited at that point.

Tuning the morphology of electroactive polythiophene nano-structures

The self-assembly of thiophene monomers and the subsequent oxidative polymerization of them has been studied using the vapour phase polymerization (VPP) platform. A variety of nano-structures were obtained by varying the polymerization conditions with regard to temperature, time, addition of a secondary oxidant and crystal formation in the oxidant layer. The electrochemical and physical characterizations of these nano-structured polythiophene materials were performed using cyclic voltammetry, electron microscopy, UV–vis spectroscopy, conductivity, contact angle and BET surface area measurements. The presence of nano-structures indeed enhances the redox capacity and increases the active surface area compared to the analogue film without nanostructures. The hydrophobicity of the polymeric film is also tuneable from different nano-structures forming on top of the film.

Amperometric Simultaneous Measurement of Copper and Cobalt Ions with Polythiophene Incorporating Pendant Terpyridine Groups

Terpyridine containing thiophene monomer was synthesized. Electrochemical behavior of the monomer was studied by cyclic voltammetry. This monomer was polymerized via electrochemical methods and the resultant polymer was characterized. The stepwise fabrication process of the polymeric film electrode and its electrochemical sensing performance towards simultaneously Co and Cu ions were evaluated. The sensing parameters of the polymer electrode were investigated in detail, and the determination conditions were optimized. Under the optimal conditions, sensor response peak is linear to the Co ion concentration in the range of 1.0-50.0 µM and the Cu ion concentration in the range of 1.0–20.0 µM. Detection limit of terpyridine-based polythiophene film electrode for Co and Cu is respectively 100 nM and 0.05 nM.

Effects of catalyst loading amount on the synthesis of poly(3-hexylthiophene) via externally initiated Kumada catalyst-transfer polycondensation

A series of model polymerization are carried out via the one-pot externally initiated Kumada catalyst-transfer polycondensation (KCTP) of 2-bromo-5-chloromagnesium thiophene monomers, and the excess amount of initiators or catalysts are found no need to be isolated during the polycondensation process. Especially, the impacts of the nickel catalyst loading variation on regioregularity (rr), yield, molecular weight (M n), polydispersity (PDI) and initiation efficiency of poly(3-hexylthiophene) (P3HT) are systematically investigated. The 1H NMR, size-exclusion chromatography (SEC), and MALDI-TOF mass spectroscopy results indicated that an excess amount of catalyst does not influence yield, rr, M n, and PDI of P3HT, nor the initiation efficiency. However, the PDI of the product is broad, and the M n and rr values decreased in the absence of 1,3-bis (diphenylphosphino)propane (dppp). It can be concluded that the in-situ KCTP polymerization of P3HT is a practical and effective process. These results are especially valuable for the synthesis of all-conjugated block copolymers where macroinitiators are used.

Gradient copolymers of thiophene and pyrrole for photovoltaics

The electronic properties of copolymers can be tuned by controlling their monomer ratio, and therefore can potentially be used to improve charge separation in organic photovoltaic devices. Here we show evidence based on density functional theory calculations that it is possible to control the electronic structure of π-conjugated copolymers of thiophene and pyrrole to obtain a gradient in the band gap and both conduction and valence crystal orbital band levels by controlling their composition. Our calculations predict and optimal thiophene monomer fraction range between zero and 40% is needed in order to obtain the largest electronic structure gradients.

Modified porous silicon for electrochemical sensor of para-nitrophenol

Abstract Hybrid structures based on polythiophene modified porous silicon was used for the electrochemical detection of para-nitrophenol, which is a toxic derivative of parathion insecticide and it is considered as a major toxic pollutant. The porous silicon was prepared by anodic etching in hydrofluodic acid. Polythiophene films were then grown by electropolymerisation of thiophene monomer on three different surfaces: hydrogenated PSi, oxidized PSi and amine-terminated PSi. The morphology of the obtained structures were observed by scanning electron microscopy and characterized by spectroscopy (FTIR). Cyclic voltammetry was used to study the electrochemical response of proposed structures to para-nitrophenol. The results show a high sensitivity of the sensor and a linearity of the electrochemical response in a large concentration interval ranging from 1.5 × 10−8 M to the 3 × 10−4M.

Synthesis, Characterization and Electrical Conductivity of Zinc Oxide Nanoparticles Embedded in Polythiophene Nanocomposites

Polythiophene/ZnO (PTh/ZnO) nanocomposites composed of conducting polymer PTh were prepared by chemical polymerization of thiophene monomer using FeCl3 as an oxidant and ZnO nanoparticles by reverse micellar method. The nanocomposites were also characterized using FTIR, SEM, TEM, and XRD. It was found that the electrical conductivity of the nanocomposites first increased conductivity of the nanocomposite first increased but later on decreased as the temperature increased. Electrical conductivity of nanocomposite containing polymer matrices and zinc oxide nanoparticles showed good stability in terms of electrical conductivity retention up to 110 � C. Scanning electron micrographs showed globular particles and the presence of clusters of composite particles. Transmission electron micrographic (TEM) analyses revealed the particle size of the composite to be in the range 22–17 nm. Thermal analyses (TG/DTA) revealed the outstanding stability of PTP–ZnO composites compared to PTP. The conductivity of PTP and of PTP–ZnO composite was of the order of 10 −4 –10 −2 Sc m −1 .

Optoelectronic properties of polythiophene thin films and organic TFTs fabricated by oxidative chemical vapor deposition

Fabrication of devices utilizing unsubstituted polythiophene (PT) has received limited attention because thin films of this insoluble material have been difficult to prepare using traditional solution-based methods. However, since the thiophene monomer is volatile, PT films can be readily fabricated by oxidative chemical vapor deposition (oCVD). The pressure of the oCVD process is here shown to significantly affect the optoelectronic properties of the PT films. Shifts in the Raman bands near 1500 cm−1 suggest that the lowest pressure deposition conditions (1 mTorr) result in shorter conjugation. Additionally, relative Raman peak intensities suggest that the polymer chains in these films contain more distortions than films deposited at higher pressures. UV-Vis absorption spectra of the oCVD PT films show that films deposited at the lowest pressure considered (1 mTorr) are slightly blue-shifted and demonstrate lower absorption than films deposited at higher pressures. PT films deposited at 75, 150, and 300 mTorr demonstrated similar UV-Vis absorption spectra, with absorption maxima near 515 nm. Organic thin film transistors (TFTs) were fabricated using oCVD PT as the active channel layer to analyze the effect of deposition pressure on charge transport and electrical properties. Films deposited at 150 mTorr demonstrate the greatest field effect carrier mobility of 4 × 10−3 cm2 V−1 s−1.