Polythiophene Backbone Research Articles

Conductive characteristics of radical‐bearing polythiophenes using a microcomb‐shaped electrode

AbstractThe electric conductivity of π‐conjugated and radical‐bearing polymers, i.e., polythiophenes bearing pendant galvinoxyl and phenoxyl radical groups, was measured using a microcomb‐shaped electrode. The electric conductivity was found to be enhanced by the radical content in the polymer. The infrared (IR) and Raman spectroscopies suggested a structural change from an aromatic form to a quinoid one in the polythiophene backbone by the phenoxyl radical generation. The effect of the pendant galvinoxyl radical's unpaired electron on the electric conductivity of the polythiophene was discussed by comparing the conductivity of a radical‐bearing polystyrene and a polythiophene mixed with low‐molecular radical molecules. Copyright © 2007 John Wiley & Sons, Ltd.

Electrosynthesis of a functional conducting polymer incorporating ferrocene unit from an EDOT-based bithiophenic precursor

Abstract A precursor of electrogenerated functional polythiophene combining an EDOT moiety with a thiophene ring on which a ferrocene group is attached at the internal β-position via a sulphide linkage (1) has been synthesized and characterized. The electrochemical polymerization of this precursor has been investigated in potentiodynamic and potentiostatic conditions. The analysis of the electrochemical behavior of the films growth under various conditions shows that potentiostatic polymerization of 1 in nitrobenzene leads to a polymer which exhibit the electroactivity of the polythiophene backbone and that of the attached ferrocene moiety.

Novel Brush-Type Copolymers Bearing Thiophene Backbone and Side Chain Quinoline Blocks. Synthesis and Their Use as a Compatibilizer in Thiophene−Quinoline Polymer Blends

New copolymers bearing different degree of grafted polyquinoline segments onto a polythiophene backbone were obtained via atom transfer radical polymerization of a vinyl quinoline monomer using a properly modified polythiophene backbone as macroinitiator. The initiator preparation was based on the bromination to a certain extent of a commercially available poly(3-hexylthiophene-2,5-diyl) (P3HT) and subsequent conversion of the bromine groups to proper propionyl bromide units through a three-step process. Polymerization of the vinyl quinoline monomer, using typical ATRP conditions, resulted in the desired copolymers, which were effectively characterized using 1H NMR, UV−vis, and luminescence spectroscopy, as well as cyclic voltammetry. These copolymers were used in order to study their compatibilization efficiency in an immiscible P3HT/polyquinoline blend, which has been tested previously with respect to its photovoltaic efficiency. A detailed morphology study using atomic force microscopy (AFM) has shown that nanophase separated systems were obtained and the domain size was dependent on the blend composition, as well as the copolymer grafting density.

Synthesis and characterization of chiral polythiophenes: Poly [( R)-(−) and ( S)-(+)-2-(3′-thienyl)ethyl N-(3″,5″-dinitrobenzoyl)-α-phenylglycinate

( R)-(−) ( 1) and ( S)-(+)-2-(3′-Thienyl)ethyl N-(3″,5″-dinitrobenzoyl)-α-phenylglycinate ( 2) monomers were synthesized, characterized, and polymerized in chloroform using FeCl 3 as an oxidizing agent. Molecular weights of 2.6 × 10 4 and 3.2 × 10 4 for poly1 and poly2, respectively, were determined by SEC analysis. FTIR spectra of the polymers indicated the coupling of monomers through the α positions. UV–vis spectra showed absorption bands at λ max = 226 and 423 nm for poly1 and poly2, ascribed to transitions of side groups and polythiophene backbone, respectively. Poly1 and poly2 remained stable up to 210 °C. At higher temperatures, a two step weight loss degradation process was observed for both polymers by TGA analysis. 1H NMR, in the presence of Eu(tfc) 3 , and optical rotation measurements indicate the chiral properties of the monomers 1 ([α] D 28 = −76.2) and 2 ([α] D 28 = +76.0), and the maintenance of chirality after polymerization ( poly1 [α] D 28 = −29.0 and poly2 [α] D 28 = +28.4, c = 2.5 in THF). According to scanning electron microscopic analysis, the polymers are highly porous.

