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Novel organic electrically conductive organic fibers (ECFs) have been fabricated using a facile, economical and scalable technique by staining nonconductive fibers (both natural and synthetic) with a conductive ink composed of two intrinsically conductive materials, i.e., single walled carbon nanotubes (SWCNTs) and regioregular poly(3-hexylthiophene) (rr-P3HT). These organic ECFs exhibit low resistance of 0.50 kΩ cm–1 with a conductive ink composed of 0.8 mg/mL of SWCNTs and 1.6 mg/mL of P3HT while maintaining the mechanical properties of the original fibers. These organic ECFs were characterized by resistance measurements, Raman spectroscopy, scanning electron microscopy, transmission electron microscopy and stress–strain measurements. Finally, the recording properties of the organic ECFs were examined by both electromyography and electrocardiography in terms of the signal-to-noise ratio, which was found to be similar and/or exceeded the data obtained by standard metal electrodes. [ABSTRACT FROM AUTHOR]

A conjugated polymer-based supramolecular system is designed for discrimination of virus and microbes. The supramolecular system is composed of cationic polythiophene derivative (PT) and barrel-shaped macrocyclic molecular cucurbit[7]uril (CB[7]). Because PT and PT/CB[7] complexes possess different interaction manners toward virus and microbes, the rapid and simple discrimination of virus and microbes was realized through polymer fluorescence intensity change assisting with standard linear discriminant analysis (LDA). The supramolecular strategy would expand the idea of designing biological probes and further promote the extensive application of conjugated polymer materials in biosensor field. [ABSTRACT FROM AUTHOR]

This research focuses on the design of biocompatible materials/scaffold suitable for use for tissue engineering. Porous fiber mats were produced through electrospinning of polythiophene phenylene (PThP) conducting polymers blended with poly(lactide-co-glycolic acid) (PLGA). A peptide containing an arginylglycylaspartic acid (RGD) fragment was synthesized using solid phase peptide synthesis and subsequently grafted onto a PThP polymer using azide-alkyne "click" chemistry. The obtained RGD functionalized PThP was also electrospun into a fiber mat. The electrospun mats' morphology, roughness and stiffness were studied by means of scanning electron microscopy (SEM) and atomic force microscopy (AFM) and their electroactivity by cyclic voltammetry. The fibers show excellent cytocompatibility in culture assays with human dermal fibroblasts-adult (HDFa) and human epidermal melanocytes-adult (HEMa) cells. The electrospun fibers' roughness and stiffness changed after exposing the fiber mats to the cell culture medium (measured in dry state), but these changes did not affect the cell proliferation. The cytocompatibility of our porous scaffolds was established for their applicability as cell culture scaffolds by means of investigating mitochondrial activity of HDFa and HEMa cells on the scaffolds. The results revealed that the RGD moieties containing PThP scaffolds hold a promise in biomedical applications, including skin tissue engineering. [ABSTRACT FROM AUTHOR]

Two new polymer systems, poly(3-phenylenevinylene)thiophene (P3PVT) and poly(3-phenyl)thiophene (P3PT), were designed with the aim of obtaining a helical conjugated polymer via a living polymerization. The polymerization proceeded without transfer and termination reactions via the Kumada catalyst transfer condensative polymerization (KCTCP) mechanism, confirming the living nature of the polymerization. Solvatochroism and circular dichroism (CD) experiments showed the helical nature of P3PVT and the stacking behavior of P3PT in poor solvent conditions. Block copolymers of 3-alkyl-substituted polythiophenes and helical P3PVT were prepared to determine the aggregation behavior of such systems. Solvatochroism, CD, and AFM measurements showed that the blocks influence each other's behavior. If the P3AT block stacks before the helical P3PVT block organizes, one-handed helix formation is hindered. If helix formation occurs first, the stacking behavior is not influenced. [ABSTRACT FROM AUTHOR]

Conjugated polymers possessing polar functionalities were shown to effectively anchor singlewalled carbon nanotubes (SWNTs) to the surface of highcapacity anode materials and enable the formation of electrical networks. Specifically, poly[3-(potassium-4-butanoate) thiophene] (PPBT) served as a bridge between SWNT networks and various anode materials, including monodispersed Fe3O4 spheres (sFe3O4) and silicon nanoparticles (Si NPs). The PPBT π-conjugated backbone and carboxylate (COO-) substituted alkyl side chains, respectively, attracted the SWNT π-electron surface and chemically interacted with active material surface hydroxyl (-OH) species to form a carboxylate bond. Beneficially, this architecture effectively captured cracked/pulverized particles that typically form as a result of repeated active material volume changes that occur during charging and discharging. Thus, changes in electrode thickness were suppressed substantially, stable SEI layers were formed, electrode resistance was reduced, and enhanced electrode kinetics was observed. Together, these factors led to excellent electrochemical performance. [ABSTRACT FROM AUTHOR]

The internal structure and cross-sectional geometry of fiber-like poly(3-hexylthiophene)-based block copolymer micelles has been determined using small- and wide-angle X-ray scattering (SAXS and WAXS, respectively) techniques alongside electron and atomic force microscopies. WAXS of concentrated micellar solutions demonstrated that the block copolymers form crystalline-core micelles in solvents selective for the corona-forming block. Furthermore, by generating macroscopic fibers from micellar solutions, it was possible to align the micelles and discern the type and orientation of the unit cell within the core. Using the unit cell information gained from the wide-angle measurements, in conjunction with the structural insights gained from the microscopy techniques, it was possible to form a complete picture of the cross-sectional geometry of the micelles, whereby the polymer chains lie perpendicular to the long axis of the micelle core and do not undergo chain folding. Finally, this information was used to propose a self-assembly mechanism and to construct and validate a model for the small-angle scattering data, revealing the inherent flexibility of the micelles. [ABSTRACT FROM AUTHOR]

In the present report, we focused on the study of the out-of-plane electrical transport of multiwalled carbon nanotube (MWCNT)-doped poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) composites (PEDOT:PSS-MWCNTs) as electrodes for solar cell applications. The out-of-plane direct current and alternating current electrical transport, rarely studied but not less relevant, was additionally supported with in-plane and out-of-plane confocal Raman microscopy and grazing incidence small-angle X-ray scattering characterizations. The main relevance of our study is the monitoring of the polymer structure all across the polymeric film by using confocal Raman spectroscopy and its correlation with electrical transport. Modifications in the PEDOT benzenoid and quinoid conformations were observed in the vicinities of MWCNTs, and the enrichment of PSS at the indium tin oxide electrode interface was also evidenced. In consequence, the low MWCNT loadings into PEDOT:PSS lead to an increase of the out-of-plane conductivity, but the heavier MWCNT loadings lead to a drastic decrease. The tuning of the doping level of these polymer composites and the understanding of the interface structure are crucial to fabricate electrodes with higher out-of-plane conductivities for organic solar cell applications. [ABSTRACT FROM AUTHOR]

