Claude Chevrot

Fully undoped and soluble oligo(3,4-ethylenedioxythiophene)s:spectroscopic study and electrochemical characterization

Fully undoped oligo(3,4-ethylenedioxythiophene)s have been synthesized from polycondensation of the corresponding dibromomonomer in the presence of a catalytic Ni(0)-based complex in N,N-dimethylacetamide (DMA). HPLC analysis indicated that the material is constituted of three main oligomers which have also been clearly detected by UV-Visible spectroscopy. Due to its partial solubility in DMA, processability is improved compared to the corresponding insoluble polymer and thin films of oligomers can be deposited by evaporation. Electrochemical and electrochromic properties of undoped film have been carried out. Deep purple in its undoped state, the material becomes sky blue in the oxidized form. The mixture of oligomers was characterized by means of Raman scattering, IR absorption and X-Ray dffraction (XRD), and compared to the poly(3,4-ethylenedioxythiophene) obtained by the oxidative route.

Synthesis and electrochemical properties of mixed ionic and electronic modified polycarbazole

A carbazole N-substituted by an oxyethylene group was polymerized using oxidative electro-polymerization. Due to the hydrophilic properties of the oligooxyethylene substituent, this monomer can be solubilized and electropolymerized in aqueous electrolyte solution. An acidic medium is particularly appropriate in order to decrease the oxidative potential and to obtain films mainly composed of short oligomers as revealed by GPC analysis. By comparison, the chemical polymerization of the corresponding 3,6 dibromo derivative leads to oligomers with well-defined structure and leads to the obtention of longer macromolecular chains. Electrochromic properties of these materials have been studied and a transition from colorless to deep green has been observed during the oxidation. More particularly interesting are the stability of such materials during polarization and the kinetics of diffusion of the counter ion in the film. In acidic medium 1.25 mol l−1 HClO4, 95% of the charge density was maintained after polarization for 7000 cycles which shows the good electrochemical stability of this material compared with other polycarbazoles. Diffusion coefficient have been evaluated in aqueous media about DClO4−=10−11 cm2 s−1. Moreover, films are electroactive in oxyethylene based electrolytes. Then, they are probably well-compatible with hydrophilic poly(oxyethylene) solid electrolytes such that all-polymer devices may be prepared.

Robust solid polymer electrolyte for conducting IPN actuators

Interpenetrating polymer networks (IPNs) based on nitrile butadiene rubber (NBR) as first component and poly(ethylene oxide) (PEO) as second component were synthesized and used as a solid polymer electrolyte film in the design of a mechanically robust conducting IPN actuator. IPN mechanical properties and morphologies were mainly investigated by dynamic mechanical analysis and transmission electron microscopy. For 1-ethyl-3-methylimidazolium bis-(trifluoromethylsulfonyl)-imide (EMITFSI) swollen IPNs, conductivity values are close to 1 × 10−3 S cm−1 at 25 ° C. Conducting IPN actuators have been synthesized by chemical polymerization of 3,4-ethylenedioxythiophene (EDOT) within the PEO/NBR IPN. A pseudo-trilayer configuration has been obtained with PEO/NBR IPN sandwiched between two interpenetrated PEDOT electrodes. The robust conducting IPN actuators showed a free strain of 2.4% and a blocking force of 30 mN for a low applied potential of ±2 V.

New organic materials for light emitting devices based on dihexylfluorene-co-ethylenedioxythiophene copolymers exhibiting improved hole-injecting properties

We report the synthesis, optical and electrochemical characterisations of 9,9-di-n-hexylfluorene-co-3,4-ethylenedioxythiophene (DHF-coEDOT) copolymers obtained from a mixture, in various ratios, of the two corresponding dibrominated monomers by dehalogenative polycondensation. Elemental analysis, IR studies coupled with 1 H NMR clearly indicate, as expected, that the amount of each monomer unit in the final materials is strongly correlated with the feed composition even though the reactivity of the dibrominated EDOT seems lower than that of dibrominated DHF. It appears that even a low EDOT content, i.e. 11‐15 mol%, within a PDHF main chain, leading to the copolymer COPO1, caused significant changes in the electronic properties of the material when compared to PDHF homopolymer. Higher EDOT contents lead to less soluble copolymers which are not suitable for investigation of their use as luminescent semiconducting p-conjugated materials in organic light emitting diodes (OLEDs). Green organic light emitting devices based on COPO1 have been investigated and showed improved hole injection properties when compared to devices based on PDHF homopolymer. The origin of the emitted light has been attributed to the concomitant emission of aggregates PDHF segments with EDOT short oligomeric segments. The use of an additional poly(3,4-ethylenedioxythiophene-2,5-diyl) (PEDOT)‐polystyrene sulfonate (PSS) layer on the indium tin oxide (ITO) anode has also been investigated and leads to improved operating lifetime. # 2002 Elsevier Science B.V. All rights reserved.

