Enzymatic polymerization of aniline and phenol derivatives catalyzed by horseradish peroxidase in dioxane(II)

Aminophenols, methoxyanilines and 1‐naphthylamine were polymerized via the catalysis of horseradish peroxidase in dioxane at ambient conditions by using hydrogen peroxide as the oxidant. Polymers formed in good yields when using double the amount of the oxidant. The molecular weight of the polymers was determined by gel permeation chromatography, and the polymer structures were characterized by using nuclear magnetic resonance and infrared techniques. The polymerization of aminophenols and 1‐naphthylamine gave relatively high yields, while the polymer yields of methoxyanilines were very low. Except for 4‐methoxyaniline giving 23.5% yield, 2‐ and 3‐methoxyaniline gave < 20% and < 10% yield respectively. The polymer of 2‐aminophenol was characterized as a linear, phenoxazine‐like structure, while poly(4‐aminophenol) has a linear, meta‐oriented structure with the preservation of a hydroxyl group. Both of these are very different to those formed by chemical or electrochemical methods. Poly(3‐aminophenol) and poly(1‐naphthylamine) formed by enzymatic polymerization have very complicated structures. UV‐vis spectra and the cyclic voltammograms of the polymers produced were also examined. It has been proved that poly(2‐aminophenol) and poly(4‐aminophenol) have electroactivity with respect to a saturated HgCl2 electrode in 1 M HCl.