Synthesis and characterization of regiorandom and regioregular poly(3-octylfuran)

Poly(3-octylfuran) has been synthesized with three regioregularities: P3OPF-95, P30F-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 Angstrom and the pi -stacking distance is 3.81 Angstrom. W-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 pi -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 pi -systems of the stacked partially oxidized chains. The conduction band gap estimated for P3OF-95 is 0.34 eV, and that for P30F-75 is 0.9 eV. The P3OF samples are thermally stable in N-2 atmosphere to between 275 degreesC (P3OF-50) and 380 degreesC (P3OF-95), but suffer thermal oxidation above 150 degreesC or light-induced oxidation at room temperature.