Janus-type Au/polythiophene (PT) composites have been prepared by utilizing the liquid/liquid interface between water (W) and a hydrophobic ionic liquid (IL) as the redox reaction site. AuCl4– is reductively deposited, and terthiophene is oxidatively polymerized spacio-selectively at the IL|W interface, leading to the formation of the Au/PT composites. The composites are Janus-type Au-attached PT plates with two surface morphologies, flat surface and flowerlike surface at the W and IL sides of the plates at the IL|W interface, respectively. Not only surface morphologies but also attached Au structures are different at the two surfaces; Au microurchins on the flat surface and dendritic Au nanofibers on the flowerlike surface. Optical and scanning electron microscopic observations have revealed that nanofibers and microurchins are formed at the early and later stage of the reaction, respectively. Electrochemistry at the IL|W interface has illustrated that electron transfer across the IL|W interface during the formation of the Janus-type Au/PT composites is coupled with ion transfer of AuCl4– to compensate for the charge unbalance in the two liquid phases. AuCl4– transferred into IL is found to be the source of the dendritic Au nanofibers formed at the IL side of the PT plates. [ABSTRACT FROM AUTHOR]

Doping of thin films of semiconducting polymers provides control of their electrical conductivity and thermopower. The electrical conductivity of semiconducting polymers rises nonlinearly with the carrier concentration, and there is a lack of understanding of the detailed factors that lead to this behavior. We report a study of the morphological effects of doping on the electrical conductivity of poly(3-hexylthiophene) (P3HT) thin films doped with small molecule 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ). Resonant soft X-ray scattering shows that the morphology of films of P3HT is not strongly changed by infiltration of F4TCNQ from the vapor phase. We show that the local ordering of P3HT, the texture and form factor of crystallites, and the long-range connectivity of crystalline domains contribute to the electrical conductivity in thin films. The thermopower of films of P3HT doped with F4TCNQ from the vapor phase is not strongly enhanced relative to films doped from solution, but the electrical conductivity is significantly higher, improving the thermoelectric power factor. [ABSTRACT FROM AUTHOR]

In this work we report a broad scenario for the patterning of semiconducting polymers by laser-induced periodic surface structures (LIPSS). Based on the LIPSS formation in the semicrystalline poly(3-hexylthiophene) (P3HT), we have extended the LIPSS fabrication to an essentially amorphous semiconducting polymer like poly[N-90-heptadecanyl-2,7-carbazole-alt-5,5-(40,70-di-2-thienyl-20,10,30-benzothiadiazole)] (PCDTBT). This polymer shows a good quality and well-ordered nanostructures not only at the 532 nm laser wavelength, as in the case of P3HT, but also at 266 nm providing gratings with smaller pitch. In addition, we have proven the feasibility of fabricating LIPSS in the P3HT/PCDTBT (1:1) blend, which can be considered as a model bulk-heterojunction for all-polymer solar cells. In spite of the heterogeneous roughness, due to phase separation in the blend, both P3HT and PCDTBT domains present well-defined LIPSS as well as a synergy for both components in the blend when irradiating at wavelengths of 532 and 266 nm. Both, P3HT and PCDTBT in the blend require lower fluence and less pulses in order to optimize LIPSS morphology than in the case of irradiating the homopolymers separately. Near edge X-ray absorption fine structure and Raman spectroscopy reveal a good chemical stability of both components in the blend thin films during LIPSS formation. In addition, scanning transmission X-ray spectro-microscopy shows that the mechanisms of LIPSS formation do not induce a further phase segregation neither a mixture of the components. Conducting atomic force microscopy reveals a heterogeneous electrical conductivity for the irradiated homopolymer and for the blend thin films, showing higher electrical conduction in the trenches than in the ridge regions of the LIPSS. [ABSTRACT FROM AUTHOR]

A significant tuning of optoelectronic properties of polythiophene (PT) chains due to Hofmeister iodide (I-) ion is demonstrated in ampholytic polythiophene [polythiophene-g-poly{(N,N,N-trimethylamino iodide)ethyl methacrylate-co-methacrylic acid}, APT] at different pHs. In acidic medium, the absorption and emission signals of PT chromophore exhibit appreciable blue shift in the presence of I- as counteranion only. The cooperative effect of undissociated -COOH and quaternary ammonium groups immobilize I- near the apolar PT chain causing threading of grafted chains and hence twisting of the backbone attributing to the blue shift. As medium pH is increased, dethreading of the PT backbone occurs due to ionization of -COOH group, releasing quencher iodide ions from the vicinity of the PT chains resulting in a red shift in absorption and a sharp hike in fluorescence intensity (390 times) for an increase of excitons lifetime. With an increase of pH, morphology changes from a multivesicular aggregate with vacuoles to smaller size vesicles and finally to nanofibrillar network structure. Dethreading is also found when APT interacts with RNA showing a significant hike of fluorescence (22 times) for displacing iodide ions forming a nanofibrillar network morphology. Threading and dethreading also affect the resistance, capacitance, and Warburg impedance values of APT. Molecular dynamics simulation of a model APT chain in a water box supports the threading at lower pH where the iodide ions pose nearer to the PT chain than that at higher pH causing dethreading. So the influence of Hofmeister I- ion is established for tuning the optoelectronic properties of a novel PT based polyampholyte by changing pH or by conjugating with RNA. [ABSTRACT FROM AUTHOR]

Molecular p-doping of the conjugated polymer poly(3-hexylthiophene) (P3HT) with 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ) is a widely studied model system. Underlying structure-property relationships are poorly understood because processing and doping are often carried out simultaneously. Here, we exploit doping from the vapor phase, which allows us to disentangle the influence of processing and doping. Through this approach, we are able to establish how the electrical conductivity varies with regard to a series of predefined structural parameters. We demonstrate that improving the degree of solid-state order, which we control through the choice of processing solvent and regioregularity, strongly increases the electrical conductivity. As a result, we achieve a value of up to 12.7 S cm-1 for P3HT:F4TCNQ. We determine the F4TCNQ anion concentration and find that the number of (bound + mobile) charge carriers of about 10-4 mol cm-3 is not influenced by the degree of solid-state order. Thus, the observed increase in electrical conductivity by almost 2 orders of magnitude can be attributed to an increase in charge-carrier mobility to more than 10-1 cm2 V-1 s-1. Surprisingly, in contrast to charge transport in undoped P3HT, we find that the molecular weight of the polymer does not strongly influence the electrical conductivity, which highlights the need for studies that elucidate structure-property relationships of strongly doped conjugated polymers. [ABSTRACT FROM AUTHOR]

We report a directly photopatternable polythiophene derivative PToNB with o-nitrobenzyl (oNB)-functionalized side chains. PToNB has unique phototunable solubilities programmed through three stages: (i) organic-soluble/aqueous-insoluble, (ii) organic-insoluble/aqueous-insoluble, and (iii) organic-insoluble/aqueous soluble. The capability to control conjugated polymer solubility with spatiotemporal precision and orthogonal developer solvents through three stages allows for direct patterning of this conjugated polymer and provides flexibility to choose between positive and negative tone photolithography. This approach to photomodulate solubility also enables all-solution processing of multilayer stacked conjugated polymer films; we demonstrate here direct two-layer photopatterning with this novel conjugated polymer photoresist. [ABSTRACT FROM AUTHOR]

