New precursor method for conducting poly(p-phenylenevinylene)s

Abstract

The photoinitiated elimination of methoxy groups of poly(p-phenylene-1-methoxyethylene) (precursor-1) and poly(2,5-dimethoxy-p-phenylene-1-methoxyethylene) (precursor-2) in the presence of various onium salts and the resulting doping effect on the final poly(p-phenylenevinylene) (PPV) and poly(2,5-dimethoxy-p-phenylenevinylene) (DMPPV) were investigated. The thermal elimination of the methoxy groups from precursor-1 and precursor-2 was catalyzed by onium salts such as triphenylsulfonium hexafluoro-antimonate (TPS-1), triphenylsulfonium hexafluoroarsenate (TPS-2) and triphenylsulfonium hexafluorophosphate (TPS-3). Upon UV irradiation and the followed heat treatment, precursor-1 and precursor-2 containing the onium salts were converted to PPV and DMPPV at 150℃ and 100℃, respectively. The resulting PPV and DMPPV were found doped by the protic acid generated by decomposition of the onium salts upon UV irradiation. Conductivities of thermally obtained PPV and DMPPV were in the range of $10^{-3}-10^{-1}$ S/cm and $10^{-3}-10^0$ S/cm, respectively. Conductivity was found to depend on the concentration of onium salts. The conductivities of the resulting PPV and DMPPV increased with increasing concentration of TPS-1 and TPS-3. To the thin films of precursor-1 and precursor-2 a conventional lithographic procedure was applied and the conductive patterns of PPV and DMPPV doped photochemically were successfully produced in non-conjugated precursor matrix. In case of precursor-2 film, non-conjugated matrix could be removed by dissolving it with chloroform.