Morphology of a self-doped conducting oligomer for green energy applications

JF Franco-Gonzalez and E Pavlopoulou and E Stavrinidou and R Gabrielsson and DT Simon and M Berggren and IV Zozoulenko, NANOSCALE, 9, 13717-13724 (2017).

DOI: 10.1039/c7nr04617k

A recently synthesized self-doped conducting oligomer, salt of bis3,4-ethylenedioxythiophene3-thiophene butyric acid, ETE-S, is a novel promising material for green energy applications. Recently, it has been demonstrated that it can polymerize in vivo, in plant systems, leading to a formation of long-range conducting wires, charge storage and supercapacitive behaviour of living plants. Here we investigate the morphology of ETE-S combining the experimental characterisation using Grazing Incidence Wide Angle X-ray Scattering (GIWAXS) and atomistic molecular dynamics (MD) simulations. The GIWAXS measurements reveal a formation of small crystallites consisting of pi-pi stacked oligomers (with the staking distance 3.5 angstrom) that are further organized in h00 lamellae. These experimental results are confirmed by MD calculations, where we calculated the X-ray diffraction pattern and the radial distribution function for the distance between ETE-S chains. Our MD simulations also demonstrate the formation of the percolative paths for charge carriers that extend throughout the whole structure, despite the fact that the oligomers are short (6-9 rings) and crystallites are thin along the pi-pi stacking direction, consisting of only two or three pi-pi stacked oligomers. The existence of the percolative paths explains the previously observed high conductivity in in vivo polymerized ETE-S. We also explored the geometrical conformation of ETE-S oligomers and the bending of their aliphatic chains as a function of the oligomer lengths.

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