Antibiotic-resistant bacterial infections have become a serious public health threat. In an effort to address this threat, we develop an imidazolium-functionalized conjugated polyelectrolyte that exhibits profound light-activated biocidal activity. Here we report the synthesis, photophysical properties, and biocidal activity of a regioregular head-to-tail polythiophene substituted with cationic imidazolium units (P3HT-Im) prepared by Grignard metathesis controlled polymerization. In water, P3HT-Im has a broad absorption in the visible region and exhibited a remarkably high biocidal efficiency with both Gram-positive and Gram-negative bacteria at sub-microgram per milliliter concentrations. Moreover, mammalian cell studies suggest that P3HT-Im is nontoxic to mammalian cells at concentrations of ≤20 μg/mL over a short time scale (≤1 h) in the dark and light, and the targeting rate-dependent selective mechanism is revealed. This study demonstrates the capability of P3HT-Im to achieve selective imaging and inactivation of bacteria over mammalian cells, suggesting that the polymer has significant potential for ameliorating antibiotic-resistant bacteria in a clinical setting. [ABSTRACT FROM AUTHOR]

We used molecular dynamics simulations and the Green-Kubo modal analysis (GKMA) method as well as sonification to study the modal contributions to thermal conductivity in individual polythiophene chains. The simulations suggest that it is possible to achieve divergent thermal conductivity in individual polythiophene chains of certain lengths, with periodic boundary conditions. Application of the GKMA method further allowed for exact pinpointing of the modes responsible for the anomalous behavior. The analysis showed that transverse vibrations in the plane of the aromatic rings at low frequencies -0.05 THz are primarily responsible for the divergence. Within the integration time, one mode in particular exhibits a thermal conductivity contribution greater than 100 W m-1 K-1. Further investigation showed that the divergence arises from persistent correlation between the three lowest frequency modes on chains that have exact multiples of 30 unit cells in length. Sonification of the mode heat fluxes revealed regions where the heat flux amplitude yields a somewhat sinusoidal envelope with a long period similar to the relaxation time. This characteristic in the divergent mode heat fluxes gives rise to the overall thermal conductivity divergence, which strongly supports earlier hypotheses that attribute the divergence to correlated phonon-phonon scattering/interactions as opposed to a lack of scattering/interaction among modes (e.g., infinite relaxation time/ballistic transport). [ABSTRACT FROM AUTHOR]

We report on the controlled synthesis of naphthalenediimide-bithiophene copolymers with varying ratios of 2,6- and 2,7-linkage (parent polymer: poly{[N,N'-bis(2-octyldodecyl)-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5'-(2,2'-bithiophene)} P(NDI2OD-T2)). Monomers with different ratios of 2,6- and 2,7-regioisomers could be isolated, leading to n-type polymers with tunable regioregularity. With increasing content of 2,7-linkage in the polymer backbone the aggregation tendency can be drastically reduced. Both the reduction behavior and the electron transport properties are very similar for all systems. For the regioregular system we find mobility values of 3 × 10-1 cm²/(V s); the regioirregular systems become comparable with values as high as 7 × 10-2 cm²/(V s) when temperature annealing is employed. This means that regioregularity seems to have an overall lower effect in comparison to classical systems such as poly(3-hexylthiophene). Tuning regioregularity in such systems therefore provides a powerful tool to optimize processing without deteriorating device performance. We even find that device performance of bulk-heterojunction solar cells with a polythiophene derivative as donor strongly improves upon use of the regioirregular systems. [ABSTRACT FROM AUTHOR]

Surfactants are considered to have a strong affinity to metal ions. Thus, it is a novel design by employing sodium dodecylbenzenesulfonate (NaDBS) and hexadecyltrimethylammonium bromide (CTAB) surfactants to functionalize polythiophene/TiO2 composite via a facile and green method to improve the Pb2+ removal efficiency from the aqueous solution. Techniques such as Fourier transform infrared spectroscopy, zeta potential analysis, thermogravimetric analysis, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and N2 isotherm analysis revealed changes in surface properties after modification, and adsorption active sites were also extensively detected. Batch adsorption investigations were carried out to study their adsorption behaviors for lead(II), and the diffusion process was carefully investigated and described via kinetic models including the Weber-Morris and pseudo-second-order model. The results indicated that modification with NaDBS or CTAB significantly changed the adsorption behavior and increased the monolayer adsorption capacity of polythiophene/TiO2 composite for Pb2+, from 151.52 mg/g to 198.41 or 213.22 mg/g. The entire adsorption process results comprehensively confirmed that the diffusion rate of Pb2+ ions was controlled by the film and intraparticle diffusion, and the combination rate of Pb2+ with active sites was limited by chemisorption. Pb2+ ions were also detected to interact with adsorption active sites including sulfur atoms, hydroxyl groups, and surfactants. [ABSTRACT FROM AUTHOR]

The stiff backbones of conjugated polymers can lead to a rich phase behavior that includes both crystalline and liquid crystalline phases, making measurements of the glass transition challenging. In this work, the glass transitions of regioregular poly(3-hexylthiophene-2,5-diyl) (RR P3HT), regiorandom (RRa) P3HT, and poly((9,9-bis(2-octyl)-fluorene-2,7-diyl)-alt-(4,7-di(thiophene-2-yl)-2,1,3-benzothiadiazole)-5',5"-diyl) (PFTBT) are probed by linear viscoelastic measurements as a function of molecular weight. We find two glass transition temperatures (Tg's) for both RR and RRa P3HT and one for PFTBT. The higher Tg, Tα, is associated with the backbone segmental motion and depends on the molecular weight, such that the Flory-Fox model yields Tα = 22 and 6 °C in the long chain limit for RR and RRa P3HT, respectively. For RR P3HT, a different molecular weight dependence of Tα is seen below Mn = 14 kg/mol, suggesting this is the typical molecular weight of intercrystal tie chains. The lower Tg (TαPE ≈ -100 °C) is associated with the side chains and is independent of molecular weight. RRa P3HT exhibits a lower Tα and higher TαPE than RR P3HT, possibly due to a different degree of nanophase separation between the side chains and the backbones. In contrast, PFTBT only exhibits one Tg above -120 °C, at 144 °C in the long chain limit. [ABSTRACT FROM AUTHOR]

A new family of thieno[3,4-b]thiophene-benzodithiophene terpolymers (PBTClx) have been designed and synthesized, in which the chlorine/fluorine content has been adjusted and optimized. As the content of chlorine is increased in polymers, the twist angle between the donor and acceptor is increased, which leads to a diminishment in the planarity and conjugation. As a result, the UV-vis absorption is continuous blue-shifted, and the band gap increases from 1.57 to 2.04 eV when the chlorinated moieties increased from 0 to 100%. The highest occupied molecular orbital (HOMO) levels of those polymers are decreased by increasing the content of chlorinated moiety, which opens a window to constantly modify the Voc values and eventually meets a balance point for optimized solar energy conversion. The highest power conversion efficiency of 8.31% is obtained by using PBTCl25 as the donor and PC71BM as the acceptor in polymer solar cells (PSCs), in which the Voc increased from 0.79 to 0.82 V after 25% chlorinated monomer involved in copolymerization. Herein, the chlorine replacement could be a good method to further pump the solar conversion by increasing the open circuit voltage without reducing other factors of the polymer solar cells. [ABSTRACT FROM AUTHOR]

