Poly(phenylenevinylene)s ‐ synthesis and redoxchemistry of electroactive polymers

Abstract

AbstractThe development of PPV‐systems has moved from intractable powders to solution processible film‐forming materials by introducing solubilizing phenyl groups. This opens new uses ranging from thin‐film insulators, over photoconductive electrophotographic recording materials, to novel electroactive battery electrodes. In addition, the phenylated PPV may be utilized as a promising thin‐film precursor for microstructured carbon patterns with a stable electrical conductivity (σ = 40 S/cm).PPV is not a metal‐like conductor, but rather a high‐ohmic photoconductor with a band gap of 2.4 eV. It can be made highly conducting upon appropriate chemical or electrochemical treatment (σ= 10−4 − 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).A wide variety of PPV derivatives has been synthesized and characterized by their electrochemical oxidation and reduction potentials. Substituents like phenyl, methoxy and cyano groups have a significant influence on the redox potentials of PPV as the standard polymer (EOx = 0.8 V, ERed = −1.7 V).Thus, for poly(1,4‐phenylene‐1,2‐diphenylvinylene) a broadening of the band gap up to 2.9 eV along with an increase of the oxidation potential up to 1.2 V is estimated.The knowledge of the redox potentials which reflect fundamental properties of conjugated polymers is essential for theoretical and practical reasons.