Synthesis and morphological characterization of a new conjugated polymer based on benzobisoxazole and thiophene systems

Abstract

In the present work, the synthesis, electropolymerization and polymer characterization of 2,6-di(4-butylphenyl)-4,8-dithiophenylbenzobisoxazole are reported. The synthesis involves several steps from 1,4-benzoquinone to form 2,5-diamine-3,6-dibromohydroquinone, which is condensed with 4-butylbenzoyl chloride and later with thiophen-2-ylmagnesium bromide through Kumada coupling reactions. This monomer is polymerized by potentiodynamic cyclic voltammetry. The voltammograms show a dependency on the range of applied potential, and three different processes of thermodynamically reversible oxidation and reduction occur on a platinum surface. Theoretical calculations are used to characterize these redox processes. The distribution of the frontier orbital density for the monomer and trimer forms show the participation of the thiophene ring in the polymerization processes and partial oxidation of the benzoxazole fragment. The characterization of the polymeric deposit was carried out by scanning electron microscopy and Raman spectroscopy. A dependence of both the morphology and vibrational state of the polymer on the potential range applied exists. This is attributed to the different conformations and dihedral angles of the macromolecule. Finally, the optical properties of the material indicate the existence of intramolecular charge transfer through the system’s thiophene and benzobisoxazole (donor and acceptor).