Synthesizing Hindered Structure Poly (p‐Phenylenediamine) by Enzymatic Catalysis and Evaluating Its Antioxidation Mechanism in Biodegradable Castor Oils

Abstract

In this study, poly(p‐phenylenediamine) (PPDA) was synthesized by an enzymatic polymerization method using p‐phenylenediamine as the monomer in the water phase. The PPDA structure was characterized by infrared (IR), gel permeation chromatography, and elemental analysis. The antioxidation behavior of the as‐synthesized PPDA in biodegradable castor oil was investigated using a rotary oxygen bomb test and pressurized differential scanning calorimetry. A theoretical calculation was conducted to investigate its antioxidation mechanism. PPDA was found to exhibit excellent oxidation resistance in castor oil at 150 °C, which effectively prolonged the oxidation induction time of the oil. The results obtained herein suggest that as with phenolic antioxidants, PPDA with a hindered structure effectively improves the antioxidation performance of the oil by enhancing the stability of nitrogen free radicals.

Controllable Synthesis and Synergistic Antioxidation Mechanism of Poly(p-methoxyphenol-phenylamine) in Biodegradable Vegetable-Based Lubricating Oils

“…Poly­( p -methoxyphenol-phenylamine) (P­(MOP-PA)) was synthesized by liquid-phase copolymerization of p -methoxyphenol and aniline, which was detailed in our previous publication . Poly­( p -phenylenediamine), denoted as PPDA, was prepared with p -phenylenediamine as the monomer and used for a comparative study . The synthetic routes are schematically illustrated in Figure .…”

“…27 Poly(p-phenylenediamine), denoted as PPDA, was prepared with p-phenylenediamine as the monomer and used for a comparative study. 28 The synthetic routes are schematically illustrated in Figure 1.…”