Active Polymer Films Research Articles

Fabrication of optically active flexible polymer films with embedded chain-like arrays of silver nanoparticles

We report a straightforward method for preparation of freestanding transparent polymer film containing 2D silver nanoparticle arrays and possessing polarization-sensitive optical properties.

Investigations of organic light emitting diodes with CdSe(ZnS) quantum dots

In this study, we report results on investigation of bilayer light emitting diodes made of organic capped CdSe(ZnS) core/shell type nanocrystals and poly[2-phenyl-3-(9,9-dihexyl-fluoren-2-yl) phenylene vinylene]-co-[2-methoxy-5-(2′-ethylhexyloxy) phenylene vinylene] (FP-PPV-co-MEH-PPV) electroluminescent co-polymer. Light emitting diodes of structure: indium-tin-oxide (ITO)/polyethylene dioxythiophene: polystyrene sulfonate (PEDOT:PSS)/FP-PPV-co-MEH-PPV/Ca/Al devices have been fabricated and studied. The co-polymer device emits a yellow light with a maximum brightness of 3949 cd/m 2 and a maximum external quantum efficiency of 0.27 cd/A at 10 V. Incorporation of CdSe(ZnS) quantum dots into the active polymer film resulted in an increase in device brightness, which reached 8192 cd/m 2 and in external quantum efficiency, which became 1.27 cd/A at 7 V with a lower turn-on voltage. The results indicate that CdSe(ZnS) quantum dots improved significantly the emission of the devices by modifying the injection and transport of the charge carriers. We suggest a non-uniform dispersion of QDs in the co-polymer layer with carrier blocking process by the particles, which produced a balanced charge distribution inside the co-polymer, and thus increased the emission efficiency.

Optically Active Polymer Film Tuned by a Chirally Self‐Assembled Molecular Organogel.

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Distributed-feedback vertical cavity structures for optically pumped solid-state organic lasers

Theoretical analysis of threshold gain and absorption efficiency is presented for a vertical-cavity surface-emitting organic laser by using transfer matrix method. Pyrromethene 567 dye doped in a polymer film is examined for verification of the active material with an InGaN cyan LED as a pump source. By alternately stacking high- and low-refractive-index active polymer films, modeling results indicate that the threshold gain can be reduced and the absorption efficiency at the pump wavelength can be improved compared with those of a vertical cavity with a dielectric mirror stack. The absorption efficiency of the distributed-feedback resonator is not practically degraded even if the pump wavelength is located near the stopband.

Optically active polymer film tuned by a chirally self-assembled molecular organogel

Chirally-oriented lipid aggregates were doped into a solid polymer film, which was readily prepared by casting and removing a solvent from anionic l-glutamide-derived organogels and polystyrene. When a cationic achiral dye was mixed into this system, the resultant polymer film showed tunable circular dichroism (CD) due to chiral complex formation with the achiral dye on the highly-ordered structures based on the l-glutamide lipid.

Modification of Indium−Tin Oxide Electrodes with Thiophene Copolymer Thin Films: Optimizing Electron Transfer to Solution Probe Molecules

We describe the modification of indium-tin oxide (ITO) electrodes via the chemisorption and electropolymerization of 6-{2,3-dihydrothieno[3,4-b]-1.4-dioxyn-2-yl methoxy}hexanoic acid (EDOTCA) and the electrochemical co-polymerization of 3,4-ethylenedioxythiophene (EDOT) and EDOTCA to form ultrathin films that optimize electron-transfer rates to solution probe molecules. ITO electrodes were first activated using brief exposure to strong haloacids, to remove the top approximately 8 nm of the electrode surface, followed by immediate immersion into a 50:50 EDOT/EDOTCA co-monomer solution. Potential step electrodeposition for brief deposition times was used to grow copolymer films of thickness 10-100 nm. The composition of these copolymer films was characterized by solution depletion studies of the monomers and atomic force microscopy (AFM), X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy (reflection-absorption infrared spectroscopy (RAIRS)) of the product films. The spectroscopic data suggest that the composition of the copolymer approaches 80% EDOTCA when electropolymerization occurs from concentrated (10 mM) solutions. AFM characterization shows that electrodeposited poly(EDOT)/poly(EDOTCA) (PEDOT/PEDOTCA) films are quite smooth, with texturing on the nanometer scale. RAIRS studies indicate that these films consist of a combination of EDOTCA units with noninteracting -COOH groups and adjacent hydrogen-bonded -COOH groups. The EDOTCA-containing polymer chains appear to grow as columnar clusters from specific regions, oriented nearly vertically to the substrate plane. As they grow, these columnar clusters overlap to form a nearly continuous redox active polymer film. ITO activation and formation of these copolymer films enhances the electroactive fraction of the electrode surface relative to a nonactivated, unmodified "blocked" ITO electrode. Outer-sphere solution redox probes (dimethylferrocene) give standard rate coefficients, kS > or = 0.4 cm.s-1, at 10 nm thick copolymer films of PEDOT/PEDOTCA, which is 3 orders of magnitude greater than that on the unmodified ITO surface and approaches the values for kS seen on clean gold surfaces.

