M. Jouini

Application of sodium dodecylsulfate (SDS) micellar solution as an organized medium for electropolymerization of thiophene derivatives in water

Abstract Electropolymerization of bithiophene and 3,4-ethylene dioxythiophene has been performed in aqueous SDS solutions on Pt electrode. It has been shown that SDS increases the solubility of both monomers and lowers their oxidation potential. PBT and PEDOT films electrosynthesized in this medium present well-defined structures.

Electrochemical and spectroscopic properties of poly(3-methoxythiophene) electrosynthesized in an aqueous micellar medium

Abstract The electrosynthesis of poly(3-methoxythiophene) (PMOT) was performed on a Pt electrode in an aqueous micellar medium, containing sodium dodecylsulfate (SDS) as surfactant. The resulting PMOT film is electroactive and soluble in several organic solvents. It exhibits electrochemical and IR spectral properties typical of polythiophenes. Mass spectrometry (matrix assisted laser desorption ionization-time of flight or MALDI-TOF) shows that the film is mainly constituted of hexamers. The PMOT UV-Vis absorption and fluorescence spectra reveal remarkably distinct features relative to the monomer.

Anodic oxidation of dipyrrolyls linked with flexible or rigid spacers: study of the electropolymerization mode

Dipyrrolyl monomers with more or less flexible and bulky spacers have been synthesized. The electrochemical behaviour of these monomers and their corresponding polymers has been investigated. Convergent results, obtained by cyclic voltammetry of the monomers and the polymers, ESCA analysis and mass measurements, demonstrate that from an early stage of polymerization, the monomers are oxidized at both pyrrolyl units, leading to different polymer structures, depending on the spacers used.

Catalytic activity of a copper(II)-oxidized glutathione complex on aqueous superoxide ion dismutation

The study of the catalytic activity of a Cu(II)-oxidized glutathione system upon the disproportionation of superoxide radicals shows that the mononuclear complex MA catalyzes dismutation in the pH range 7-9. The corresponding first-order rate constant of value kcat congruent to 6 X 10(6) M-1 sec-1 is pH independent, whereas the second-order rate constant ks for the reference solutions is pH dependent. The kcat constant is about 10-, 100-, and 300-fold higher than the ks constant at pH 7, 8, and 9, respectively. The measured effect is explained in terms of free axial sites in the square-planar arrangement around the copper ion.

Macroscopic modulation of the π-electron density of pendant groups grafted on conductive polymers

Abstract The influence of the redox switching reaction of a conductive polymer upon the π electron density of grafted pendant groups has been studied. Poly( N -phenylpyrrole) and poly( N -benzylpyrrole) have been compared by means of IR spectroscopy and molecular modelling. In the case of poly( N -phenylpyrrole), the evolution of the infrared vibrational bands expresses a reversible modulation of the π electron density of the benzene nucleus when the polymer is switched from its reduced to its oxidized form. There is no such effect when the aromatic moieties are separated from the polymer backbone by a CH 2 group. Moreover, molecular modelling suggests that oxidation of poly( N -phenylpyrrole) makes it possible to break the conjugation between the benzene nuclei and the polypyrrole backbone.

Electrochemical and pH control of the complexation/decomplexation of 4-amino-N,N-diphenylamine with β-cyclodextrin

The behavior of the inclusion complex based on 4-amino-N,N-diphenylamine (ADPA) and cyclodextrin was studied by several techniques at different pH values and in different oxidation states. The results indicate that the reversible inclusion of the guest compound depends on its protonation state, and that its oxidation and reduction occur outside the cyclodextrin cavity. Moreover, the product of the guest bielectronic oxidation reaction is protonated and is free mainly, but in the presence of cyclodextrin and at neutral pH, it fits back into the cavity. This work shows that it is possible to control, by the pH and/or the applied potential, the complexation of ADPA or its oxidation product in a cyclodextrin cavity and gives information for synthesizing encapsulated conductive polymers based on a PANI like structure.

Bithiophene electropolymerization in aqueous media: a specific effect of SDS and β-cyclodextrin

The electrochemical polymerization of bithiophene was performed in water in the presence of either sodium dodecyl sulfate (SDS) or hydroxypropyl-β-cyclodextrin (HPβCD), mainly under potentiostatic conditions. The polymerization process was followed by electrochemical quartz crystal microbalance in order to determine the yield as a function of the current and the potential. Comparable results are obtained in both media (SDS and HPβCD). The polymerization process appears to be critically dependent on the potential and seems to be rate-limited by slow bithiophene diffusion through an interface consisting of accumulated CD or SDS on the electrode surface.

Host-guest complexation : a general strategy for electrosynthesis of conductive polymers

Inclusion compounds using hydroxypropyl-β-cyclodextrin as host molecule have been used to electropolymerize some hydrophobic organic compounds in aqueous medium. This general strategy makes it possible to grow conducting polymers in aqueous medium by anodic oxidation. It is an easy method of obtaining conducting polymers in a very mild manner. Some threaded conducting molecular wire and some water-soluble and processable materials were obtained. Specific conducting polymers which seem to be encapsulated by hydroxypropyl-β-cyclodextrin with some specific inter-chain organization were deposited on solid electrodes.

Polymer chain encapsulation followed by a quartz microbalance during electropolymerization of bithiophene-β-cyclodextrin host–guest compounds in aqueous solution

Abstract Hydroxypropyl-β-cyclodextrins (HPβCD) which form 1:1 host–guest inclusion compounds with bithiophene (BT) are used for the anodic electropolymerization of bithiophene in aqueous solution. Partial encapsulation of the polymer chains by cyclodextrins is suspected from the quartz balance response during polymer reduction by cyclic voltammetry or double-step chronoamperometry. In this case, relatively thin films containing more than one HPβCD molecule for ten BT monomers are formed on platinum electrodes. On the other hand, HPβCD insertion or adsorption in the oxidized form of the polymer, obtained under galvanostatic or potentiostatic conditions, was found to be dependent on experimental conditions (long polymerization time). These results tend to confirm that polymerization occurs outside the CD cavity and that cyclodextrin insertion may occur by chain encapsulation after the polymer formation.

Modulating the electronic properties of pendant groups through the redox switching reaction of a conjugated polymer

In this work we use the switching reaction of conductive polymers as a macroscopic reversible command of the microscopic electronic properties of phenyl nuclei grafted on the polymer backbone. Two approaches, that potentially could enhance the modulation of these electronic properties, are investigated by means of IR spectroscopy: (i) the first consists in diluting the substituents along the polymer backbone by copolymerization of pyrrole and N-phenylpyrrole; (ii) in the second, 1,4-di(N-pyrrolyl)benzene (DPB) homopolymers are used and make it possible to graft two conductive chains on the substituents. It is shown that the first strategy has little impact whereas the second makes it possible to modulate the electronic properties of the benzene nuclei in the opposite direction to that observed with poly(N-phenylpyrrole).