Polypyrrole matrix, electrochemical polymerization

A similar catalytic activity with a monomeric porphyrin of iridium has been observed when adsorbed on a graphite electrode.381-383 It is believed that the active catalyst on the surface is a dimeric species formed by electrochemical oxidation at the beginning of the cathodic scan, since cofacial bisporphyrins of iridium are known to be efficient electrocatalysts for the tetraelectronic reduction of 02. In addition, some polymeric porphyrin coatings on electrode surfaces have been also reported to be active electroactive catalysts for H20 production, especially with adequately thick films or with a polypyrrole matrix.384-387... 

Polypyrrole electrochemically polymerized within a matrix resin electrically conducting material with improved mechanical properties over those of PPy Lindsey Street, 1985... 

Some applications of polypyrrole, such as drug delivery devices, require specific ion transport. Control of the ion transport process requires determination of the identity of the mobile ion, which is complicate by the fact that there are several ions present in the system. Moreover, Shimidzu and co-woiicers [138,139] demonstrated that ion transport in polypyrrole can be modified by the use of polymeric anions as dopants. Miller and Zhou [140] proved that the electrochemical switching of polypyrrole could achieve controlled release of small anions (such as CIO4), while the incorporation of an immobile polyanion (such as polystyrene sulfonate) resulted in cation transport. The polyanions become trapped within the polypyrrole matrix due to their large size and, perhaps more important, their entanglement with the polypyrrole chains. This increases the stability and mechanical strength of polypyrrole and improves electrical conductivity and electroactivity [141,142]. Therefore it has been of significant interest in the polymerization of pyrrole in polyanion electrolyte solutions [143,144]. 

Novel conductive composite films have been developed by Kaplin and Qutubuddin [101] using a two-step process microemulsion polymerization to form a porous conductive coating on an electrode followed by electropolymerization of an electroactive monomer such as pyrrole. The porous matrix was prepared by polymerizing an SDS microemulsion containing two monomers, acrylamide and styrene [102], The electropolymerization of pyrrole was performed in an aqueous perchlorate or toluenesulfonate solution. The effects of polymerization potential on the electropolymerization, morphology, and electrochemical properties were reported [101]. The copolymer matrix improves the mechanical behavior of the polypyrrole composite film. 

V. Mano and his coworkers studied the conductivity, thermal, mechanical, and electrochemical properties of PVC/polypyrrole blends. The blends were prepared by oxidative chemical polymerization of pyrrole in the vapor phase in PVC films impregnated with FeCl3. l.R. reflectance spectra snggested that the polymerization occnrred preferentially on the matrix snrface prodncing sandwich type structures. DMA studies suggested a certain degree of miscibility among the polymeric components of the blends (88. Mano et al., 1996). 

Enzyme and acid-catalyzed polymerizations Aizawa and Wang have reported that the copper-containing enzyme bilirubin oxidase (BOX) catalyzes the oxidative polymerization of pyrrole to give thin films of polypyrrole on substrates such as glass, plastic or platinum plates. The BOX was first adsorbed onto the matrix support from an aqueous acetate buffer solution (pH 5.5), followed by incubation with the pyrrole monomer (0.2 M) in acetate buffer (pH 6) for several hours at room temperature. The deposited polypyrrole film was reported to have similar properties to PPy made by conventional chemical or electrochemical methods. 

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