Dependence of Polymer Electronic Structure on Molecular Architecture: Polyacetylenes, Polyphenylenes and Polythienylene

Abstract

Increasingly frequent attempts to prepare conducting polymeric materials via the molecular doping of nominally insulating nonsaturated-backbone polymer matrices has led to recent studies of the electrical properties of doped polyacetylene[(CH)_X](1–4), poly(p-phenylene) [(C₆H₄)_X] (5), poly(2,5-thienylene) [(C₄SH₂)_X] (6), poly(1,6-heptadiyne) ([CH(C₆ H₇)]x)(7), and poly(p-phenylene sulfide) [(C₆H₄-S)_X] (8,9). Consequently, the nature of the electronic states in such materials is a matter of considerable interest, and several different types of models have been proposed to describe these states (10). In the case of the doped polymers, the construction of suitable models for this purpose is hampered severely by the lack of structural information on the positions of the dopants. Even for “pure” polymers, however, the conformations of the macromolecular chains are known precisely only in certain special cases of crystalline (isotactic) materials. Therefore in this paper we report a study of the effects of molecular architecture and conformation on the cation states of model oligomers.