Quantum mechanical investigation of polymer formation from aminophenols

Ortho-, meta- and para-aminophenols have been used as monomers to form different and versatile polymers, for example to immobilize biological macromolecules in electrochemical biosensors. In this work, we present a quantum-mechanical study about these three monomers as a way to elucidate some of the pathways involved in the electropolymerization of such compounds. As observed, the formation of these polymers depends on monomer resonance structure. This was investigated from their electrostatic potential maps and sets of partial atomic charges for all possible structures that must occur in solution during the formation of the polymeric film. Radical-cation calculations and analysis based on the Natural Bond Orbital theory were also performed. The analysis of frontier orbital permitted to suggest that electropolymerization should involve the pairing between radical cations from protonated monomers (reaction in acid media) and their respective conjugated bases (neutral monomers present in equilibrium).