Cellulose nanocrystals (CNCs) are bioderived, rodlike particles that form a chiral nematic liquid crystal (LC) in water. In this work, CNCs were used to induce long-range order in a semiconducting polymer, poly[3-(potassium-4-butanoate) thiophene-2,5-diyl] (PPBT). When mixed with CNCs, it was found that PPBT was incorporated into the liquid crystal “template” to form ordered structures with highly birefringent domains, as observed under polarized light. We show that the π–π interactions between polymer chains, which contribute considerably to the energetics of the semiconducting system, are directly influenced by the presence and packing of the liquid crystal phase. Upon increasing the concentration of CNCs from the isotropic to chiral nematic regime, we observe a bathochromic shift in the UV–vis spectra and the emergence of the 0–0 vibrational peak, suggesting enhanced π–π stacking leading to chain coplanarization. Furthermore, the chiral nature of the PPBT/CNC mixture was evidenced by a negative peak in circular dichroism (CD) spectroscopy, promoting the notion that the polymer chains followed the helicoidal twist of the chiral nematic liquid crystal host. At high temperatures, the peak height ratios and overall intensities of the UV–vis and CD spectra associated with PPBT decreased as the chiral nematic pitch grew larger in size. [ABSTRACT FROM AUTHOR]

Nanocomposites of polypyrrole (PPY) and polythiophene (PTP) were prepared with [Fe(TEMED)(H2O)(CN)3]·H2O photoadduct via the oxidative chemical polymerization method. The morphologies and structures of the photoadduct and nanocomposites were studied by XRD, SEM, and FTIR characterization techniques. Thermal and electrical properties of nanocomposites were found to be significantly improved in comparison to pristine polymers. The photocatalytic activities of samples were studied by monitoring the degradation of methyl orange (MO), methylene blue (MB), Rhodamine B (RhB), and Eosin Gelblich (EG) dyes under irradiation, using a UV-vis spectrophotometer. The samples were found to exhibit promising photocatalytic activities against dye degradation under light illumination. Results also showed attenuation in photodegradation of the MO dye by the disodium ethylenediaminetetraacetate dihydrate (EDTA-Na2; C10H14N2Na2O8·2H2O) (hole scavenger) and tert-butyl alcohol (C4H10O) (radical scavenger). This clearly indicated the generation of reactive oxygen species (ROS) in the photocatalytic activity. The synthesized nanocomposite systems were also explored for the treatment of dye industry effluents in wastewater. [ABSTRACT FROM AUTHOR]

To understand the rate determining processes during the equilibration of poly(3,4-ethylenedioxythiophene):polystyrenesulfonate-based (PEDOT(PSS)-based) solid contact (SC) ion-selective electrodes (ISEs), the surfaces of Pt, Au, and GC electrodes were coated with 0.1, 1.0, 2.0, and 4.0 µm thick galvanostatically deposited PEDOT(PSS) films. Next, potential vs time transients were recorded with these electrodes, with and without an additional potassium ion-selective membrane (ISM) coating, following their first contact with 0.1 M KCl solutions. The transients were significantly different when the multilayered sensor structures were assembled on Au or GC compared to Pt. The differences in the rate of equilibration were interpreted as a consequence of differences in the hydrophilicity of PEDOT(PSS) in contact with the substrate electrode surfaces based on X-ray photoelectron spectroscopy (XPS) and synchrotron radiation-XPS (SR-XPS) analysis of 10-100 nm thick PEDOT(PSS) films. The influence of the layer thickness of the electrochemically deposited PEDOT(PSS)-films on the hydrophilicity of these films has been documented by contact angle measurements over PEDOT(PSS)-coated Au, GC, and Pt electrode surfaces. This study demonstrates that it is possible to minimize the equilibration (conditioning) time of SC ISEs with aqueous solutions before usage by optimizing the thickness of the SC layer with a controlled ISM thickness. PEDOT(PSS)-coated Au and GC electrodes exhibit a significant negative potential drift during their equilibration in an aqueous solution. By coating the PEDOT(PSS) surface with an ISM, the negative potential drift is compensated by a positive potential drift related to the hydration of the ISM and activity changes at the PEDOT(PSS)|ISM interface. The potential drifts related to activity changes in the ISM have been determined by a novel adaptation of the "sandwich membrane" method. [ABSTRACT FROM AUTHOR]

By using different polysaccharide and polysulfonylimide type polyelectrolytes for the synthesis of aqueous PEDOT:polyelectrolyte dispersions, the influence of the polyelectrolyte backbone and of the anionic groups on the properties of the resulting PEDOT:polyelectrolyte complex has been studied. The obtained PEDOT:polyelectrolyte systems were characterized regarding the doping and the morphology of the complexes in dispersion as well as regarding the optoelectronic properties and the morphology of the dry PEDOT:polyelectrolyte films. Polyelectrolytes with high molar mass, a rigid backbone, and strongly acidic functionalities resulted in highly conducting PEDOT:polyelectrolyte films, while polyelectrolytes with flexible backbones and weakly acidic groups resulted in insulating PEDOT:polyelectrolyte systems. These findings could help to develop a palette of new PEDOT:polyelectrolyte systems, which correspond better to the specific requirements of different applications. [ABSTRACT FROM AUTHOR]

Multiscale assembly of poly(3-alkylthiophene)s complexed with various alkyl-chain surfactant architectures has been investigated in dilute and concentrated solutions by means of ultraviolet-visible absorption and fluorescence spectroscopy, polarized optical microscopy, small-angle X-ray scattering, and four-point probe conductivity measurements. Supramolecular complexation occurs via ionic interactions between poly(3-alkylthiophene)s electrolytes and ionic surfactants. In dilute solutions, the supramolecular complex undergoes a coil-to-rod conformational transition as evidenced by a time-dependent chromism. Spectroscopic studies on transition kinetics reveal an inverse first-order rate law. While surfactant architectures significantly affect the persistence length of the complexes, the inverse first-order rate law is maintained. When concentrated above a critical value, the supramolecular complex exhibits an isotropic-to-liquid crystalline transition yielding hexagonally ordered microstructures. The liquid crystalline phase boundaries are largely dependent on polymer and surfactant architectures. The correlations between the intrinsic rigidity of conjugated polymers, optoelectronic properties, and liquid crystalline formation are presented. The dried films made from the sheared liquid crystalline solutions inherit liquid crystalline monodomains and display four times faster charge transport along the backbone alignment direction than the perpendicular direction. [ABSTRACT FROM AUTHOR]

We have investigated the initial nucleation process of polythiophene derivatives by molecular dynamics simulations to elucidate the role of flexible side chains in the crystallization process. We considered poly(3-hexylthiophene) (P3HT), poly(3,3‴-dihexylquarterthiophene) (PQT6), poly(3-dodecylthiophene) (P3DDT), and poly(3,3‴-didodecylquaterthiophene) (PQT12), in which the lengths and densities of the alkyl side chains are different. In the case of the short side-chain molecules (P3HT and PQT6), the initial nucleation process is based on the following steps. At the beginning, the thiophene rings align and ordering of the main chains commences shortly afterward. Ordering of the flexible side chains is induced after formation of a stacked structure of rigid main chains. In the case of a long and dense side-chain molecule (P3DDT), the initial nucleation process shows different features. The ordering process of the thiophene rings or main chains becomes very slow, while that of side chains becomes fast. In addition, the local order of the main chains becomes lower than those of P3HT and PQT6. These simulation results reveal that long and dense side chains suppress the nucleation process, whereas long but low-density side chains lead to formation of stacked nuclei in a different manner from those observed for short side-chain molecules. [ABSTRACT FROM AUTHOR]

Polythiophenes (PTs) are promising electron donors in organic solar cells (OSCs) due to their simple structures and excellent synthetic scalability. Benefiting from the rational molecular design, the power conversion efficiency (PCE) of PT solar cells has been greatly improved. Herein, five batches of the champion PT (P5TCN-F25) with molecular weights ranging from 30 to 87 kg mol -1 were prepared, and the effect of the molecular weight on the blend film morphology and photovoltaic performance of PT solar cells was systematically investigated. The results showed that the PCEs of the devices improved first and then maintained a high value with the increase of molecular weight, and the highest PCE of 16.7% in binary PT solar cells was obtained. Further characterizations revealed that the promotion in photovoltaic performance mainly comes from finer phase separation structures and more compact molecular packing in the blend film. The best device stabilities were also achieved by polymers with high molecular weights. Overall, this study highlights the importance of optimizing the molecular weight for PTs and offers directions to further improve the PCE of PT solar cells.

