J. E. Frommer

Conducting complexes of polyphenylene sulfides

Poly(p‐phenylene) sulfide, poly(m‐phenylene) sulfide, and the newly synthesized polymer poly(thio‐2,8‐dibenzothiophenediyl) have been treated with strong electron acceptors (AsF5, SbF5) to form conducting complexes with p‐type electronic conductivities up to 3 S/cm. Near IR to UV absorption spectra and temperature‐dependent conductivity measurements suggest a localization of charge carriers even at high doping levels. Elemental analysis and IR spectroscopy demonstrate that heavy exposure to AsF5 causes substantial changes in the backbone structure of these polymers. The dopant appears to predominantly induce the formation of carbon–carbon bonds bridging the sulfur linkages to form thiophene rings. This chemical modification enhances the conductivity of the complex and, in the case of poly(m‐phenylene), is shown to be an actual prerequisite for achieving high conductivity.

An EPR study of the reaction between poly(p‐phenylene sulfide) and electron‐acceptor dopants

EPR spectra for electron‐acceptor doped poly(p‐phenylene sulfide) are reported. The g values obtained from these spectra correspond to an electron density centered around a divalent sulfur radical cation R–S–R. This assignment is supported by corresponding EPR data from an oligomeric model compound φ–S–φ–S–φ (φ=phenyl). The g value of the sulfur‐based radical cation of doped poly(p‐phenylene sulfide) distinctly contrasts the nearly free electron g values obtained from EPR measurements on poly(p‐phenylene) and its oligomer p‐terphenyl.

Structural changes during annealing and during acceptor doping of oriented poly(p-phenylene sulfide)

Abstract Thermally-annealed, melt-formed poly( p -phenylene sulfide), PPS, has a folded-chain, lamellar structure with a repeat period varying from 90 A to 160 A, depending upon the annealing temperature. Local crystalline order develops in the polymer before the onset of extensive lamellar ordering. On doping oriented PPS with AsF 5 , the polymer swells and loses both crystallinity and chain orientation. The absence of crystalline and lamellar reflections in doped PPS probably results from dopant-induced structural disorder and chemical reactions (formation of dibenzothiophene linkages and crosslinking). These structural changes may explain the relative insensitivity of the conductivity of the doped polymer to the degree of crystallinity and orientation in the precursor polymer.

CONDUCTING COMPLEXES OF CONJUGATED POLYMERS: A COMPARATIVE STUDY.

Abstract There are now a number of different polymers which undergo dramatic conductivity increases on exposure to electron donors or acceptors. The discussion here will center on a comparison of the electrical and optical properties of the different systems, with special emphasis on polyphenylenes and polyphenylenesulfides. The very promising results provided by the Valence Effective Hamiltonian (VEH) technique for the valence band electronic structures of a wide range of undoped polymers will provide the framework for a comparison of the various conducting polymer systems. Though PPP clearly has a higher ionization potential and a higher bandgap than PA, the profiles of their optical and electrical properties for the doped systems are very similar. They both would appear to form “simple complexes” on doping. This behavior is in contrast to the PPS system where chemical modification is seen to play an important role in achieving high conductivity on doping. Polymers which undergo chemical modification ma...

Doped Conjugated Polymers: Theory and Experiment

Recent theoretical and experimental work in the conducting polymers area is reviewed. The specific topics to be discussed are: 1) General experimental aspects of the synthesis and doping of conjugated polymers, 2) Electronic properties of doped conjugated polymers, 3) Conducting polymer solutions, 4) Polyacetylene spectroscopy, 5) Theoretical prediction of electronic and electrochemical properties of conjugated polymers and 6) Charged defect formation and transport in doped polymers.