Polymer bulk homojunction photonic devices

We demonstrate polymer photonic devices based on the formation of multiple p-n junctions within the bulk of the active polymer film. By simple mixing of metallic particles into an electrolyte/electroluminescent composite polymer film, thousands of tiny light-emitting p-n junctions are formed in situ by electrochemical p- and n-doping. This bulk homojunction device exhibits a large active light-emitting area, as well as a giant open-circuit voltage of 25.5V, when operated as a photovoltaic cell. All devices are constructed in an extremely large planar configuration that can be directly imaged with a digital camera.

Morphological and electronic consequences of modifications to the polymer anode ‘PEDOT:PSS’

We present a microscopic and electronic investigation of the polymeric anode poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) used as an electrode in photovoltaic and single carrier diodes. PEDOT:PSS is processed from aqueous solution as a colloidal dispersion with excess PSS present. We modify the PEDOT:PSS solution by the addition of a high boiling point alcohol, glycerol, which is known to increase the conductivity of the spin-coated film. Atomic force microscopy indicates swelling and greater aggregation of the PEDOT-rich colloidal particles found in this system. Current–voltage characteristics of ‘hole-transporting’ diodes, formed with gold contacts, suggest less surface enrichment of PSS in the glycerol modified electrode. Through Kelvin probe microscopy, we find the surface potential of glycerol modified PEDOT:PSS decreases by approximately 0.12 eV, which we assign to a reduction in surface enrichment by PSS. Photovoltaic diodes, using a PFB:F8BT polymer blend as the photo-active layer, and glycerol modified PEDOT:PSS anodes are significantly improved as compared to those with unmodified PEDOT:PSS anodes. This is likely to be due to improved hole-injection from the active polymer film into the PEDOT:PSS anode. This emphasises the electronic consequences of the morphological reorientation of the PEDOT and PSS.

Diffraction gratings and buried nano-electrodes—architectures for organic solar cells

One limiting factor to the efficiency of the bulk heterojunction solar cell is the weak absorbance of the thin photoactive layer. The thickness is restricted by the small charge carrier mobility. Two cell concepts—light trapping with diffraction gratings and buried nano-electrodes—were investigated. Optical simulations based on rigorous coupled wave analysis were performed with supporting experiments in order to evaluate the concept of an embossed diffraction grating in the active polymer film. An increased absorptance in the active layer is calculated for transversal electric polarisation. High losses in the corrugated aluminium electrode in transversal magnetic polarisation would require a displacement of the corrugated boundary between two dielectrics. The second approach is based on vertical nano-electrodes. The planar semi-transparent electrode is substituted by comb-like array of electrodes embedded in the photoactive polymer blend. The potential of this approach is discussed and initial experimental results are presented.

Solid-state electrochromic device based on two poly(thiophene) derivatives

A solid-state electrochromic device was assembled using a polymer electrolyte and optically transparent electrodes modified with thin films of poly{3-[12-( p-methoxyphenoxy)dodecyl]thiophene} and poly(3,4-ethylenedioxythiophene) doped with poly(styrenesulfonate). Poly(epichlorohydrin-co-ethylene oxide) containing LiClO 4 was used as the polymer electrolyte. After assembling, the device was studied by spectroelectrochemical techniques. The best performance of this device could be obtained by adjusting the relative thickness of the active polymer films and the potential range of operation of the device. The device shows color variation during ca. 500 charge/discharge cycles and can be constructed under atmospheric conditions. The results obtained suggest a multitude of perspectives in applications in electrochromic displays.

