Kinetic studies of the aqueous oxidative polymerization of 3-hydroxyaniline and characterization of the polymer obtained

Abstract

The aqueous polymerization of 3-hydroxyaniline (3HA) was studied using sodium dichromate as oxidant in presence of hydrochloric acid. The effect of hydrochloric acid, sodium dichromate and monomer concentration on the polymerization rate, specific viscosity of the obtained polymer and a.c.conductivity was investigated. The initial and overall reaction rates increase with the increase in hydrochloric acid concentration or sodium dichromate concentration but decrease with the increase in the monomer concentration. The specific viscosity values increase with increasing of hydrochloric acid concentration or monomer concentration which means that the molecular weight of the polymer samples increases in the same direction. But the molecular weight decreases with increasing sodium dichromate concentration. The highest a.c. conductivity value of the obtained polymer was found in case of using 0.0019 g mol/L of Na 2 Cr 2 O 7 , 0.1 M HCl and 0.1 M monomer solution in the reaction medium. Some electrical properties of this sample were investigated as a function of temperature. The order of the polymerization reaction with respect to hydrochloric acid, Na 2 Cr 2 O 7 and monomer concentration was found to be 1.13, 1.2 and m 0.909 respectively. The apparent activation energy (E a ) for this polymerization system was found to be 6.1248 2 10 4 J/mol. The obtained poly(3-hydroxyaniline) was characterized by UV-visible, IR spectroscopy, X-ray diffraction analysis and electron microscopy studies. The thermogravimetric analysis (TGA) and differential thermal analysis (DTA) results were used to confirm the structure.