Electrochromic and highly stable poly(3,4-ethylenedioxythiophene) switches between opaque blue-black and transparent sky blue

Electropolymerized three-dimensional randomly branched EDOT-containing copolymers

The potential of 2,2';3,2″-terthiophene (3T) as branching units in 3D copolymers is presented with EDOT as an example comonomer. Branched EDOT/3T polythiophenes were prepared by electropolymerization, and their electrochemical and optical properties are discussed. Two different approaches were employed: (i) the direct electropolymerization of a novel branched thiophene monomer (3TE3) consisting of a 3T core that contains three outer EDOT end groups and (ii) the electrochemical copolymerization of a EDOT/3T mixture in different ratios from [1:1] to [1:10]. Cyclic voltammetric and vis spectrometric experiments show that the EDOT content within the polymer has a strong influence on the electronic properties of the material: with increasing EDOT content, the HOMO-LUMO gap is decreased. To prove copolymer formation of EDOT and 3T, chemically synthesized reference copolymers of EDOT and 3T were prepared by oxidative coupling using FeCl3, and their optical and electronic properties were compared to those of the electrodeposited films. In addition, the copolymer formation is indicated by the comparison of the electrochemical and spectroscopic results with those of the homopolymers P3T and PEDOT.

Solid-state high-throughput screening for color tuning of electrochromic polymers

Diffusion of two monomers and their oxidative copolymerization inside a solid-state gel electrolyte is utilized as a method to match the monomer feed ratio to a color resulting from a conjugated copolymer having a single absorption in the visible region. Here, a combination of two monomers is used to generate a solid-state electrochromic device of any color, except black and green, in the colored state with all other colors going to transmissive sky blue in the bleached state.

Controlling the morphology of conductive PEDOT by in situ electropolymerization: from thin films to nanowires with variable electrical properties

The controlled electrochemical synthesis of poly(3,4-ethylenedioxythiophene) (PEDOT) as a model conjugated polymer is described here. We show that the morphology of electrochemically synthesized PEDOT can be finely tuned directly in a device, by carefully guiding the nucleation and growth processes as well as electromigration phenomena, resulting in structures with variable electrical properties.

Screening conditions for rationally engineered electrodeposition of nanostructures (SCREEN): electrodeposition and applications of polypyrrole nanofibers using microfluidic gradients

A rapid screening method for optimizing electrochemical deposition conditions of polypyrrole (PPy) nanostructures is reported. An electrochemical cell is integrated within a low-cost microfluidic system, in which electrochemical deposition is carried out across a linear concentration gradient of a reaction parameter. The protocol, refered to as the screening of conditions for rationally engineered electrodeposition of nanostructures (SCREEN), allows rapid screening of conditions for the production of specific morphologies by characterizing the electrodeposited samples produced within a chemical gradient. To demonstrate the utility of the SCREEN method, applications in tunable optical coatings and superhydrophobic surfaces are presented.

Significant different conductivities of the two grades of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate), Clevios P and Clevios PH1000, arising from different molecular weights

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is promising to be the next-generation transparent electrode of optoelectronic devices. This paper reports the differences between two commercially available grades of PEDOT:PSS: Clevios P and Clevios PH1000. The as-prepared PEDOT:PSS films from Clevios P and Clevios PH1000 solutions have close conductivities of 0.2-0.35 S cm(-1). Their conductivities can be enhanced to 171 and 1164 S cm(-1), respectively, through a treatment with hydrofluoroacetone trihydrate (HFA). The differences between Clevios P and Clevios PH1000 were studied by various characterizations on PEDOT:PSS aqueous solutions and PEDOT:PSS films. The gel particles are larger in Clevios PH1000 solution than in Clevios P solution as revealed by dynamic light scattering and fluorescence spectroscopy of pyrene in these solutions. These results suggest that PEDOT of Clevios PH1000 has a higher average molecular weight than that of Clevios P. The difference in the molecular weight of PEDOT for the two grades of PEDOT:PSS is confirmed by the characterizations on their polymer films, including atomic force microscopy and temperature dependences of the resistances of as-prepared and HFA-treated PEDOT:PSS films. The different molecular weights of PEDOT also gives rise to significant differences in the electrochemical behaviors of the two grades of PEDOT:PSS, as revealed by the cyclic voltammetry, in situ UV-vis-NIR absorption spectroscopy and potentiostatic transient measurements.

Electric conductivity-tunable transparent flexible nanowire-filled polymer composites: orientation control of nanowires in a magnetic field

Cobalt compound nanowires were dispersed in a transparent nonconductive polymer film by merely stirring, and the film's transparency and electrical conductivity were examined. This composite film is a unique system in which the average length of the nanowires exceeds the film's thickness. Even in such a system, a percolation threshold existed for the electric conductivity in the direction of the film thickness, and the value was 0.18 vol%. The electric conductivity value changed from ∼1 × 10(-12) S/cm to ∼1 × 10(-3) S/cm when the volume fraction exceeded the threshold. The electric conductivity apparently followed the percolation model until the volume fraction of the nanowires was about 0.45 vol %. The visible light transmission and electric conductivity of the composite film of about 1 vol % nanowires were 92% and 5 × 10(-3) S/cm, respectively. Moreover, the electric conductivity in the direction parallel to the film surface did not depend on the amount of the dispersed nanowires, and its value was about 1 × 10(-14) S/cm. Even in a weak magnetic field of about 100 mT, the nanowires were aligned in a vertical and parallel direction to the film surface, and the electric conductivity of each aligned composite film was 2.0 × 10(-2) S/cm and 2.1 × 10(-12) S/cm. The relation between the average wire length and the electric conductivity was examined, and the effect of the magnetic alignment on that relation was also examined.