We systematically varied the degree of fluorination along the backbone of a series of highly regioregular 3-hexylthiophene-based polymers, P3HT-50F, P3HT-33F, and P3HT-25F, in which 50%, 33%, and 25% of the thiophene units within the polymer chain contain fluorine atoms in the available 4-position, respectively. These materials were homopolymerized using the Kumada catalyst transfer polycondensation method from a set of mono-fluorinated bi-, ter-, and quarterthiophenes to ensure high polymer regioregularity and evenly spaced fluorine atoms along the conjugated thiophene backbone. The monomers were obtained from a synthetic route consisting of iterative Migita-Stille couplings of fluorinated and non-fluorinated 3-hexylthiophenes. The effect of the fluorine atoms on both polymer structure and properties is presented, with supporting quantum mechanical calculations that rationalize the intrinsic conformation preferences of the three P3HT derivatives. P3HT-50F (M̅ n = 34 kg/mol, 98.5% rr), P3HT-33F (M̅ n = 46 kg/mol, 98% rr), and P3HT-25F (M̅ n = 53 kg/mol, 95% rr) displayed HOMO levels of -5.34, -5.26, and -5.24 eV, bandgaps of 1.98, 1.98, and 1.97 eV, and average field-effect transistor hole mobilities of 4.5 × 10-3, 2.7 × 10-2, and 1.2 × 10-2 cm² V-1 s-1, respectively. [ABSTRACT FROM AUTHOR]

The photophysical properties of films of alkyl-substituted polythiophenes are governed by a subtle interplay between intra- and interchain electronic couplings. The intramolecular properties, however, are still not entirely clear because polythiophenes possess a strong tendency to form π-stacked aggregate structures with appreciable interchain couplings. Here we employ low-temperature single-molecule photoluminescence spectroscopy on isolated regioregular poly(3-hexylthiophene), P3HT, chains with different, but well-defined molecular weights to reveal the intrachain properties of their emitting sites. We find that the inhomogeneous distribution function of the zero-phonon lines (ZPL) is very narrow (<480 cm-1, 60 meV), which indicates a low degree of torsional disorder of the P3HT backbone on length scales of the emitting sites (despite a large mean dihedral angle). Moreover, the single-chain ZPLs are exclusively located in the high energy tail of the corresponding spectrum of a disordered ensemble. Using concentration-dependent measurements in combination with time-dependent density functional theory, we show that this spectral shift stems from aggregation-induced partial planarization and concomitant electronic coupling between segments of neighboring P3HT chains. [ABSTRACT FROM AUTHOR]

An advanced method is proposed to prepare helical graphite films with large domains of left- and right-handed spiral morphologies which are composed of fibril bundles using oxidized PEDOT films as carbonization substrates. Helical PEDOT (H-PEDOT) films, as carbonization precursors, are prepared via an electrochemical polymerization in an asymmetric reaction solution containing the chiral nematic liquid crystal (N*-LC), the monomer bis-EDOT, and an electrolyte. The N*-LCs are provided by mixing a spot of di- or tetra-substituted, axially chiral, binaphthyl compounds as the chiral dopants with the N-LC. In addition, a new type of chiral dopant bearing a cyanobiphenyl moiety, which is the same mesogenic core as that of the parent LC [4-cyano-4′-pentylbiphenyl], is used for preparing high miscible N*-LC systems. The distances between the fibril bundles of H-PEDOTs specifically depend on the helical twisting powers of the chiral dopants. In circular dichroism spectra, the H-PEDOTs in both neutral and oxidized states exhibit clear Cotton effects. In the preparation of the helical graphite films, substrates such as quartz and carbon plates cannot retain the spiral morphologies because of the substantial difference in the thermal shrinkage between the substrate and precursor. The oxidized PEDOT film used as a promising carbonization substrate has almost the same thermal shrinkage as the H-PEDOT film, which allows for a reduction in the deformation due to thermal shrinkage during the heat treatment. As a result, helical carbon and graphite films which have distinguished spiral morphologies are obtained via heat treatment at 800 and 2600 °C, respectively. [ABSTRACT FROM AUTHOR]

We report the synthesis of all-conjugated branched poly(thiophenes) with a control over the degree of nonlinearity via two different routes. In the first approach a branched monomer is polymerized using three different catalysts which differentiate in the degree of association to the π-system of the polymer backbone. In the second approach a copolymerization is performed with the branched and a linear monomer. In a next step the influence of the different degrees of nonlinearity on the optoelectronic properties is investigated by UV-vis and fluorescence spectroscopy. Finally, the thermal behavior, the morphology, and the electrical properties at the nanoscale of the material in solid state are studied using DSC and AFM techniques. [ABSTRACT FROM AUTHOR]

Control of higher-order polymer structures attracts a great deal of interest for many researchers when they lead to the development of materials having various advanced functions. Among them, conjugated polymers that are useful as starting materials in the design of molecular wires are particularly attractive. However, an equilibrium existing between isolated chains and bundled aggregates is inevitable and has made their physical properties very complicated. As an attempt to simplify this situation, we previously reported that a polymer chain of a water-soluble polythiophene could be isolated through complexation with a helix-forming polysaccharide. More recently, a covalently self-threading polythiophene was reported, the main chain of which was physically protected from self-folding and chain-chain π-stacking. In this report, we wish to report a new strategy to isolate a water-soluble polythiophene and to control its higher-order structure by a supramolecular approach: that is, among a few bile acids, lithocholate can form stoichiometric complexes with cationic polythiophene to isolate the polymer chain, and the higher-order structure is changeable by the molar ratio. The optical and morphological studies have been thoroughly performed, and the resultant complex has been applied to the selective recognition of two AMP structural isomers. [ABSTRACT FROM AUTHOR]

We report the effects of compressed CO2 molecules as a novel plasticization agent for poly(3-hexylthiophene) (P3HT)-conjugated polymer thin films. In situ neutron reflectivity experiments demonstrated the excess sorption of CO2 molecules in the P3HT thin films (about 40 nm in thickness) at low pressure (P = 8.2 MPa) under the isothermal condition of T = 36 °C, which is far below the polymer bulk melting point. The results proved that these CO2 molecules accelerated the crystallization process of the polymer on the basis of ex situ grazing incidence X-ray diffraction measurements after drying the films via rapid depressurization to atmospheric pressure: both the out-of-plane lamellar ordering of the backbone chains and the intraplane π-π stacking of the side chains were significantly improved, when compared with those in the control P3HT films subjected to conventional thermal annealing (at T = 170 °C). Electrical measurements elucidated that the CO2-annealed P3HT thin films exhibited enhanced charge carrier mobility along with decreased background charge carrier concentration and trap density compared with those in the thermally annealed counterpart. This is attributed to the CO2-induced increase in polymer chain mobility that can drive the detrapping of molecular oxygen and healing of conformational defects in the polymer thin film. Given the universality of the excess sorption of CO2 regardless of the type of polymers, the present findings suggest that CO2 annealing near the critical point can be useful as a robust processing strategy for improving the structural and electrical characteristics of other semiconducting conjugated polymers and related systems such as polymer:fullerene bulk heterojunction films. [ABSTRACT FROM AUTHOR]

