Synthesis, characterization and antimicrobial properties of 4-[(4-hydroxybenzylidene) amino] phenol and its polymer

The oxidative polycondensation reaction conditions of 4-[(4- hydroxybenzylidene) amino] phenol (4- HBAP) were studied with H2O2, air oxygen and NaOCl in an aqueous alkaline medium between 50 and 90 C. The structures of the obtained monomer and polymer were confirmed by FT-IR, UV-Vis, H-1- and C-13-NMR and elemental analysis. The characterization was made by TG-DTA, size exclusion chromatography (SEC) and solubility tests. At the optimum reaction conditions, the yield of poly[ 4-(4- hydroxybenzylidene amino) phenol] (P-4-HBAP) was found to be 48.3% (for H2O2 oxidant), 80.5% (for air O-2 oxidant) and 86.4% ( for NaOCl oxidant). According to the SEC analysis, the number-average molecular weight (Mn), weight-average molecular weight (Mw) and polydispersity index (PDI) values of P-4-HBAP was found to be 8950, 10970 g mol(-1) and 1.225, respectively, using H2O2; and 11610, 15190 g mol(-1) and 1.308 respectively, using air O-2 and 7900, 9610 g mol(-1) and 1.216, respectively, using NaOCl. According to TG-DTA analyses, P-4-HBAP was more stable than 4- HBAP against thermal decomposition. The weight loss of P-4-HBAP was found to be 49.27% at 1000 C. The highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) values calculated from electrochemical measurement. Electrochemical energy gaps (Eg ') of 4- HBAP and P-4-HBAP were found to be -5.46, -5.28; -2.26, -2.67; 3.20 and 2.61 eV, respectively. According to UV-Vis measurements, optical band gap (Eg) of 4- HBAP and P-4-HBAP were found to be 3.34 and 3.01 eV, respectively. Also, antimicrobial activities of 4- HBAP and P-4-HBAP were examined against selected some bacteria. The electrical conductivity of the polymer was measured after doping with iodine.