DC Electrical Conductivity of Some Oligoazomethines Doped with Nanotubes

Abstract

Three aromatic oligoazomethines containing seven benzene rings each were synthesized. The terminal rings were substituted with different organic groups; namely, OH, H, and NO2. Synthesis was carried out according to the literature by condensing the para-substituted benzaldehydes with benzidine to give the three rings compound, which is then condensed with terephthaldehyde to give the respective seven benzene rings oligomer. The oligomers were used to investigate the effects of molecular structure on the electronic structure, as well as electronic and electrical properties. DC electrical conductivity variation of oligoazomethines is studied in the temperature range 300–500 K after annealing for 24 h at 100°C and after doping with 25 and 50 wt% Multi Wall Nanotubes (MWNTs). An attempt is made to relate DC electrical conductivity and electronic properties to chain length, substituted groups and coplanarity. The different groups attached to the ends showed a small effect on conductivity of the different oligomers in the following order: electron donating > neutral > electron withdrawing groups. Oligoazomethines-MWNTs gave a value of (10−4 Scm−1) as the highest electrical conductivity at higher temperatures. DC electrical conductivity was interpreted using the band energy model. The narrow-gap activation energies noted suggest its application in formulation of photovoltaic panels.