Optical and electrochemical properties of soluble N-hexylcarbazole-co-3,4-ethylenedioxythiophene copolymers

Abstract We synthesised soluble N -hexylcarbazole-co-3,4-ethylenedioxythiophene (HCz-co-EDOT) copolymers from mixtures in various ratio of the two corresponding dihalogenated monomers. From EDOT/HCz starting molar ratio: 0.25, 1, 4, we obtained random copolymers named, respectively, C1, C2 and C3 and we compared their properties to the two homopolymers synthesised in the same way. The Infra red studies clearly indicated, as expected, that an increase in the amount of ethylenedioxythiophene in the feed composition leads to an increase of the proportion of the corresponding comonomer in the final materials. Elemental analysis point out that the reactivity of dibrominated EDOT seems slightly lower than that of dibrominated HCz. Thin films of copolymer have been prepared and their electrochemical response have been investigated. Absorption and luminescence of these materials have been also studied in CHCl 3 . Copolymers mainly composed of one monomer (C1 and C3) behaves like the corresponding homopolymers. On an other hand, copolymer (C2) obtained from an equimolar amount of each monomer in the feed composition clearly exhibits distinct signals in optical spectra and in electrochemical behaviour, probably due to the presence of each monomer unit short segments . So, the use of C2 has been explored for possible application in light emitting devices indicating that the p-doping of the material would be facilitated leading to an improved hole injecting when compared to carbazoles homopolymer. It could be particularly interesting as a hole transporting layer in multilayer organic light emitting devices.

Interfacial polymerization of a 3,4-ethylenedioxythiophene derivative using Langmuir–Blodgett technique. Spectroscopic and electrochemical characterizations

Abstract In this study, we have used an EDT derivative with a tetradecyloxy chain (EDTMC14) that renders the monomer soluble in organic solvents as well as suitable for Langmuir–Blodgett (LB) experiments. EDTMC14 monomer was investigated regarding its spreading and polymerization behavior at the air–water interface. The polymerization at the interface depends on the CAN concentration and pH in the subphase. For comparison, we have studied the behavior of the corresponding polymer (PEDTMC14) obtained by chemical polymerization. The different LB films showed the same characteristics in FTIR spectroscopy and electrochemistry and conductivity measurements. These results may indicate that both polymers have essentially the same molecular structure in the p-doped state, and that the pre-organization of the monomers in the Langmuir films seems to have no dramatic influence on the polymer properties.

Electrosynthesis and oxidation of new oligoazomethines containing N-ethylcarbazole groups

Abstract Oligoazomethines containing the N -ethylcarbazole group have been synthesized by dehalogenative polycondensation of dibromides of N -ethylcarbazole-azomethine as monomer in the presence of electrogenerated zerovalent nickel acting as a catalyst. Chemical oxidation of these new compounds by FeCl 3 was studied by optical spectroscopy and electrochemical oxidation by cyclic voltammetry.

Synthesis and Characterization of IPNs for Electrochemical Actuators

Interpenetrating polymer networks (IPNs) have been developed for many years leading to materials with controlled properties. When an electronic conducting polymer (ECP) is incorporated into an IPN, this one becomes a conducting IPN (CIPN). The synthetic pathway ensures a non homogeneous dispersion of the ECP through the IPN thickness of the material. The system is thus similar to a layered one with the advantage that the intimate combination of the three polymers needs no adhesive interface. The last step in making the CIPN into an actuator is to ensure the ionic conductivity by incorporation of an ionic salt. The highest ionic conductivity through the IPN matrix is necessary in order to ensure the best actuation. The chosen salt is an ionic liquid, i.e. 1-ethyl-3- methylimidazolium bis(trifluoromethylsulfonyl)imide (EMImTFSI). Based on IPN architectures electrochemical actuators have been designed and actuation in open air has been characterized.

Actuation and Sensing properties of Electroactive Polymer Whiskers

Abstract In a world of unknown, touch modality is a key avenue for environments exploration. Implementation of such modality in mobile robot has been a major challenge for many research teams. Recently, several artificial whisker systems have been studied as promising tactile sensor. One key to the whiskers functionality is its sensor system. Our laboratory recently synthesized new electroactive polymer (EAP) actuator/sensor based on interpenetrated polymer networks (IPN) as host matrix and electrically conducting polymer. The first results of such actuator/sensor devices and their integration in a whisker prototype will be presented.

Characterization of a new interpenetrated network conductive polymer (IPN-CP) as a potential actuator that works in air conditions

This paper presents the characterization in terms of force and displacement of a new interpenetrated network conductive polymer (IPN-CP) to be used as an actuator that works in air conditions. This last property opens many potential applications in robotics, bionics, haptics interface technology (namely tactile feedback devices), etc. Different experimental investigations show that the proposed actuator exhibits acceptable force behavior and capabilities (relatively to its size and mass) when classical solvents are used. However, IPN-CP with ionic liquid solvents show poor capabilities. Since ionic solvents guarantee long life usability, we found it somehow disappointing namely for robotic applications. We give some explanations for that, but we believe that this drawback could mid solutions in the near future.