Kinetic study, characterization and theoretical studies of oxidative chemical polymerization of para-aminophenol in acid medium using k2cr2o7 as oxidizing agent
Author(s): Sayyah S. M.*, Moustafa H., El-Ghandour A. H., Aboud A. A., Ali M. Y.
Abstract
The synthesis of poly-p-aminophenol (PPAP) by oxidative chemical polymerization using potassium dichromate as oxidizing agent was carried out. The optimum conditions for the polymerization reaction were investigated. The order of reactions and thermodynamic activation parameters were calculated. A molecular mechanism for the oxidation of p-aminophenol using potassium dichromate is proposed. This mechanism explains the specific features of p-aminophenol oligomerization and polymerization reactions. Spectroscopic studies using IR, UV–vis and elemental analysis have evidenced the structure of polymeric chain. The surface morphology of the obtained polymer was characterized by X-ray diffraction and transmission electron microscopy (TEM). The thermo gravimetric analysis (TGA) was used to confirm the proposed structure and number of water molecules in each polymeric chain unit. Moreover, determinations of dielectric properties of the prepared polymer at the investigated optimum condition were carried out. The a.c conductivity (σac) of (PPAP) was investigated as a function of frequency and temperature. The microscopic conduction mechanism of charge carries over the potential barrier in polymer backbone was found to be classical hopping model. The equilibrium ground state geometric parametric of p-aminophenol (PAP) neutral monomer and radical cation are investigated theoretically using DFT – B3LYP/ 6-311G** level of calculation. The initiation and propagation steps of oxidative chemical polymerization are theoretically investigated.
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