Charge carrier mobilities in conjugated semicrystalline polymers depend on morphological parameters such as crystallinity, crystal orientation, and connectivity between ordered regions. Despite recent progress in the development of conducting polymers, the complex interplay between the aforementioned parameters and their impact on charge transport is not fully understood. By varying the casting solvents and thermal annealing, we have systematically modulated the crystallization of poly(3-hexylthiophene-2,5-diyl) (P3HT) and poly[2,5-bis(3-hexadecylthiophen-2-yl)thieno(3,2-b)thiophene] (PBTTT) thin films to examine the role of microstructure on charge mobilities. In particular, we achieve equal crystallinities through different processing routes to examine the role of structural parameters beyond the crystallinity on charge mobilities. As expected, a universal relationship does not exist between the crystallinity in either P3HT and PBTTT active layers and the charge mobility in devices. In P3HT films, higher boiling point solvents yield longer conjugation lengths, an indicator of stronger intracrystalline order, and therefore higher device mobilities. In contrast, the charge mobilities of PBTTT devices depend on the interconnectivity between crystallites and intercrystalline order in the active layer. [ABSTRACT FROM AUTHOR]

We have investigated how the addition of 1,8-diiodooctane (DIO) alters the formation of disordered and ordered phases in a film of poly(3-hexyl-thiophene-2,5-diyl) (P3HT). By combining in situ time-resolved absorption spectroscopy with 60 ms time resolution, optical and transmission electron microscopy and spatially resolved photoluminescence spectroscopy, we show that, in addition to the excitonic coupling, the film formation process during spin-coating as well as the subsequent long-time film drying process differ significantly when DIO is added to a solution of P3HT. During spin-coating, the addition of DIO reduces the actual time for transformation from disordered to ordered phase, even though it increases the time until the disorder-order transition sets in. In place of a solidification front, we observe an all-over solidification throughout the entire film. The phase separation between nonaggregated and aggregated phase increases when using DIO, with compositional variation in the content of aggregated phase on a micrometer scale. [ABSTRACT FROM AUTHOR]

Polythiophene-graft-polyampholyte (PTP) is synthesized using N,N-dimethylaminoethyl methacrylate and tert-butyl methacrylate monomers by grafting from polythiophene backbone, followed by hydrolysis. The resulting polymer exhibits aqueous solubility via formation of small-sized miceller aggregates with hydrophobic polythiophene at the center and radiating polyionic side chains (cationic or anionic depending on the pH of the medium) at the outer periphery. The critical micelle concentration of PTP in acidic solution (0.025 mg/mL, pH = 2.7) is determined from fluorescence spectroscopy. PTP exhibits reversible fluorescence on and off response in both acidic and basic medium with the sequential addition of differently charged ionic surfactants, repeatedly. The fluorescence intensity of PTP at pH 2.7 increases with the addition of an anionic surfactant, sodium dodecyl benzenesulfonate (SDBS), due to the self-aggregation forming compound micelles. The fluorescence intensity of these solutions again decreases on addition of a cationic surfactant, cetyltrimethylammonium bromide (CTAB), because of assembling of SDBS with CTAB, thus deassembling the PTP-SDBS aggregates. At pH 9.2, these turn on and turn off responses are also shown by PTP with the sequential addition of cationic surfactant (CTAB) and anionic surfactant (SDBS), respectively. This result shows that PTP has potential for surfactant-induced reversible fluorescence turn on and off using ionic surfactant (SDBS and CTAB) through self-assembling and deassembling of the ionic aggregates. The reversible aggregation and disaggregation process of PTP with the surfactants at both acidic and basic pH is supported from dynamic light scattering and Fourier transform infrared spectroscopy. The morphology of the above systems studied by transmission and scanning electron microscopy also supports the above aggregation and disaggregation process. [ABSTRACT FROM AUTHOR]

The selective engineering of conjugated polyelectrolyte (CPE)-phospholipid interfaces is poised to play a key role in the design of advanced biomedical and biotechnological devices. Herein, we report a strategic study to investigate the relationship between the charge of the CPE side group and their association with zwitterionic phospholipid bilayers. The interaction of dipalmitoylphosphatidylcholine (DPPC) phospholipid vesicles with a series of poly(thiophene)s bearing zwitterionic, cationic, or anionic terminal groups (P3Zwit, P3TMAHT and P3Anionic, respectively) has been probed. Although all CPEs showed an affinity for the zwitterionic vesicles, the calculated partition coefficients determined using photoluminescence spectroscopy suggested preferential incorporation within the lipid bilayer in the order P3Zwit > P3Anionic » P3TMAHT. The polarity probe Prodan was used to further qualify the position of the CPE inside the vesicle bilayers via Förster resonance energy transfer (FRET) studies. The varying proximity of the CPEs to Prodan was reflected in the Stern-Volmer quenching constants and decreased in the order P3Anionic > P3TMAHT » P3Zwit. Dynamic light scattering measurements showed an increase in the hydrodynamic diameter of the DPPC vesicles upon addition of each poly(thiophene), but to the greatest extent for P3Anionic. Small-angle neutron scattering studies also revealed that P3Anionic specifically increased the thickness of the headgroup region of the phospholipid bilayer. Epifluorescence and atomic force microscopy imaging showed that P3TMAHT formed amorphous agglomerates on the vesicle surface, P3Zwit was buried throughout the bilayer, and P3Anionic formed a shell of protruding chains around the surface, which promoted vesicle fusion. The global data indicate three distinctive modes of interaction for the poly(thiophene)s within DPPC vesicles, whereby the nature of the association is ultimately controlled by the pendant charge group on each CPE chain. Our results suggest that charge-mediated self-assembly may provide a simple and effective route to design luminescent CPE probes capable of specific localization within phospholipid membranes. [ABSTRACT FROM AUTHOR]

New hybrid-type poly(3,4-ethylenedioxythiophene) (PEDOT) actuators produced by the film-casting method, in which both electrostatic double-layer (EDLC) and faradaic capacitors (FCs) occur simultaneously, have been developed. The electrochemical and electromechanical properties of PEDOT:poly(4-styrenesulfonate) (PSS), PEDOT:PSS/ionic liquid (IL), and PEDOT:PSS/single-walled carbon nanotubes (SWCNTs)/IL actuators are compared with those of a conventional poly(vinylidene fluoride)-co-hexafluoropropylene (PVdF(HFP))/SWCNT/IL actuator. It is found that the PEDOT:PSS/SWCNT/IL actuator provides a better actuation strain performance than a conventional (PVdF(HFP))/SWCNT/IL actuator, as its electrode is an electrochemical capacitor (EC) composed of an EDLC and FC. The PEDOT:PSS polymer helps produce a high specific capacitance, actuation strain, and maximum generated stress that surpass the performance of a conventional PVdF(HFP) actuator. The flexible and robust films created by the synergistic combination of PEDOT and SWCNT may therefore have significant potential as actuator materials for wearable energy-conversion devices. A double-layer charging kinetic model was successfully used to simulate the frequency dependence of the displacement responses of the PEDOT:PSS/IL and PEDOT:PSS/SWCNT/IL actuators. [ABSTRACT FROM AUTHOR]

