Conducting poly(3,4-ethylenedioxythiophene)-montmorillonite exfoliated nanocomposites

Synthesis and Impedance Spectroscopy of Poly(p-phenylenediamine)/Montmorillonite Composites

Poly(p-phenylenediamine)/montmorillonite (PPDA/MMT) composites were prepared by the oxidative polymerization of monomers intercalated within the MMT gallery, using ammonium peroxydisulfate as an oxidant. The intercalation process was evidenced by X-ray powder diffraction. The FT-IR and Raman spectroscopies revealed that, depending on the initial ratio between monomers and MMT in the polymerization mixture, the polymer or mainly oligomers are created during polymerization. The DC conductivity of composites was found to be higher than the conductivity of pristine polymer, reaching the highest value of 10^-6 S cm^-1 for the optimal MMT amount used during polymerization. Impedance spectroscopy was performed over wide frequency and temperature ranges to study the charge transport mechanism. The data analyzed in the framework of conductivity formalism suggest different conduction mechanisms for high and low temperature regions.

Preparation and Characterization of Montmorillonite/PEDOT-PSS and Diatomite/PEDOT-PSS Hybrid Materials. Study of Electrochemical Properties in Acid Medium

The hybridization of clay minerals with conducting polymers receives great interest for different potential applications, including environmental remediation. This work studies and compares the electrochemical properties of two different clays, montmorillonite (Mont) and diatomite (Diat), and their respective clay/PEDOT-PSS hybrid materials in H2SO4 medium. The hybrid materials were prepared by electropolymerization of EDOT in the presence of PSS. The physico-chemical and electrochemical properties of both clays were analyzed by different techniques, and the influence of the clay properties on electropolymerization and the electroactivity of the resulting clay/PEDOT-PSS hybrids was investigated. Specifically, the Fe2+/Fe3+ redox probe and the oxidation of diclofenac, as a model pharmaceutical emerging pollutant, were used to test the electron transfer capability and oxidative response, respectively, of the clay/PEDOT-PSS hybrids. The results demonstrate that, despite its low electrical conductivity, the Mont is an electroactive material itself with good electron-transfer capability. Conversely, the Diat shows no electroactivity. The hybridization with PEDOT generally enhances the electroactivity of the clays, but the clay properties affect the electropolymerization efficiency and hybrids electroactivity, so the Mont/PEDOT displays improved electrochemical properties. It is demonstrated that clay/PEDOT-PSS hybrids exhibit diclofenac oxidation capability and diclofenac concentration sensitivity.

Charge Storage Properties of Nanostructured Poly (3,4-ethylenedioxythiophene) Electrodes Revealed by Advanced Electrogravimetry

PEDOT nanowires (NWs) directly grown on the conducting electrode of quartz resonators enable an advanced electrogravimetric analysis of their charge storage behavior. Electrochemical quartz crystal microbalance (EQCM) and its coupling with electrochemical impedance spectroscopy (ac-electrogravimetry or AC-EG) were used complementarily and reveal that TBA⁺, BF₄^- and ACN participate in the charge compensation process with different kinetics and quantity. BF₄^- anions were dominant in terms of concentration over TBA⁺ cations and the anion transfer results in the exclusion of the solvent molecules. TBA⁺ concentration variation in the electrode was small compared to that of the BF₄^- counterpart. However, M_w of TBA⁺ is much higher than BF₄^- (242.3 vs. 86.6 g·mol^-1). Thus, TBA⁺ cations' gravimetric contribution to the EQCM response was more significant than that of BF₄^-. Additional contribution of ACN with an opposite flux direction compared with BF₄^-, led to a net mass gain/lost during a negative/positive potential scan, masking partially the anion response. Such subtleties of the interfacial ion transfer processes were disentangled due to the complementarity of the EQCM and AC-EG methodologies, which were applied here for the characterization of electrochemical processes at the PEDOT NW electrode/organic electrolyte interface.

Evaluation of Fe3+fixation into montmorillonite clay and its application in the polymerization of ethylenedioxythiophene

An analysis of the sorption process allowed to establish that Fe³⁺sorption into montmorillonite is a chemical process that involves an exchange of cations from the montmorillonite interstitial space between layers.

Incorporation of a clot-binding peptide into polythiophene: properties of composites for biomedical applications

Biocomposites formed by a pentapeptide (CREKA), which recognizes clotted plasma proteins, entrapped into the poly(3,4-ethylenedioxythiophene) (PEDOT) matrix have been prepared using three very different procedures. X-ray photoelectron spectroscopy analyses indicate that PEDOT-CREKA films, prepared by chronoamperometry in basic aqueous solution (pH = 10.3) and deposited onto a PEDOT internal layer, present the higher concentration of peptide: one CREKA molecule per six polymer repeat units. The surface of this bilayered system shows numerous folds homogeneously distributed, which have been exhaustively characterized by scanning electron microscopy and atomic force microscopy. Indeed, the morphology and topography of such bilayered films is completely different from those of biocomposite-prepared acid aqueous and organic solutions as polymerization media. The impact of the entrapped peptide molecules in the electrochemical properties of the conducting polymer has been found to be practically negligible. In contrast, biocompatibility assays with two different cellular lines indicate that PEDOT-CREKA favors cellular proliferation, which has been attributed to the binding of the peptide to the fibrin molecules from the serum used as a supplement in the culture medium. The latter assumption has been corroborated examining the ability of PEDOT-CREKA to bind fibrin. The latter ability has been also used to explore an alternative strategy based on the treatment of PEDOT-CREKA with fibrin to promote cell attachment and growth. Overall, the results suggest that PEDOT-CREKA is appropriated for multiple biomedical applications combining the electrochemical properties of conducting polymer and the ability of the peptide to recognize and bind proteins.

Preparation and electrochemical catalytic application of nanocrystalline cellulose doped poly(3,4-ethylenedioxythiophene) conducting polymer nanocomposites

Nanocrystalline cellulose doped conducting polymer PEDOT nanocomposites can be prepared through both chemical (right) and electrochemical (left) polymerization methods.