Water-soluble Polythiophene Research Articles

Hydrogels from a Water-Soluble Zwitterionic Polythiophene: Dynamics under pH Change and Biomolecular Interactions Observed Using Quartz Crystal Microbalance with Dissipation Monitoring

The water-soluble zwitterionic polythiophene, poly(3-((S)-5-amino-5-carboxyl-3-oxapentyl)-2,5-thiophene) hydrochloride (POWT), is a conjugated polyelectrolyte (CPE) with properties well suited for biochip applications. CPEs readily form hydrogels when exposed to water-based buffer solutions or biomolecule solutions. In this work, we used in situ quartz crystal microbalance with dissipation (QCM-D) monitoring to collect information on the interaction between POWT films exposed to buffers with different pH and POWT/DNA chains. Our data show that POWT swells significantly when exposed to low-pH buffers, such as pH 4 acetate, this is seen as an increase in thickness and decrease in viscosity obtained via a Voight-based modeling of combined f and D QCM-D measurements. The magnitude of thickness and viscosity change upon changing from a pH 10 carbonate buffer to pH 4 acetate is 100% increase in thickness and 50% decrease in viscosity. The response of the hydrogel under pH change is well correlated with fluorescence data from POWT films on glass. The state of the hydrogel is important during interaction with biomolecules; illustrated by the observation that a swollen CPE hydrogel adsorbs a higher amount of DNA than a compacted one. In agreement with previous results, the QCM-D data confirmed that the POWT/DNA hydrogel sense complementary DNA specifically and with negligible binding of noncomplementary DNA. These results are important for efficient constructions of biochips in water environments using this class of materials.

Water-soluble polythiophene∕nanocrystalline TiO2 solar cells

We report the characteristics of polymer∕nanocrystalline solar cells fabricated using an environmentally friendly water-soluble polythiophene and TiO2 in a bilayer configuration. The cells were made by dropping the polymer onto a TiO2 nanocrystalline film and then repeatedly sweeping a clean glass rod across the polymer as it dried. The devices showed an open circuit voltage of 0.81 V, a short circuit current density of 0.35mA∕cm2, a fill factor of 0.4, and an energy conversion efficiency of 0.13%. The water-soluble polythiophene showed significant photovoltaic behavior and the potential for use in solar cells.

Self-Assembly of Supramolecular Chiral Insulated Molecular Wire

Supramolecular chiral insulated molecular wire was constructed by self-assembly of a neutral one-dimensional schizophyllan host and a water-soluble polythiophene guest. The work presented here will not only open a door to a new application of polysaccharides but also provide an important clue to prepare stable supramolecular insulated molecular wires with one-handed helical structure.

Water soluble polymer/carbon nanotube bulk heterojunction solar cells

We report the characteristics of polymer/quantum dot solar cells fabricated using a water-soluble polymer and carbon nanotubes in a bulk heterojunction configuration. The water-soluble polythiophene polymer showed significant photoresponse and the potential for use in photovoltaics. The addition of carbon nanotubes to the polymer resulted in an order of magnitude increase in the photoconductivity. Improved charge separation and collection was evidenced by the large difference between light and dark conductivities as well as the increase in both open circuit voltage and short circuit current. Finally, photovoltaic cells using aligned nanotubes showed further improvement in the photoconductivity and IV characteristics.

Non-ionic polythiophenes: a non-aggregating folded structure in water

The non-aggregating nature of a water-soluble pi-conjugated polythiophene has been characterised by concentration independent thermal denaturing.

Optical Emission of a Conjugated Polyelectrolyte: Calcium-Induced Conformational Changes in Calmodulin and Calmodulin−Calcineurin Interactions

Electronic polymers in aqueous media offer bioelectronic detection of biomolecular processes. Here we report fluorometric detection of calcium-induced conformational changes in calmodulin based on noncovalent assembly of calmodulin to a water-soluble zwitterionic polythiophene derivative. Assembly with calmodulin will induce a planar geometry and aggregation of the polymer chains, detected as a decrease of the intensity and a red shift of the fluorescence. Upon addition of Ca2+ the intensity of the emitted light is increased and blue-shifted. The geometrical alteration of the polymer chains can further be utilized for recording of the binding of calcineurin to the calcium-activated POWT−calmodulin complex. This novel methodology, using a conformation-sensitive probe, allows fluorometric detection of conformational changes in biomolecules and protein−protein interactions without any covalent modifications of the biomolecules. The rapid and selective method is based on noncovalent interactions between a zwitterionic polythiophene derivative and the biomolecule of interest. This offers a novel way to create microarrays without using covalent attachment of the receptor or labeling of the analyte.

