Synthesis of poly (4-aminosalicylic acid) through enzymatic and oxidative polycondensation by H2O2 oxidant

Abstract

Aromatic compounds containing hydroxyl and amine groups in their structure are converted into oligomers or polymers through oxidative polymerization in water or organic solvent media. Again, aromatic amine or aromatic hydroxyl compounds are converted into oligomers or polymers by horseradish peroxidase (HRP) enzyme at different pH values in water or organic solvent media. Since the enzymatic oligomerization or polymerization of such compounds is environmentally sensitive, they are referred to as green chemistry. Poly(4-aminosalicylic acid) was synthesized by both enzymatic (PASA-E) and oxidative polycondensation (PASA-O) reactions. The structure and characterization were determined by FTIR, UV–vis, NMR, TGA, fluorescence and SEM measurements.PASA-O from 4-aminosalicylic acid was obtained by chemical oxidative polycondensation in glacial acetic acid by H2O2 (35% aqueous solution) as an oxidant. Enzymatic oxidative polymerizationof 4-aminosalicylic acid was performed by HRP. It has important advantages such as mild reaction conditions, mainly in terms of temperature and toxicity.The optical bandgap (Eg) values of ASA, PASA-O and PASA-E polymers were calculated to be 3.72, 2.40, and 2.73 eV, respectively. The electrochemical properties of compounds were determined by CV. The electrochemical bandgap (E′g) values of PASA-O and PASA-E were determined as 2.16 and 2.68 eV, respectively. The residual amount of PASA-O was higher than that of ASA and PASA-E at 1000 °C.