The ability to control nanoscale morphology and molecular organization in organic semiconducting polymer thin films is an important prerequisite for enhancing the efficiency of organic thin-film devices including organic light-emitting and photovoltaic devices. The current "top-down" paradigm for making such devices is based on utilizing solution-based processing (e.g., spin-casting) of soluble semiconducting polymers. This approach typically provides only modest control over nanoscale molecular organization and polymer chain alignment. A promising alternative to using solutions of presynthesized semiconducting polymers pursues instead a "bottom-up" approach to prepare surface-grafted semiconducting polymer thin films by surface-initiated polymerization of small-molecule monomers. Herein, we describe the development of an efficient method to prepare polythiophene thin films utilizing surface-initiated Kumada catalyst transfer polymerization. In this study, we provided evidence that the surface-initiated polymerization occurs by the highly robust controlled (quasi-"living") chain-growth mechanism. Further optimization of this method enabled reliable preparation of polythiophene thin films with thickness up to 100 nm. Extensive structural studies of the resulting thin films using X-ray and neutron scattering methods as well as ultraviolet photoemission spectroscopy revealed detailed information on molecular organization and the bulk morphology of the films, and enabled further optimization of the polymerization protocol. One of the remarkable findings was that surface-initiated polymerization delivers polymer thin films showing complex molecular organization, where polythiophene chains assemble into lateral crystalline domains of about 3.2 nm size, with individual polymer chains folded to form in-plane aligned and densely packed oligomeric segments (7-8 thiophene units per each segment) within each domain. Achieving such a complex mesoscale organization is virtually impossible with traditional methods relying on solution processing of presynthesized polymers. Another significant advantage of surface-confined polymer thin films is their remarkable stability toward organic solvents and other processing conditions. In addition to controlled bulk morphology, uniform molecular organization, and stability, a unique feature of the surface-initiated polymerization is that it can be used for the preparation of large-area uniformly nanopatterned polymer thin films. This was demonstrated using a combination of particle lithography and surface-initiated polymerization. In general, surface-initiated polymerization is not limited to polythiophene but can be also expanded toward other classes of semiconducting polymers and copolymers. [ABSTRACT FROM AUTHOR]

Advances in polymer chemistry resulted in substantial interest to utilize their diverse intrinsic advantages for biomedical research. Especially, studies on drug delivery for tumors have increased to a great extent. In this study, a novel fluorescent graft copolymer has been modified by a drug and targeting moiety and the resulting structure has been characterized by alterations in fluorescent intensity. The polythiophene based hybrid graft copolymer was synthesized by successive organic reactions and combination of in situ N-carboxy anhydride (NCA) ring opening and Suzuki coupling polymerization processes. Initially, targeted delivery of the graft copolymer was investigated by introducing a tumor specific ligand, anti-HER2/neu antibody, on the structure. The functionalized polymer was able to differentially indicate HER2-expressing A549 human lung carcinoma cells, whereas no signal was obtained for Vero, monkey kidney epithelial cells, and HeLa, human cervix adenocarcinoma cells. After integrating paclitaxel into the structure, cell viability, cell cycle progression, and radiosensitivity studies demonstrate HER2/neu targeting polymers were most effective to inhibit cell proliferation. Importantly, the graft copolymer used had no cytotoxic effects to cells, as evidenced by cell viability and cell cycle analysis. This work clearly confirms that a specially designed and fabricated graft copolymer with a highly complex structure is a promising theranostic agent capable of targeting tumor cells for diagnostic and therapeutic purposes. [ABSTRACT FROM AUTHOR]

We report on the limiting conditions for ion-transfer voltammetry between an ion-exchanger doped and plasticized poly(vinyl chloride) (PVC) membrane and an electrolyte solution that was triggered via the oxidation of a poly(3-octylthiophene) (POT) solid-contact (SC), which was unexpectedly related to the thickness of the POT SC. An electropolymerized 60 nm thick film of POT coated with a plasticized PVC membrane exhibited a significant sodium transfer voltammetric signal whereas a thicker film (180 nm) did not display a measurable level of ion transfer due to a lack of oxidation of thick POT beneath the membrane film. In contrast, this peculiar phenomenon was not observed when the POT film was in direct contact with an organic solvent-based electrolyte. This evidence is indicative of three key points: (i) the coated membrane imposes a degree of rigidity to the system, which restricts the swelling of the POT film and its concomitant p-doping; (ii) this phenomenon is exacerbated with thicker POT films due to an initial morphology (rougher comprising a network of large POT nanoparticles), which gives rise to a diminished surface area and electrochemical reactivity in the POT SC; (iii) the rate of sodium transfer is higher with a thin POT film due to a smoother surface morphology made up of a network of smaller POT nanoparticles with an increased surface area and electrochemical reactivity. A variety of techniques including cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), ellipsometry, scanning electron microscopy (SEM), atomic force microscopy (AFM), and synchrotron radiation-X-ray photoelectron spectroscopy (SR-XPS) were used to elucidate the mechanism of the POT thickness/POT surface roughness dependency on the electrochemical reactivity of the PVC/POT SC system. [ABSTRACT FROM AUTHOR]

Detection of carbon dioxide (CO2) is of fundamental importance in diverse applications ranging from environmental analysis to agricultural production. In this work, a hybrid probe based on guanidinium-pendent oligofluorene (G-OF) and water-soluble conjugated polythiophene (PTP) has been developed for the turn on detection of CO2 with low background signal, taking advantage of the efficient fluorescence quenching of the tight aggregate of G-OF/PTP. In the presence of CO2, the electrostatic repulsion between G-OF and PTP can be effectively enhanced through protonation of the side chains, leading to the disaggregation and thus the "turn-on" fluorescence. The strategy allows for the light-up visible detection of CO2 with high sensitivity. Importantly, this system is capable of sensitively monitoring the concentration changes of CO2 in the process of the photosynthesis, which represents a concept to monitor the photosynthesis based on water-soluble conjugated polymers. [ABSTRACT FROM AUTHOR]

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonic acid) (PEDOT:PSS) is a material consisting of two oppositely charged polymers and is available as aqueous dispersions. Various annealing and doping methods dramatically enhance PEDOT:PSS conductivity, rendering it competitive with inorganic conductors like indium tin oxide. Yet a comprehensive understanding of PEDOT:PSS conductivity enhancement remains elusive. To unravel the chief physical interactions at play, we explore aspects of solution-state PEDOT:PSS through light scattering, X-ray scattering, rheological measurement, and the construction of a partial phase diagram. We show these features in neat water and with the addition of several conductivity enhancement agents: dimethyl sulfoxide, ethylene glycol, 1-ethyl-3-methylimidazolium tetrafluoroborate, or sodium chloride. We find that PEDOT:PSS solutions exist as a dispersion of charged, many-chain microgels with structural features and dynamics strongly influenced by electrostatic interactions. Two distinct phase transitions occur with high sensitivity to ionic strength: a coexistence of a dilute and a concentrated PEDOT:PSS phase and a physical gelation. Despite the rich solution properties uncovered here, we find no connection between them and the enhancement of film conductivity. [ABSTRACT FROM AUTHOR]

