Comparative Survey of Conducting Polymers Containing Benzene, Naphthalene, and Anthracene Cores: Interplay of Localized Aromaticity and Polymer Electronic Structures

Abstract

We present a systematic study to understand to what extent the localization of aromaticity in an orthogonal sense to the main polymer conjugation pathway will influence the observed optical and electrical properties as the polymers undergo oxidation and doping into conductive materials. Three classes of electropolymerizable monomers were prepared where the critical electronic unit was chosen to foster different degrees of aromatic localization pendant to the conjugation pathway: specifically, those based upon benzene, naphthalene, and anthracene cores. The expectation was that the benzene unit would foster extensive intramolecular delocalization upon adoption of the quinoidal electronic structure on account of the strong polyene character. On the other hand, resonance contributors can be rationalized for naphthalene and anthracene whereby one or two aromatic sextets evolve within the quinoidal structure thereby leading to a more localized electronic structure. Monomer and polymer electronics were probed with UV-vis spectroscopy and cyclic voltammetry as well as through in situ profiling of the conductive states of the respective polymers. A semiempirical analysis of the frontier orbital wave functions was employed to further understand the influences of competing aromaticity pendant to the polymer backbones. Our findings indicate the potential for complex and tunable pi-conjugated polymers whose properties can be externally controlled through local alterations of aromatic character within units fused or cross-conjugated to polymer main chains.