Selection of electroactive copolymers synthesized from 3-octylthiophene/biphenyl at low potentials as precursors for nanostructured thin-film formation

Abstract

Electrically conducting copolymers of 3-octylthiophene and biphenyl in equimolar ratio were synthesized and also homopolymers for comparison reasons by potentiostatic electropolymerization, and the polymers were deposited as coatings. Based on various criteria, a proper copolymer was selected and the homopolymer of poly(3-octylthiophene) (P3OT) for comparison reasons, in order to investigate their ability to prepare nanostructured thin films. The latter were synthesized by spin coating from solutions of the polymers in anisole. The polymers were characterized by proper methods such as size-exclusion chromatography (SEC), scanning electron microscopy/energy-dispersive spectroscopy (SEM/EDAX), X-ray diffraction (XRD), differential scanning calorimetry (DSC), ultraviolet–visible spectroscopy (UV–Vis), dynamic light scattering (DLS), atomic force microscopy (AFM), and cyclic voltammetry including also the determination of the limiting viscosity number [η] and their electrical conductivity (σ). The selected copolymer and the (P3OT) are mainly amorphous having also regions with order, the copolymer is soluble in more solvents, (P3OT) has higher σ, and both polymers form nanostructured thin films containing nanoparticles with ellipsoid morphology. Generally, the copolymers exhibit comparable properties with those of (P3OT); however, they are far cheaper. Besides the novelty to extend electroactive polymers in new application directions such as nanostructured materials, a further novelty consists of a proposed methodology based on the experimental data, in order to estimate different parameters at molecular level, especially for the macromolecules in solution. The energy gap E g (band gap) of the polymers as nanostructured thin films was determined by cyclic voltammetry indicating semiconductor behavior, which was also confirmed by their electrical conductivity.