A Photoelectron Spectroscopy Study of Ethylenedioxythiophene Adsorption on Polycrystalline Gold Surfaces

The interaction between thin films of ethylenedioxythiophene (EDOT) and polycrystalline copper and gold surfaces has been studied using photoelectron spectroscopy. Thick films of EDOT (∼100 Å) have been prepared by vapor deposition onto clean gold surfaces, which were cooled down to a temperature of 170 K during the deposition process. Monolayers were prepared by slowly heating the thick films up to 300 K. At 300 K most of the material has evaporated from the surface and about one monolayer remains chemisorbed on the gold surface. This shows that there is an interaction between EDOT and Au. This chemisorption causes a shift of around -0.5 eV of the binding energies for the core level electrons, presumably because of screening of the core-hole by the metal. An experimental and theoretical analysis of the valence level electrons suggests that two molecular orbitals, localized at the thiophene part of the molecule, are involved in the interaction with the metal atoms of the surface. The most likely orientation of the EDOT molecules is parallel to the Au surface. Upon adsorption the work function is changed from 5.2 eV for the clean gold surface to 4.0 eV for the EDOT monolayer. In the case of EDOT adsorbed on clean copper surfaces, no interaction was observed.

DNA detection using functionalized conducting polymers

A well-defined DNA bioconjugated surface is a key component in the development of efficient biosensor platforms for diseases, ranging from point-of-care detection of pathogens and viruses to personalized diagnostics and medication, as well as for drug discovery, forensics, and food technology. We herein describe a universal and rapid methodology to construct such surfaces based on functionalized conducting polymer thin films. The conducting polymers combine sensing properties with the ability to act as signal transducers for the biorecognition event. We have shown that biosensor designs based on conducting polymers display a number of advantageous features, such as a long-term stability, label-free sensing, fast analysis, and the capability to apply both electrochemical and fluorescent protocols for DNA detection.

Polymeric memory elements and logic circuits that store multiple bit states

The ever-increasing flow of information requires new approaches for high-density data storage (HDDS). Here, we present a novel solution that incorporates the easily accessible polymer poly(3,4-ethylenedioxythiophene) (PEDOT) with multistate memory. The electrical addressable polymer is able to store up to five different memory states, which are stable up to 20 min. The observed memory states are generated by the optical output signature of the PEDOT deposited on indium tin oxide (ITO) coated glass, upon applying specific electrical inputs. Moreover, the demonstrated platforms can be represented by a general logic circuit, which allows the construction of multistate memory, such as flip-flops and flip-flap-flop logic circuits.

Surface orientation of phenyl groups in poly(sodium 4-styrenesulfonate) and in poly(sodium 4-styrenesulfonate):poly(3,4-ethylenedioxythiophene) mixture examined by sum frequency generation vibrational spectroscopy

Sum frequency generation (SFG) vibrational spectroscopy was used to investigate the surface phenyl ring orientations of spin-coated poly(sodium 4-styrenesulfonate) (PSSNa) and of PSSNa in the spin-coated polymer material Baytron P. Baytron P is a commercially available conducting polymer suspension with poly(3,4-ethylenedioxythiophene) (PEDOT) and PSSNa in water, which is widely used in organic electronic devices. SFG spectra collected using different polarization combinations showed that the twist angles for the phenyl groups on the spin-coated PSSNa and Baytron P surfaces were not random; therefore, both the twist and tilt angles needed to be deduced in order to determine their respective phenyl group orientations. Results indicated that on the PSSNa surface, the para-substituted phenyl ring has a tilt angle of 47.5 degrees +/- 5.3 degrees and a twist angle of 58.8 degrees +/- 8.2 degrees. The tilt and twist angles, 48.2 degrees +/- 3.6 degrees and 65.2 degrees +/- 4.0 degrees, respectively, were determined for the Baytron P phenyl ring, which were not very different from those of PSSNa phenyl groups on the surface.

Ion bipolar junction transistors

Dynamic control of chemical microenvironments is essential for continued development in numerous fields of life sciences. Such control could be achieved with active chemical circuits for delivery of ions and biomolecules. As the basis for such circuitry, we report a solid-state ion bipolar junction transistor (IBJT) based on conducting polymers and thin films of anion- and cation-selective membranes. The IBJT is the ionic analogue to the conventional semiconductor BJT and is manufactured using standard microfabrication techniques. Transistor characteristics along with a model describing the principle of operation, in which an anionic base current amplifies a cationic collector current, are presented. By employing the IBJT as a bioelectronic circuit element for delivery of the neurotransmitter acetylcholine, its efficacy in modulating neuronal cell signaling is demonstrated.