Long-Lived Photoinduced Charges in Donor−Acceptor Anthraquinone-Substituted Thiophene Copolymers

The photoinduced charge-transfer properties of a series of polyalkylthiophene copolymers, carrying anthraquinone substituents covalently linked to the conjugated backbone, have been studied in the solid state by photoinduced absorption (PA) and light-induced electron spin resonance (LESR) spectroscopy. The measurements indicate the formation of metastable charges arising from the photoinduced electron transfer from the polythiophene backbone to the anthraquinone moieties. At low temperatures (below 200 K), long-lived persistent charges are formed, exhibiting lifetimes that extend for several minutes; their recombination kinetics has been studied by following the formation and decay of the PA and LESR signals. The results are rationalized using a model originally proposed to describe the low-temperature recombination kinetics of long-lived photoexcited carriers in amorphous inorganic semiconductors. It is clearly evidenced that, in these polymers, the number of acceptor substituents in the chain, easily tuned by chemical tailoring, plays a key role in the photoexcitation scenario.

Stable Superhydrophobic and Lipophobic Conjugated Polymers Films

With a view to developing repellent materials combining both low surface energy and rough structure, original semi-fluorinated polythiophenes have been chemically and electrochemically synthesized and characterized by cyclic voltammetry, GPC, and UV-visible measurements. Polymer films have been deposited onto different substrates by drop casting a soluble polymer fraction on glass plate or by electrodeposition on ITO plate. Surface properties and particularly water and oil repellencies have been investigated by goniometry and correlated with the surface morphology and structure observed by SEM. The incorporation of fluorocarbon chains in the rigid polythiophene backbone yields very low surface free energy materials. Moreover, the way of deposition has a huge influence on the quality and performance of the film surface properties. Electroformed polymers, due to rough surfaces, exhibit great super-hydrophobic and lipophobic properties together with exceptional time stability.

Synthesis and properties of polythiophenes with conjugated side‐chains containing carbon–carbon double and triple bonds

AbstractTwo soluble side‐chain conjugated polythiophenes, poly{3‐[2‐(4‐octyloxy‐phenyl)‐vinyl]‐thiophene} (P3OPVT) and poly{3‐(4‐octyloxy‐phenylethynyl)‐thiophene} (P3OPET) have been synthesized successfully. In P3OPVT and P3OPET, substituted benzene rings are connected with the polythiophene backbone through trans carbon–carbon double bond and carbon–carbon triple bond, respectively. Absorption spectra of the P3OPVT and P3OPET both show two absorption peaks located in UV and visible region, respectively. The results of optical and electrochemical measurements indicate that the conjugated side‐chains can reduce the bandgap effectively. This type of side‐chain conjugated polythiophenes may be promising for the applications in polymer photovoltaic cells and field effect transistors. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2206–2214, 2006

Synthesis and properties of novel fluorinated ester substituted polythiophenes

The electronic properties of the conjugated backbone of polythiophene can be tailored by the incorporation of perfluoroalkyl ester substituents. A polythiophene substituted with two different kinds of semifluoro and perfluoroalkyl esters were prepared by FeCl 3 oxidative polymerization. Both polymers were found to be highly soluble in common organic solvents, such as CHCl 3, THF and acetone. The influence of bulky fluoroalkyl substitutions on electrical conductivity, electronic absorption, fluorescence and surface properties of polymer films were investigated, and the properties were compared with poly(3-octylthiophene) synthesized under similar experimental conditions.

Synthesis of Highly Fluorescent Polythiophene with Polystyrene Branches Using ATRP

Abstract The graft copolymer containing a polythiophene (PT) backbone and polystyrene branches with superior solubility and processability was obtained by the atom transfer radical polymerization (ATRP) of styrene from the initiating sites on the PT backbone. The grafted PS branches could separate the PT chains and form a PS matrix for effectively trapping the PT in a solution conformation, which was advantageous to the improvement of fluorescent efficiency in the solid state.

A Family of Main-Chain Polymeric Lewis Acids: Synthesis and Fluorescent Sensing Properties of Boron-Modified Polythiophenes

A new family of main-chain organoborane polymeric Lewis acids (PTh-BAr) that contain Lewis acidic boron groups embedded into a polythiophene backbone has been prepared under mild conditions through tin-boron exchange reaction. When phenyl and pentafluorophenyl groups are attached to boron, blue and green luminescence is observed, respectively, while the attachment of ferrocenyl substituents leads to a characteristic red color. The incorporation of readily accessible highly Lewis acidic groups into the conjugated polymer backbone provides an opportunity for sensing of Lewis basic substrates. For instance, treatment of the polymer containing phenyl substituents on boron with pyridine leads to efficient quenching of the fluorescence, while the polymer containing ferrocenyl groups changes color from dark red to light orange.

