Poly(phenylenvinylen); Entwicklung eines elektroaktiven Polymermaterials vom unschmelzbaren Pulver zum transparenten Film

The development of PPV systems has moved from intractable powders to flexible films. This opens new uses as thin film insulation material, as photoconductive electrophotographic recording material, and as novel electrochemical electrode material for polymer batteries. Tractable films were readily achieved either by transformation of a soluble precursor polymer or by introduction of solubilizing phenyl substituents. Contrary to wide-spread expectations PPV is not a metal-like conductor, but rather a broad-band gap photoconductor (Eg = 2,4 eV). However, it can be made highly conducting upon appropriate chemical or electrochemical treatment, thus forming several salt-like redox stages (σ = 10−4 to 103 S/cm). The formation of coexisting polymeric ion radicals (polarons) and diions (bipolarons) is well understood in terms of the concept of chain segment redox reactions (ECS concept). More detailed studies of the phenyl substituent effect show that the electronic properties are not altered drastically, but are modified due to broadening the band gap up to 2,9 eV along with an increase of the oxidation potential. Furthermore, phenyl substitution increases the resistance to heat, and stabilizes the deeply coloured redox stages.