Polypyrrole (PPy) is an inherently conducting polymer that has shown great promise for biomedical applications within the nervous system. However, to effectively use PPy as a biomaterial implant, it is important to understand and reproducibly control the electrical properties, physical topography and surface chemistry of the polymer. Although there is much research published on the use of PPy in various applications, there is no systematic study linking the methodologies used for PPy synthesis to PPy's basic polymeric properties (e.g., hydrophilicity, surface roughness), and to the biological effects these properties have on cells. Electrochemically synthesized PPy films differ greatly in their characteristics depending on synthesis parameters such as dopant, substrate and thickness, among other parameters. In these studies, we have used three dopants (chloride (Cl), tosylate (ToS), polystyrene sulfonate (PSS)), two substrates (gold and indium tin oxide-coated glass), and a range of thicknesses, to measure and compare the biomedically important characteristics of surface roughness, contact angle, conductivity, dopant stability and cell adhesion (using PC-12 cells and Schwann cells). As predicted, we discovered large differences in roughness depending on the dopant used and the thickness of the film, while substrate choice had little effect. From contact angle measurements, PSS was found to yield the most hydrophilic material, most likely because of free charges from the long PSS chains exposed on the surface of the PPy. ToS-doped PPy films were tenfold more conductive than Cl- or PSS-doped films. X-ray photoelectron spectroscopy studies were used to evaluate dopant concentrations of PPy films stored in water and phosphate buffered saline over 14 days, and conductance studies over the same timeframe measured electrical stability. PSS proved to be the most stable dopant, though all films experienced significant decay in conductivity and dopant concentration. Cell adhesion studies demonstrated the dependence of cell outcome on film thickness and dopant choice. The strengths and weaknesses of different synthesis parameters, as demonstrated by these experiments, are critical design factors that must be leveraged when designing biomedical implants. The results of these studies should provide practical insight to researchers working with conducting polymers, and particularly PPy, on the relationships between synthesis parameters, polymeric properties and biological compatibility.

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Biocompatibility implications of polypyrrole synthesis techniques.

Solid state dye sensitized solar cells using in situ polymerized PEDOTs as hole conductor

Studies of pollution due to hexavalent chromium are important because it represents a risk to human health and the environment. Hexavalent chromium is a toxic substance and has been found to be carcinogenic. Fortunately, its reduced form, Cr(III), is much less toxic. This paper discusses the remediation Cr(VI) by its reduction in aqueous media by polypyrrole (PPy)-coated reticulated vitreous carbon substrates (RVC). The study is focused on the effect of PPy-film electropolymerization conditions and its efficiency toward the reduction of toxic chromate. We have studied parameters such as the influence of the polymerization electrolyte, the scan rate, the potential limits, and the polymerization cycles concerning the reduction capability of the film. Key results obtained in the present study show that in the presence of different anions during formation of the PPy film, the efficiency of chromate reduction depends on the nature of the anion. We found that the films prepared and treated in the presence of KI...

The Efficiency of Toxic Chromate Reduction by a Conducting Polymer (Polypyrrole): Influence of Electropolymerization Conditions

Photo-sensitizing ruthenium complexes for solid state dye solar cells in combination with conducting polymers as hole conductors

Polypyrrole(dodecylbenzene sulfonate), a type of conjugated polymer that can change volume under electrochemical stimulation, was electrochemically deposited on metal-coated Kapton ® strips using current densities that ranged from 0.4 to 40 mA/cm 2 . The resulting bending beams were subjected to various voltage and current stimulation waveforms, and the beam movements and electrochemical activity were recorded. The extent of beam curling during cyclic voltammetry and potential stepping correlated inversely with deposition current density. However, during current stepping, the curling did not depend on deposition current density. Rather, it depended only on the amount of charge exchanged.

The effects of varying deposition current density on bending behaviour in PPy(DBS)-actuated bending beams

The effects of preparation conditions on the properties of electrochemically synthesized thick films of polypyrrole

Polypyrrole (PPy) films were synthesized under galvanostatic conditions on Pt anodes in a solution of N -methylpyridinium perchlorate in propylene carbonate (PC). The influence of current density, temperature and the amount of water in the reaction mixture on the conductivity and morphology of the prepared PPy films was studied. It was shown that the electrochemical activity of thick PPy films (20 μm) in a solution of 1.0 M LiClO 4 in PC was satisfactory.

M. Vojnoviç

Papers

The effects of preparation conditions on the properties of electrochemically synthesized thick films of polypyrrole

Some aspects of the electrochemical synthesis of polypyrrole