SYNTHESIS, CHARACTERIZATION, THERMAL DEGRADATION AND ELECTROCHEMICAL PROPERTIES OF OLIGO-4-m-TOLYLAZOMETHINEPHENOL

The oxidative polycondensation reaction conditions of 4-m-tolylazomethinephenol (4-TAMP) in the presence of air O2 and NaOCl as oxidants were studied in an aqueous alkaline medium between 50 and 90°C. The structures of the obtained monomer and oligomer were confirmed by FT-IR, UV-Vis, 1H- and 13C-NMR and elemental analysis techniques. The physical characterization was made by TG-DTA, size exclusion chromatography (SEC) and solubility tests. At the optimum reaction conditions, the yield of oligo-4-m-tolylazomethinephenol (O-4-TAMP) was found to be 62.50% (for air O2 oxidant) and 90.0% (for NaOCl oxidant), respectively. According to the SEC analysis, the number-average molecular weight (Mn), weight-average molecular weight (Mw) and polydispersity index (PDI) values of O-4-TAMP were found to be 2310, 2610 g mol-1 and 1.13, respectively, using air O2, and 1390, 1710 g mol-1 and 1.23, using NaOCl, respectively. According to TG-DTA analyses, O-4-TAMP was more stable than 4-TAMP against thermal decomposition. The weight losses of 4-TAMP and O-4-TAMP were found to be 68% and 58% at 1000°C. Electrical conductivity of the O-4-TAMP was measured, showing that the polymer is a typical semiconductor. Electrochemically, the highest occupied molecular orbital (HOMO), the lowest unoccupied molecular orbital (LUMO) and electrochemical energy gaps (E′g) for 4-TAMP are -5.96, -3.22 and 2.74 eV, respectively. The HOMO, LUMO and (E′g) for O-4-TAMP are -5.78, -3.44 and 2.34 eV, respectively. According to UV-Vis measurements, optical band gaps (Eg) of 4-TAMP and O-4-TAMP were found to be 3.45 and 3.10 eV, respectively.