Dynamics of complex formation between biological and luminescent conjugated polyelectrolytes—a surface plasmon resonance study

A water-soluble polythiophene, POWT, with zwitterionic peptide like side chains possess good characteristics for biosensor applications. The zwitterionic side chains of the polymer can couple to biomolecules via electrostatic and hydrogen bonding. This creates possibilities to imprint biomolecules to spin-coated polymer films with maintained functionality, and use the resulting matrix as a biosensor. Polymer-biomolecular interaction studies done with surface plasmon resonance (SPR) reveal a well performing sensor matrix with high affinity for DNA hybridizations as well as for protein detection. The responses are distinct and very specific. A directional dependence of antibodies binding to POWT layer has also been observed. The polymer films have also been characterized by optical methods. Emission and absorption measurements in different buffer systems confirm that the polymer matrix can undergo structural and conformational changes on surfaces. The dielectric function in the interval 300–800 nm of POWT is reported, based on variable angle spectroscopic ellipsometry. This modeling reveals that a considerable amount of water is included in the material. The polymer layer possesses the characteristics needed for biochip applications and micro array techniques.

Phosphonic Acid Derivatized Polythiophene: A Building Block for Metal Phosphonate and Polyelectrolyte Multilayers

A water-soluble polythiophene with pendant phosphonic acid groups, poly(3-(3‘-thienyloxy)propanephosphonate) (P3TOPP), has been synthesized. Matrix-assisted laser desorption ionization (MALDI) measurements showed that P3TOPP is an oligomer with an average chain length of 10 monomer units. In aqueous solutions it could be electrochemically oxidized and displayed self-acid doping at pH below 13. P3TOPP was used to prepare polyelectrolyte multilayers with poly(diallyldimethylammonium chloride) (PDADMA) and metal phosphonate multilayers with Zr4+ ions by the sequential layer-by-layer technique. The films were characterized by electrochemistry, atomic force microscopy (AFM), UV−vis, IR, and X-ray photoelectron (XPS) spectroscopy. A regular layer-by-layer growth was observed with both types of multilayers. The nature of the films was probed with XPS, which showed that the observed binding energies were characteristic for metal phosphonates and polyelectrolyte multilayers in Zr/P3TOPP and P3TOPP/PDADMA films, re...

Titration behaviors and spectral properties of hydrophobically modified water-soluble polythiophenes

The poly(3-thiopheneacetic acid) copolymers with 3- n-methylthiophene or with a 3- n-octadecylthiophene at the 3-position of a thiophene ring were synthesized. The solution and spectral properties of these hydrophobically modified polythiophenes have been studied by potentiometric titration, UV–visible spectroscopy. The effects of the rigid conjugated main chain, the steric hindrance and the hydrophobicity of a long alkyl side chain on the backbone conformational change have been discussed. We found that the conformational transition from the aggregate state to the extended state of the hydrophobically modified polythiophenes by the change of pH is sensitively restricted by the introduction of the hydrophobic alkyl or long alkyl side chains.

Solution and Electrical Properties of the Water-Soluble Poly(3-Thiopheneacetic Acid) and its Hydrogel

The water-swollen poly(3-thiopheneacetic acid) (P3TAA) gels with, various degree of cross-linkage (DCL) were synthesized. Doping behaviors of watersoluble polythiophene and its gel using I2 and concentrated HClO4 solution as dopants were studied. Electrical conductivity of doped polythiophene gel was investigated. In addition, we have investigated chemomechanical behavior by electric field, and the possibility of polythiophene gel as an electrode is introduced.

Doping behavior of water-soluble π-conjugated polythiophenes depending on pH and interaction of the polymer with DNA

Doping behavior of two kinds of water-soluble polythiophenes (PThs) (PTh with a CH 2CH 2CH 2SO 3M substituent at the 3-position, P3(RSO 3H)Th, and poly(ethylenedioxythiophene), PEDOTh) has been investigated spectroscopically at various pH under air. The p-doped (or oxidized) state of P3(RSO 3M)Th is stable at pH=1.0, whereas at pH levels higher than 4, the polymer is undoped. To the contrary, the p-doped state of PEDOTh is stable over a pH range of 1 to 7. Mixing of PEDOTh and a DNA (poly(G-C) 2) in a Tris buffer solution leads to a change of the UV-visible spectrum and precipitation of their adduct, supporting formation of an adduct between PEDOTh and poly(G-C) 2.

Titration Behavior and Spectral Transitions of Water-Soluble Polythiophene Carboxylic Acids. Volume 32, Number 12, June 15, 1999, pp 3964−3969.

Titration Behavior and Spectral Transitions of Water-Soluble Polythiophene Carboxylic Acids. Volume 32, Number 12, June 15, 1999, pp 3964−3969.