Synthesis, characterization and structure dependence of thermochromism of polythiophene derivatives

In order to investigate the effect of the bulky pendant group and the spacer length between the pendant group and polythiophene main chain on the optical property of polythiophene backbone, a series of polythiophene derivatives were synthesized via copolymerization of 3-hexylthiophene with four different types of 4-((4-(phenyl)azo)phenoxy)alkyl-3thienylacetate. The alkyl spacers with different lengths, i.e., butyl, hexyl, octyl and undecyl groups were used between the bulky azobenzene group and the thiophene ring. The compositions and structures of these polythiophene derivatives were characterized. The structural dependence of thermochromic behaviour of these copolymers were systematically studied and results compared with poly(3-hexylthiophene) (P3HeT). A thermochromic temperature coefficient (CTC) was defined for the first time in an attempt to quantitatively compare the sensitivity of the thermochromism in the copolymers. The results have shown that these copolymers with a bulky azobenzene group in side chain have a higher (CTC) value than P3HT and the CTC value of the copolymers increase with increasing the spacer length.

Thin films of endohedral metallofullerenes embedded in polythiophene: a facile electrochemical preparation

A new electrochemical route for the synthesis of a hybrid thin film of endohedral metallofullerene (Dy@C 82 is used here) and polythiophene is presented, which exploits the unique, compatible redox properties of the couple. The electrochemical response of the resulting Dy@C 82/polythiophene film resembles that of Dy@C 82 in organic solvents except for the potential peak shifts, but is markedly different from that of a pure metallofullerene solid film. Both the polythiophene backbones and the Dy@C 82 moieties appear to retain their individual electrochemical properties in the hybrid film. The film was characterized by UV–visible and Fourier transform infrared absorption spectroscopy, time-of-flight secondary ion mass spectrometry, and scanning electron microscopy. The data suggest that the Dy@C 82 molecules have been uniformly dispersed in the polythiophene matrix, forming a compact film. The formation and the electrochemical response of the hybrid film have been systematically studied, refining the viable strategy for the encapsulation of metallofullerenes into conducting polymers.

Stable Polythiophene Semiconductors Incorporating Thieno[2,3-b]thiophene

This work describes a new design methodology that allows the preparation of air stable, semiconducting thiophene polymers with high charge carrier mobilities. The incorporation of thieno[2,3-b]thiophene into a polythiophene backbone introduces cross-conjugated double bonds that disfavor full delocalization, leading to high ionization potential in comparison to a fully conjugated polythiophene, with no reduction in charge carrier mobility. The resulting solution processable polymers exhibit charge carrier mobilities up to 0.15 cm2/V s and on/off ratios greater than 105 when measured in air. Transistors exhibit lifetimes of several months in air with no encapsulation necessary.

Photoluminescent behavior of poly(3-hexylthiophene) derivatives with a high azobenzene content in the side chains

A series of polythiophene derivatives with substantially higher azobenzene contents in the side chains were prepared via copolymerization of 3-hexylthiophene with four different types of 4-((4-(phenyl)azo)phenoxy)alkyl-3-thienylacetate. The alkyl spacers with different lengths, i.e. butyl, hexyl, octyl and undecyl groups were used between the azobenzene group and the thiophene ring. The compositions, structures and thermal properties of these polythiophene derivatives were characterized. The structural dependence of photoluminescent emission, photochromic behavior of these copolymers were systematically studied and compared with poly(3-hexylthiophene). The results show that the azobenzene substitution renders the polythiophene some interesting optical properties that can be modulated by UV light irradiation. In the azobenzene modified polythiophene, the intensity of photoluminescent emission associated with the conjugated polythiophene main chain was found to decrease significantly upon UV irradiation. The finding suggests that the photo-induced trans-cis isomerization of the azobenzene pendant groups has a significant effect on photoluminescent emission, particularly when short spacers are used between azobenzene groups and the main chain. However, the effect becomes less prominent when longer spacers are used between the azobenzene group and the main chain. Furthermore, UV irradiation of the copolymers also resulted in an increase in intensity and broadening of bandwidth for the absorption peak associated with the polythiophene backbones. Again the magnitude of intensity changes upon UV irradiation were found to be dependent on the spacer length between the azobenzene group and polythiophene main chain. Copyright © 2005 John Wiley & Sons, Ltd.

Tuning the Electronic Structure of Conjugated Polymers with Fluoroalkyl Substitution: Alternating Alkyl/Perfluoroalkyl-Substituted Polythiophene

The electronic properties of the conjugated backbone of polythiophene can be tailored by the incorporation of alkyl and perfluoroalkyl substituents. A regioregular copolymer with alternating alkyl and perfluoroalkyl substituents displays absorption and emission maxima between those of the homopolymers composed of the individual structural units. However, the combination of the alternating electron-rich and electron-poor units, together with a small twisting influence of the perfluoroalkyl groups, provides a material which displays enhanced solution-phase fluorescence and strong solid-state fluorescence which is absent for the wholly alkyl analogue.