Two-step inflation of cellular polypropylene films: void-thickness increase and enhanced electromechanical properties

In cellular, electromechanically active polymer films, the so-called ferroelectrets, the cell size and shape distributions can be varied through a controlled inflation process. Up to now, high-pressure treatments were usually performed at elevated temperatures. There are, however, significant experimental limitations and complications if the pressure and temperature treatments are performed at the same time. Here, we demonstrate the controlled inflation of cellular polypropylene films by means of separate pressure and temperature treatments. Separate procedures are much easier to implement. Excellent electromechanical properties were achieved with such a two-step inflation process. The technique has significant potential for inflating large-area transducer films for electromechanical and electroacoustical applications.

Redox sensing of anions in pure aqueous environment by ferrocene-containing 4,4′-bipyridinium-based receptors and polymer films

Selective voltammetric sensing of ATP(2-) anions in water was achieved using ferrocene-viologen based redox active receptors and related polymer films.

Electrochemical impedance spectroscopy of thin films with two mobile charge carriers: effects of the interfacial charging

In the electrochemical systems containing an excess of the background electrolyte, the faradaic process and the interfacial (‘double-layer’) charging are coupled to the fluxes of different charge carriers, the former being related to the diffusional transport of electroactive entities while the latter being realized mostly by ions of the supporting electrolyte. As a result, the interfacial capacitance Cdl may simply be added in parallel to the faradaic impedance specific for each particular system (Randles & Ershler). This simple treatment is not justified in the absence of an indifferent electrolyte, if the same charged species take part in both the electrode reaction and the double layer charging. This is the case where at least one of the ions of a binary electrolyte participates in the electron transfer process or cross the interface. A similar situation arises in the case of an electrochemically active polymer film in that mixed electronic–ionic conductivity prevails, i.e. the charging of the polymer (electron transport) is accompanied by the motion of the charge-compensating counterions (or co-ions). In such systems both interfacial processes are coupled with the same flux of the ‘electroactive’ component. Moreover, the distributions of both charged species inside the film are interrelated due to the electroneutrality condition and the self-consistent electric field so that their transport cannot be considered as pure diffusion. This paper presents an analysis of the alternating current passage across a thin film containing mobile charge carriers of two types, which for the sake of specificity are referred to as ‘electrons’ and ‘counterions’ (although the results are also valid for other systems with two charge carriers). The contributions at the interfaces related to the faradaic processes (or the ion exchange) and to the double-layer charging have been taken into consideration ‘ab initio’. Analytical expressions for the complex impedance have been obtained for three principal arrangements of the system, m ∣ f ∣ m′ (film between two electronic conductors), s′ ∣ f ∣ s (‘membrane’, film between two solutions) and m ∣ f ∣ s (modified electrode). Besides the parameters characterizing the transport processes of the charged species in the bulk film, these formulae contain four characteristics of each interface α (α=m ∣ f or f ∣ s), Rα (charge transfer resistance), Cα (interfacial capacitance), teα=1−tiα (‘double-layer numbers’) and Cμα (‘asymmetry factor’). The predicted complex-impedance plots demonstrate a greater variety of shapes compared to those predicted by traditional approaches.

Polymer-modified electrodes with pendant [Rh III(C 5Me 5)(L)Cl] +-complexes formed by γ-irradiation cross-linking

The immobilization of copolymers of hydrophilic N-vinyl-pyrrolidone and polymerizable derivatives of the transition metal complex (pentamethylcyclopentadienyl-2,2′-bipyridine chloro) rhodium(III) ([Rh III(C 5Me 5)(bpy)Cl] +) by γ-irradiation on an electrode surface to obtain swellable and highly permeable redox active polymer films which swell easily is described. These polymer films swell easily in water and thus provide a three-dimensional reaction layer, which should be advantageous for electrocatalytic processes mediated by the surface-confined rhodium complex. Rotating disk voltammetry is used to investigate the influence of radiation dose and the amount of immobilized polymer on the permeability of the polymer films. Furthermore, cyclic voltammograms show that the rhodium complex retains its electrochemical activity and also its ability to mediate the electrochemical reduction of the cofactor nicotinamide adenine dinucleotide (NAD +).

