Enzyme Catalyzed Polymerization Of Aromatic Amines And Phenolic Derivatives In Dioxane

Phenylenediamines, aminophenols, methoxyanil ines, and 1,4- hydroquinone, 1-naphthylamine were polymerized via the catalysis of horseradish peroxidase (HRP) in mixed solvents of l,4-dioxane and water at amibient conditions by using hydrogen peroxide as the oxidant. Several factors influencing the polymer yield, such as the concentration of the substrate, pH value and oxidant amount were examined using a- phenylenediamine as substrate. The polymerization mechanism of bifunctional monomer has originally been discussed, and the structure and properties of the obtained polymers were characterized. Some conclusions were obtained as follows: 1. Using o-phenylenediamine as substrate, several polymerization conditions were examined. As the concentration of the substrate in dioxane increases, the polymer yield increases quite obviously although it is still not so high, while the molecular weight remains almost unchanged; as the pH value varied in the range of 6.0 to 7.0, the variation of the yields is not obvious; when increasing the amount of the oxidant, hydrogen peroxide, the polymer yield increases rapidly, but the molecular weight only slightly increased. 2. The structure of the obtained polymers was characterized by using nuclear magnetic resonance, infrared technique, ultraviolet-visible spectrum. Molecular weight of the polymers was determined by gel permeation chromatography. In case of bifunctional monomers, the polymers formed were found to be constructed mainly in a linear form but mixed repeat units, which is derived from multiple active points on the benzene ring. 3. Thermal and electrochemical properties of the obtained polymers have been examined and acquired some useful data. At least four polymers were found to have electrical active property. Poly(4- aminophenol) shows a good reversible electro-activity, having an oxidation potential of 0.45V and a reduction potential of 0.40V with respect to a saturated HgCI2 electrode; poly(p-phenylenediamine) displays an oxidation potential of 0.78V, which does not appear to be completely reversible. As a result, the doped poly(p- phenylenediamine) shows a initial conductivity in the semiconducting region (103S cm-?, but decays with time under unchanged voltage. 4. Compared with the polyaniline derived from chemical and electrochemical methods, the enlargement of the conjugated structure is difficult due to the complicated chain construction of the polymers synthesized via the enzyme approach, leading to a total different property. 5. The polymerization mechanism was also discussed on the basis of the above results, including the activity and the selectivity of the enzyme.