Oxidative polymerization of 4-[(4-phenylazo-phenyimino)-methyl]-phenol catalyzed by horseradish peroxidase

Schiff base derivate 4-[(4-phenylazo-phenyimino)-methyl]-phenol (4-PPMP) monomer was synthesized by condensation reaction and the chemical structure of the monomer has been characterized by UV–vis, FT-IR, 1H NMR spectroscopies. 4-PPMP readily dissolves in 1,4-dioxane, THF, DMF, diethyl ether, chloroform and DMSO. Its solubility in methanol and ethanol is much lower. Enzymatic oxidative polymerization of azobenzene derivate 4-[(4-phenylazo-phenyimino)-methyl]-phenol using horseradish peroxidase (HRP) in the presence of hydrogen peroxide as catalyst and oxidizing agent was carried out in various solvents (acetone, methanol, ethanol, N,N-DMF, and 1,4-dioxane) and phosphate buffers (pH 6, 6.8, 7, and 7.2) at room temperature. Studies have shown that a black polymer having a melting point of 290 °C was successfully produced in good yields by utilizing aqueous 1,4-dioxane as the solvent at pH 6. Poly(4-[(4-phenylazo-phenyimino)-methyl]-phenol) P(4-PPMP) shows good solubility in 1,4-dioxane, DMF and DMSO but it is only sparingly soluble in chloroform, THF, methanol and ethanol. P-(4-PPMP) is insoluble in diethyl ether. Characterization of P-(4-PPMP) was carried out via UV–vis, FT-IR, 1H NMR, elemental analysis and SEC measurements. The number-average molecular weight (Mn), weight-average molecular weight (Mw) and polydispersity index (PDI) of the polymer were determined to be 7970.4, 8146.2 and 1.02 g mol−1, respectively. FT-IR and 1H NMR studies confirmed the presence of phenylene and oxyphenylene units with in the polymer backbone. The optical band gaps (Eg) of 4-PPMP and P-(4-PPMP) were calculated as 3.69 and 3.36 eV, respectively.