Transient hole-burning and resonantly enhanced Raman spectroscopies are used to probe heterogeneities among localized singlet excitons of poly(3-hexylthiophene) in solution. Transient hole-burning spectroscopy facilitated by population dumping through wavelength-selective stimulated emission exposes inhomogeneous broadening of the exciton absorption band in the near-infrared, as reflected by correlations between stimulated emission and excited-state absorption transition energies. Dump-induced spectral diffusion of the exciton absorption band reflects structural fluctuations in the locally excited polymer. This diffusion is observed to occur slightly faster or slower than the nonequilibrium relaxation that follows direct excitation of the polymer (8-9 ps), with the time scale for diffusion varying with subpopulation: dumping across small vs large band gaps results in diffusion over 5 vs 35 ps, respectively. Furthermore, incomplete spectral relaxation of transient holes reflects that subsets of locally excited structural motifs prepared through photoexcitation cannot interchange through structural fluctuations that occur over the singlet-exciton lifetime. Raman spectra of the CC/C-C stretching region collected in resonance at energies across the exciton absorption band exhibit frequency and intensity trends (Raman "dispersion") ascribed to variation in the local effective conjugation length. Together, results explicitly reveal heterogeneities among excitonic states associated with variations and fluctuations in local conformational order. [ABSTRACT FROM AUTHOR]

Hybrids of ethylenediamine-modified reduced graphene oxide (RGO) and polythiophene (PTh) were synthesized successfully by in situ chemical polymerization at room temperature for 2 h and loaded on a flexible PET film to construct a smart sensor. The structure and properties of the hybrids have been characterized by XRD, SEM, TG, UV-vis, and FTIR analysis. The NO2-sensing performance of pure PTh- and hybrids-based sensors was examined at room temperature, the results indicate that the hybrid film sensor with 5 wt % RGO not only exhibits high sensitivity to 10 ppm of NO2 gas which is nearly 4 times higher than that of pure PTh and excellent selectivity but also is flexible, low cost, portable, and wearable. The mechanism of sensing performance enhanced by incorporating graphene into PTh also was discussed, which is attributed to large specific surface of the hybrid and synergetic effects between the components in a hybrid. [ABSTRACT FROM AUTHOR]

The large majority of semiconducting polymers based on poly(alkylthiophene)s with either linear or branched alkyl side chains are reported to p-stack in their crystalline phases. In regioregular poly(3-(2,5-dioctylphenyl)thiophene) (PDOPT), however, p-p interactions are absent due to the presence of the bulky 2,5-dioctylphenyl side groups. In this work, high levels of crystallinity and orientation are created in thin films of PDOPT aligned on substrates of naphthalene by slow directional epitaxial crystallization of the side chains. Depending on molecular weight, both edge-on and flat-on lamellar crystals are obtained. As for poly(3-hexylthiophene) (P3HT), electron microscopy imaging reveals a transition from extended to folded chain crystallization in PDOPT for Mn ~12.7 kDa. The high orientation and crystallinity result in high anisotropy in UV-vis absorption and photoluminescence with well-defined vibronic structures. The single-crystal-like electron diffraction patterns are further used to refine a structural model of PDOPT (a = 29.09 Å, b = 10.45 Å, c = 7.72 Å, a = ß = γ = 90°, and space group P21/c). Uniquely, crystalline PDOPT features perfectly planarized chains despite the absence of p-stacking between polythiophene backbones. The octyl side chains are interdigitated and crystallize in a dense subcell which is compared to that of other semiconducting polythiophenes, e.g. form I poly(3-hexylthiophene) and poly(2,5-bis(3-dodecyl-2-yl)thieno[3,2-b]thiophene), to draw a trend between overall crystallinity and density of the side chain packing. [ABSTRACT FROM AUTHOR]

Based upon a former study, the chlorite-trithionate reaction can avoid the side reactions arising from the well-known alkaline decomposition of polythionates, making it a suitable candidate for investigating spatial front instabilities in a reaction-diffusion-convection system. In this work, the chlorite-trithionate reaction was investigated in a Hele-Shaw cell, in which fingering patterns were observed over a wide range of reactant concentrations. A significant density increment crossing the propagating front indicates that the fingering pattern is generated as a consequence of the buoyancy-driven instability due to the density changes of solute when the gap thickness is less than 4 mm. The velocity of the steepest descent in the propagating front depends almost linearly on the gap thickness but displays a saturation-like profile on the trithionate concentration as well as a maximum on the chlorite concentration. Numerical simulation using the Stokes-Brinkman Equation coupled to the reaction-diffusion processes, including hydrogen ion autocatalysis and consumption, reproduces the observed fingering fronts. [ABSTRACT FROM AUTHOR]

We present a strategy for tuning physical properties of P3HT-based copolymers by incorporating a fluorinated thiophene repeat unit. The synthesis and characterization of a series of fluorinated polythiophene P(3HT-co-3H4FT) materials are described, where the percentage of fluorinated repeat units in the polymer backbone is systematically varied from 0 to 100%. These P(3HT-co-3H4FT)s (P0, P25, P50, P75, and P100) were synthesized via direct arylation polymerization (DArP) methods. By varying the feed ratio of the two monomers, the percent of fluorinated repeat units (3H4FT) could be precisely controlled. As fluorination is increased, there is a strong effect on the electronic properties of the polymers, evidenced by a 0.4 eV drop in the EHOMO level for P100 when compared to P0. GIWAXS and TEM were used to determine the crystallinity and morphology. TEM analysis of thin film polymer/PCBM bulk-heterojunction blends indicates that increased fluorination does not result in stronger phase separation. Organic photovoltaic devices were fabricated to evaluate changes in device performance as a result of fluorination. [ABSTRACT FROM AUTHOR]

Here, taking a polythiophene derivative (PBDD4T) as a starting polymer, we tried to increase the rotation barrier and hence stabilize its backbone conformation by introducing fluorine into the β- and β'-position of the α-linked bithiophene segments and then synthesized a new polymer named as PBDD4T-2F. Our results demonstrate that the rotation barrier between the α-linked bithiophene significantly increases after the fluorination, so PBDD4T-2F has a more stable backbone conformation than PBDD4T. Compared to PBDD4T, PBDD4T-2F shows stronger aggregation effect in solution state and more compact π-π stacking in solid thin film and also possesses deeper HOMO level. These properties make PBDD4T-2F being an ideal donor material in PSCs. When blended with PC71BM, a fullerene acceptor, the PBDD4T-2F-based device showed a power conversion efficiency (PCE) of 9.04%, which is 38% higher than that of the PBDD4T-based device; when blended with ITIC, a non-fullerene acceptor, the PBDD4T-2F-based device showed a PCE of 8.69%, which is almost 20 times higher than that of the PBDD4T-based device. What is more, the tandem cell, in which the blend of PBDD4T-2F:PC61BM was used for making the front subcell, exhibited a high PCE of 10.12%. The photovoltaic results indicate that the fluorination is an effective method to enhance interchain π-π interaction for the polythiophene and hence to tune its photovoltaic properties in PSCs, especially for the fullerene-free device based on ITIC. [ABSTRACT FROM AUTHOR]