Electrochemical synthesis of soluble poly(9-hexylfluorene) and poly(1-hexylindene)

Electrochemical oxidation of 9-hexylfluorene and 1-hexylindene in 0.1 mol dm–3 Bu4NBF4–nitromethane affords π-conjugated polymers, PHF and PHI, respectively, which are fusible and soluble in common organic solvents. Electrode materials affect the formation of the polymers significantly; the molecular weight of PHF increases in the order, glassy carbon (GC) < indium–tin oxide (ITO)⩽ SnO2, and that for PHI, SnO2 GC < ITO. 1 H NMR and IR spectra of the polymers indicate that PHF and PHI comprise mainly linkage of 1,4-fluorenylene and 2, 4-indenylene units, respectively. PHF undergoes a reversible oxidation reaction in acetonitrile, whereas electrochemical oxidation of PHI is irreversible. The electrical conductivities of PHF and PHI doped with SO3 are 10–5 and 10–6 S cm–1, respectively, at room temperature.