Enzymatic oxidative polymerization of para -imine functionalized phenol catalyzed by horseradish peroxidase

Enzyme-catalyzed synthesis of 4-methylcatechol oligomer and preliminary evaluations as stabilizing agent in polypropylene

In the present work, 4-methylcatechol oligomer has been prepared by using enzyme-catalyzed polymerization in water and preliminary evaluations as stabilizing agent in polypropylene (PP) was performed. In comparison with intrinsic PP, the oxidation onset temperature of the 4-methylcatechol oligomer/PP composite increased by 66°C, and the oxidation induction time increased by 40 min. In addition, the mixing of a 4-methylcatechol oligomer with PP (i.e., in the formation of a 4-methylcatechol oligomer/PP composite) did significantly enhance the long-term stability of PP in a thermal oxidative environment. Moreover, the tensile strength of this composite did not significantly decrease after aging for 800 h in an air atmosphere at 120°C. These results show that the addition of a 4-methylcatechol oligomer will markedly delay the aging and degradation of PP materials, even under extreme conditions. Thus, an enzyme-catalyzed polymerization of phenol compounds may provide a new avenue toward the preparation of novel antioxidants.

Synthesis and antioxidant activities of phenolic Schiff base monomers and polymers

In this work, synthesis, characterization, and antioxidant activities of two Schiff base monomers (1 and 2) and their corresponding oxidation products (3 and 4) were reported. The monomers were prepared by condensation of 8-amino-2-naphthol with 2,4-dihydroxybenzaldehyde and 3,4-dihydroxybenzaldehyde, and then, they were oxidized to in alkaline medium by NaOCl to obtain the corresponding oxidation products. The compounds 1–4 were characterized by various spectral techniques. The analysis results indicated that the oxidation products had a chain structure consisting of randomly ordered phenylene and oxyphenylene units. In vitro antioxidant activities of 1–4 were evaluated against a ABTS cation radical and a DPPH free radical and compared with standard natural antioxidants, vitamin C (ascorbic acid), and vitamin E (α-tocopherol). The ferric reducing antioxidant power and ferrous-ion chelating activities of 1–4 were also determined.