Study of polypyrrole aging by XPS, FTIR and conductivity measurements

Effect of reagent concentrations used to synthesize polypyrrole on the chemical characteristics and optical and electronic properties of the resulting polymer

Nanotubules and nanofibrils of polypyrrole were chemically synthesized using the pores of nanoporous polycarbonate membrane filters as templates. We have previously shown that such “template-synthesized” nanofibrils of polypyrrole can have enhanced conductivities relative to more conventional forms of the polymer (e.g., thin films). Furthermore, we have shown that this enhancement in conductivity is critically dependent on the diameter of the nanofibrils; the narrowest diameter fibrils show the greatest enhancements in conductivity. In this paper we explore the genesis of this enhancement in conductivity by determining the relative conjugation lengths in the polypyrrole fibrils using FTIR and UV−visible−NIR spectroscopies. Using polarized infrared absorption and FTIR spectroscopies, we have followed the evolution of polymer chain orientation and conjugation length with polymer chain growth on the pore wall of the template membrane. On the basis of these results, we have proposed a bilayer model to explain...

Investigation of Molecular and Supermolecular Structure in Template-Synthesized Polypyrrole Tubules and Fibrils.

Single-walled carbon nanotube/polyaniline (SWNT/PANI) composite films were prepared by in situ electrochemical polymerization of an aniline solution containing different SWNT contents. Surface morphology and structural properties of these PANI-based films were examined by a scanning electron microscope and X-ray photoelectron spectroscopy. The electrochemical capacitance properties of these films were investigated with cyclic voltammetry, charge-discharge tests, and ac impedance spectroscopy. The composite film, based on the charge-transfer complex between well-dispersed SWNT and PANI matrixes, shows much higher specific capacitance, better power characteristics, and is more promising for applications in capacitors than a pure PANI film electrode.

Preparation and Electrochemistry of SWNT/PANI Composite Films for Electrochemical Capacitors

The electroactive polymers most commonly studied during the past decade include polyacetylene, polyaniline, polypyrrole, polythiophene, polyphenylene, poly(phenylene sulfide), poly(phenylene vinylene) and some non-conjugated polymers, such as the polyvinylpyridine and poly(N-vinylcarbazole). These polymers along with their analogs and derivatives have been selected to illustrate the type and level of information which can be obtained by the X-ray photoelectron spectroscopic (XPS) technique. It is demonstrated that XPS provides an excellent tool for evaluating the three most important physicochemical properties associated with these polymers, viz., the intrinsic structure, the charge transfer interaction, and the stability and degradation behavior. Some future research directions may involve surface modified or functionalized materials, as well as the application of more surface-sensitive techniques, such as secondary ion mass spectroscopy (SIMS) and scanning tunneling microscopy (STM), which allow us to probe the reactive surfaces and interfaces of the electroactive polymers.

H. S. Munro

Papers

An ESCA study of polypyrole oxidation