Electropolymerization of 2-hydroxy-3-aminophenazine (HAPh): properties of pHAPh films and kinetics of oxidation and incorporation of dihydroxybenzenes at Pt/pHAPh electrodes

2-Hydroxy-3-aminophenazine (HAPh) gives stable redox active polymer (pHAPh) films after oxidative electropolymerization on Pt, Au, glassy carbon and ITO electrodes. pHAPh is a new ladder polymer with structures and redox properties closely related to those of poly( o-phenylenediamine) and poly( o-aminophenol). The electropolymerization of HAPh on Au is accompanied by electrodissolution of the Au substrate. Dissolved Au species are redeposited producing dispersed gold crystallites in the organic polymer film. The pHAPh film can respond to dissolved organic species, such as dihydroxybenzenes and p-benzoquinone, in the electroinactive potential range. For the oxidation of dihydroxybenzenes the rate controlling processes are all three contributory steps, i.e. charge transport and diffusion of substrate within the film and cross-exchange electron transfer reaction between the substrate and the redox sites of the film. For p-benzoquinone, the reduction process is solely governed by substrate diffusion within the film. RRDE measurements have shown that the dihydroxybenzenes are incorporated in the pHAPh film in the reduced state. There is also evidence that p-benzoquinone is also incorporated in the film when it is in the oxidized state.

Anion selective optical sensing with metalloporphyrin-doped polymeric films

Metalloporphyrins (Mn(III) and In(III)] are investigated as active polymer film components in the design of reversible anion-selective optical sensors. The optical measurements are made by casting thin plasticized polymer films (PVC, polyurethane, etc.) containing the given metalloporphyrins on glass plates. When bathed in aqueous test solutions, the optical response of such films is based upon the selective extraction of anions by metalloporphyrins into the organic membrane phase. Changes in optical absorbance occur via either of two mechanisms. For films based on Mn(III) tetraphenylporphyrins, the porphyrin itself can serve simultaneously as the ionophore and chromophore for the detection of iodide ions. In this instance, direct ligation of iodide as an axial ligand of the central (Mn(III) results in a change in the molar absorptivitiy of the soret band of the porphyrin. In the case of In(III) octaethylporphyrin, the incorporation of an appropriate pH-indicator dye along with the metalloporphyrin is required to achieve films with optical selectivity toward nitrite and chloride. The analytical characteristics of these porphyrin-based films with respect to anion response time, dynamic measurement range, and reproducibility, are discussed.

ChemInform Abstract: Electrocatalytic Hydrogenation of Organic Compounds on Carbon Electrodes Modified by Precious Metal Microparticles in Redox Active Polymer Films.

ChemInformVolume 19, Issue 8 Preparative Organic Chemistry ChemInform Abstract: Electrocatalytic Hydrogenation of Organic Compounds on Carbon Electrodes Modified by Precious Metal Microparticles in Redox Active Polymer Films. L. COCHE, L. COCHE Lab. Electrochim. Org., CNRS, Univ. Sci. Technol. Med. Grenoble, 38402 Saint Martin d'Heres, Fr.Search for more papers by this authorJ.-C. MOUTET, J.-C. MOUTET Lab. Electrochim. Org., CNRS, Univ. Sci. Technol. Med. Grenoble, 38402 Saint Martin d'Heres, Fr.Search for more papers by this author L. COCHE, L. COCHE Lab. Electrochim. Org., CNRS, Univ. Sci. Technol. Med. Grenoble, 38402 Saint Martin d'Heres, Fr.Search for more papers by this authorJ.-C. MOUTET, J.-C. MOUTET Lab. Electrochim. Org., CNRS, Univ. Sci. Technol. Med. Grenoble, 38402 Saint Martin d'Heres, Fr.Search for more papers by this author First published: February 23, 1988 https://doi.org/10.1002/chin.198808081Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume19, Issue8February 23, 1988 RelatedInformation

Electrocatalytic hydrogenation of organic compounds on carbon electrodes modified by precious metal microparticles in redox active polymer films

Electrocatalytic hydrogenation of organic compounds on carbon electrodes modified by precious metal microparticles in redox active polymer films