Titration Behavior and Spectral Transitions of Water-Soluble Polythiophene Carboxylic Acids

Water-soluble poly(3-thiophene acetic acid) (P3TAA) and its copolymers with 3-n-methylthiophene or with 3-n-octadecylthiophene were synthesized. The solution properties of these water-soluble polythiophene carboxylic acids were studied by potentiometric titration, viscosity measurements, and UV−visible spectroscopy. We have found that the Henderson−Hasselbach plot of the titration curve showed an inflection of the slope around pH = 5−6. The reduced viscosity and electronic spectra of the P3TAA aqueous solution also showed an abrupt change at this pH region. These results are quite different from that of a common flexible polyelectrolyte, such as poly(acrylic acid) (PAA) and strongly suggest that the pH-induced abrupt conformational changes occurred from the aggregated state to the extended state of the polymer main chain. The observed results are explained in terms of the rigid hydrophobic main chain and the nature of the conjugated polymer.

Highly Conducting Water-Soluble Polythiophene Derivatives

Water-soluble sodium poly(2-(3-thienyloxy)ethanesulfonate) and sodium poly(2-(4-methyl-3-thienyloxy)ethanesulfonate) have been synthesized. The sulfonic acid form of these new polymers has revealed a self-acid-doping reaction that leads to stable, highly conducting (0.5−5 S/cm) materials together with low absorption in the visible range. This process is reversible, and upon deprotonation, the insulating and dark polymers are recovered. The high doping and conductivity levels seem to be related to the relatively low oxidation potentials (0.44−0.50 V vs Ag/AgCl) of these polymers, which allows an almost complete (reversible) oxidation reaction in air (oxygen), catalyzed by the presence of the sulfonic acid moiety.

Self-Assembly and Disassembly of Regioregular, Water Soluble Polythiophenes: Chemoselective Ionchromatic Sensing in Water

The development of polythiophene (PT) derivatives with essentially 100% head-to-tail (HT) couplings1,2 has led to the discovery of materials that self-assemble both in solution and in the solid state. Light-scattering studies on regioregular, HTpoly(3-dodecylthiophene) (HT-PDDT) show that a supramolecular organization occurs via intermolecular aggregation.3 This solution aggregation is precursive to a microcrystalline, self-assembled structure which has been characterized by X-ray studies.1,2,4 Polythiophenes possessing this metastable organization evidence high electrical conductivities1,2,5-8 and very small bandgaps. Previous work in our lab has shown that both conformational order and solid state organization in regioregular PT derivatives are remarkably sensitive to the placement and nature of the substituent chains.1,6,7,9 This sensitivity provides the opportunity to design new conducting polymers in which self-assembly is controlled by environmental factors. One remarkable example is HT-2,5-poly(thiophene-3-propionic acid) (3, PTPA). This polymer was designed such that upon deprotonation, water soluble polythiophene salts are formed.10 Both 3 and its partially deprotonated derivative 5 undergo protein-like hydrophobic assembly, with subsequent H-bond stabilization, to generate a self-assembled conducting polymer aggregate. Varying the size of the counterion in the carboxylate polymer changes the effective steric bulk of the substituent. Small cations favor a self-assembled (purple) state and large cations can completely disrupt the aggregated phase. In fact, a remarkable chemoselective counterion size-dependent chromaticity (Figure 1) is observed for polymer 5. The UV-vis λmax can be varied over a 130 nm range (from purple to yellow) simply by changing the countercation. Initially, we prepared the carboxylate precursor polymer 2 using the Ni(dppp)Cl2 cross-coupling method for the synthesis of HT polythiophenes.5,6,9 This method leads to low molecular weights (Mn ) 1.5-3.0 K), low yields (<5%), and polymers that show variable ionic chromaticity. However, the regioregular oxazoline polythiophene (2) (Mn ) 8 K, PDI ) 1.2) is prepared (Scheme 1) from monomer11 1 in high yields (84%)

Dependence of swelling behaviour and electrochemical activity of water-soluble polythiophene films on the nature of the electrolyte

Abstract Electrochemical activity of a cast film of a water-soluble polythiophene, poly(3-(3′-thienyl)propanesulphonic acid) (PTS), is examined in various electrolyte solutions. The PTS film is electroactive in 0.1 M tetra(n-butyl)ammonium perchlorate (TBAClO4) + acetonitrile. In contrast, the film is inactive in 0.1 M LiClO4 + acetonitrile, even in the presence of TBA+, while addition of water (above 0.1 M) activates it. These characteristics are related to the film swelling; the PTS film is electroactive only when it is swollen. Water swells the film rapidly and TBA+ swells the film much more gradually. In the 0.1 M TBAClO4 + acetonitrile, potential cycling accelerates the film swelling owing to break-in behaviour. Well-swollen films do not exhibit break-in.