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Synthesis and Characterization of Regiorandom and Regioregular Poly(3-octylfuran)

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journal contribution
posted on 17.02.2001, 00:00 authored by Jeffrey K. Politis, Joel C. Nemes
Poly(3-octylfuran) has been synthesized with three regioregularities:  P3OF-95, P3OF-75, and P3OF-50, where the number signifies the percentage HT content. The 95% HT material is highly crystalline with a structure similar to that of HT-poly(3-octylthiophene), P3OT. The lamellar spacing is 22.1 Å and the π-stacking distance is 3.81 Å. UV−vis spectroscopy reveals that P3OF-95 is aggregated in CHCl3 solution, and solid films of P3OF-95, but not P3OF-75 or -50, show Davydov and exciton band splitting due to the interactions of the π-systems in the stacked morphology. An estimate of the Davydov splitting is 0.15 eV (1200 cm-1). P3OF is reversibly oxidized at 0.32 V vs ferrocene/ferrocenium, but increasing the potential to 1.15 V leads to irreversible oxidation. Films of P3OF may be p-doped with iodine vapor. Doped P3OF-95 and -75 films have electrical conductivities of 10-2 and 10-7 S/cm, respectively. The UV−vis−NIR spectra of the iodine-doped films are interpreted in terms of molecular-like transitions involving the LUMO, HOMO, HOMO-1, and transitions across a Peierls distortion-induced gap in the intermolecular conduction band that is formed by the overlap of the π-systems of the stacked partially oxidized chains. The conduction band gap estimated for P3OF-95 is 0.34 eV, and that for P3OF-75 is 0.9 eV. The P3OF samples are thermally stable in N2 atmosphere to between 275 °C (P3OF-50) and 380 °C (P3OF-95), but suffer thermal oxidation above 150 °C or light-induced oxidation at room temperature.