The Peierls Ground State, Solitons and Polarons in Ring-Containing Polymers
Technical rept. 3 Mar 1991-30 Jun 1992,
PENNSYLVANIA UNIV PHILADELPHIA DEPT OF CHEMISTRY
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The report of doping of polyacetylene to form a highly conducting polymer opened the question concerning the nature of the electronic states of the polymer backbone that are formed upon charge transfer between the polymer and dopant backbone. Extensive study of polyacetylene has demonstrated that this system is a degenerate Peierls semiconductor with a bandgap introduced through bond alternation. Pernigraniline is a semiconductor analogous to trans- polyacetylene. However, it differs from polyacetylene in that the overlap between adjacent sites can be modulated by both changes in bond length and changes in ring torsion angle. It is shown that as a result of these two independent order parameters there are differing types of charge excitation possible on pernigraniline backbone, with both bond order excitations such as bond order solitons and ring torsion excitations such as ring torsion polarons possible. Recent photoexcitation spectroscopy studies have confirmed the presence of both bond order solitons and ring rotation polarons.
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