Novel polythiophene regular copolymers from 3′,4′-diamino- and 3′,4′-dinitro-terthiophenes: Modulation of electronic properties via post-polymerization functionalization

Polythiophene regular copolymers bearing amino or nitro moieties directly linked to the conjugated backbone are produced by anodic coupling of 3′,4′-diamino- or 3′,4′-dinitro-terthiophenes. The polymers are characterized by cyclic voltammetry, FTIR reflection–absorption and UV–vis spectroscopy and in situ conductivity. Post-polymerization functionalization of polymer films leads to the quantitative transformation of the diamine to pyrazine and of the dinitro to diamine and subsequently pyrazine moieties. Conjugation of starting and ending functionalizations with the polythiophene backbone produces dramatic changes in electronic (electrochemical and optical) properties.

Metal‐containing conjugated oligo‐ and polythiophenes

AbstractConjugated polymers containing metal groups are an important class of new materials that may find application as sensors, non‐linear optical materials and in molecular electronics. Polythiophenes are an extensively studied class of conjugated polymers, that can be easily modified synthetically, and may be prepared using a variety of methods. Metal groups pendant to polythiophene backbones modulate the electronic, optical and redox properties of the conjugated backbone and can introduce novel structural motifs to these materials. Functionalization of oligo‐ and polythiophenes by Fe, Pd and Ru containing groups is discussed, along with the properties of some of these materials.

Calix[4]arene-functionalized poly-cyclopenta[2,1-b;3,4-b′]bithiophenes with good recognition ability and selectivity for small organic molecules for application in QCM-based sensors

Some C2v symmetric cyclopenta[2,1-b;3,4-b′]bithiophenes differently substituted at the 4 position with a calix[4]arene group were synthesized and electrochemically polymerized by anodic coupling. The polymers were characterized by cyclic voltammetry, UV-vis and FTIR spectroscopy. Quartz crystal microbalance analysis showed strong affinity and selectivity of the polymers for toluene and acetone from the gas phase. The absorption process associated with the calix unit was satisfactorily described through a Langmuir isotherm, while a very small linear contribution was given by the polythiophene backbone. The absorption capacity of these materials was found to be higher by a magnitude of three orders than those displayed by cyclopentabithiophene-based polymers devoid of the calix unit, thus supplying strong, though indirect, proof of the role played by the calix units in the absorption process.

Electrogenerated poly(thiophenes) derivatized by bipyridine ligands and metal complexes

The synthesis of a series of bithiophenic precursors of electrogenerated conjugated polymers functionalized by bipyridine ligands is described. The precursor structure involves two polymerizable groups attached at both ends of a bipyridine ligand and fixed at an internal β-position of thiophene via an alkylsulfanyl or alkoxy spacer. Electrochemical and optical data show that the low polymerization potential resulting from the association of 3,4-ethylenedioxythiophene (EDOT) and alkylsulfanyl or alkoxy thiophene combined with the multi-site polymerization approach allows a straightforward electrosynthesis of extensively conjugated and stable functionalized polymers. On the basis of these results, iron and ruthenium complexes of these precursors have been synthesized and electropolymerized. The analysis of the electrochemical behavior of the resulting polymers shows that they exhibit the typical electrochemical signature of both the conjugated polythiophene backbone and the immobilized metal complex.

Donor–acceptor polythiophene copolymers with tunable acceptor content for photoelectric conversion devices

The synthesis and characterization of a new series of substituted polythiophenes containing an electron acceptor anthraquinone moiety in the side chain are reported. The acceptor molar content was varied by the co-polymerization of both alkylthiophene and thiophene bearing anthraquinone monomers in different ratios. NMR analysis shows a good correlation between the monomer feed composition at the beginning of the polymerization and the actual unit composition of the backbone. The conjugation length and the chemical composition of the copolymers as a function of the molecular weight have been studied by size exclusion chromatography. Small angle X-ray scattering and UV-Vis absorption spectra have been used to monitor the degree of order and chain organization in the solid state. The materials exhibit a lamellar organization, in which the anthraquinone units of neighboring side chains are also organized to some degree in layered structures parallel to the polythiophene main chains. The photoluminescence measurements in solution suggest that, upon photoexcitation of the polythiophene backbone, the anthraquinone moieties act as electron acceptors and the conjugated backbone as electron donor. The tunability of the donor–acceptor ratio and the morphology in the solid state make these photoactive copolymers interesting candidates for organic photoelectric conversion devices.