Poly-N-phenylpyrrole

The quest for new suitable materials represents a similar trend in the development of the solid-phase microextraction (SPME) techniques. Polypyrrole and poly N-phenylpyrrole films exhibit better selectivity toward polar, aromatic, and basic pesticides, due to their inherent multifunctional properties. Their high surface areas (also revealed by scanning electron microscopy) are responsible for the high extraction efficiencies shown by these materials. Mixtures of divinyl-benzene, carboxen, and polydimethylsiloxane-based... 

The morphology of the polymer has, at times, a profound effect on its conductivity or electron-transfer characteristics. When a uniform layer with a small grain size is desired, pretreatment of the electrode surface with acid before electropolymerization has been proven to be effective in the deposition of polypyrrole( toluene sulfonate) on mild steel (S), while the aqueous method for production of poly-3-methylthiophene from acidic aqueous solution mentioned above also has the benefit of producing very uniform (3-4 pm) particles (4J. Uniformity in grain size is also a function of die deposition method. For both 3-methyl thiophene and for ppolypyrrole, use of a brief potential step in the presence of sinall anionic species for production of the polymer has r ulted in a production of a dense, uniform film (9, lOJ, A very thin uniform layer of polymer with an poly (N-phenylpyrrole) sur ce has been obtained by electropolymerization of 4-... 

Derivatives of PPy have also been investigated and some copolymers made. Films of poly-N-methylpyrrole have conductivities much lower than PPy, while film produced from mixtures of pyrrole and N-methylpyrrole have conductivities that vary with composition over five orders of magnitude. The size of any substituent group plays a part in determining the ultimate conductivity of the films, and may even inhibit film formation. For example, poly-N-phenylpyrrole and poly-N-butylpyrrole have reduced conductivities in the range of 0.1-1 S m , while with bulky substituents such as t-butyl and cyclohexyl, brown-black powdery products are obtained instead of films. As with other materials, graft copolymers of PPy have been made by the electrochemical oxidation of pyrrole in the presence of a chain that had been initially modified with a pendant pyrrole unit [43]. 

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