Aromatic Polymers: Evolution of Their Electronic Properties as a Function of Bond-Length Alternation and Torsion Angle Along the Chains

Abstract

Conjugated polymers based on aromatic rings such as polyparaphenylene (PPP), polypyrrole (PPY), polythiothene (PT), and their derivatives constitute an important class among the polymeric materials that can be made highly conducting upon appropriate chemical or electrochemical treatment [1]. In this paper, we investigate some of the ground-state electronic properties of these compounds. We first study the relationship between the bandgap and the bond-length alternation along the carbon-carbon backbone of the chain [2]. We stress the usefulness of this relationship for designing new organic conjugated polymers with small intrinsic bandnaos [2]. In a second part, we examine how the presence of a torsion angle between adjacent rings along the chains affects ground-state electronic properties such as ionization potential, bandgap, bandwidth, and electron affinity [3]. These are important parameters in the context of the conducting polymer area.