Enzymatic Synthesis Of Phenolic Polymers And Research On Their Antioxidant Properties For Polypropylene

Catalyst plays a vital role in the modern chemistry and industrial production. Enzymes, as a biological catalyst, can be used for polymerisation of phenols and anilines. Now, it has aroused many scholars' concerns as a green polymerization method. Horseradish peroxidase(HRP) has already come into the commercial application. Many substances, which are difficult to synthesize by conventional chemical methods, can be synthesized by enzymatic polymerization under mild condition. In this paper, HRP-catalyzed polymerization of phenolic compounds was reported in sodium dodecyl sulfate(SDS) micelle system. Moreover, antioxidant behavior of the as-synthesized polyphenol for tabilization of polypropylene(PP) was investigated.1. Polyguaiacol, a purple powder, was synthesized by HRP in SDS micellar system. Fourier Transform Infrared Spectroscopy(FTIR), gel permeation chromatography(GPC), and thermal gravimetric analysis(TGA) were used to characterize the structure and the thermal property of the as-synthesized polyguaiacol. Results showed the number average molecular weight of polyguaiacol is 5.9 × 102, and it has better thermal stability than tne monomer. Next, the as-synthesized polymer was added into PP powder as antioxidative additive. The oxidation induction times(OITs) of PP compounds were used to compare the antioxidant efficiency of polyguaiacol and commercially available antioxidants. TGA dates were used to conduct the thermal decomposition kinetics study of PP compounds. Besides, the accelerated aging test was carried out to investigate the changes of chemical composition and tensile property of PP compounds in aging. The results showed that the as-perpared polyguaiaol can be used as a new bioinspired antioxidant for the stabilization of polypropylene.2. Poly(p-tert-butyl catechol), a russet powder, was synthesized by HRP in SDS micellar system. Nuclear magnetic resonance spectroscopy(H1 NMR) was used to determine the aggregate position in the palisade layer of the aqueous micelle. Results showed that the aggregation of p-tert-butyl catechol is mainly dominant between C2 and C6 of its aliphatic chain. The structure and properties of the as-synthesized polymer were characterized by FTIR, GPC and Maldi-Tof-MS. Result of GPC showed the number average molecular weight of the as-synthsized poly(p-tert-butyl catechol) is 5.4 × 102. And result of Maldi-Tof-MS showed that poly(p-tert-butyl catechol) mostly is trimers, tetramers. Result of TGA showed that the thermal property of polymer is much better than the corresponding monomer. After melt blending and extrusion of the as-synthesized polymer and PP powder, the oxidation induction time(OIT) and oxidation induction temperature(OOT) of PP/poly(p-tert-butyl catechol) were determined by DSC. Result showed that antioxidant efficiency of poly(p-tert-butyl catechol) is superior to the corresponding monomer and commercially antioxidant 1076. TGA dates were used to analysis the thermal oxidation degradation process of PP compounds. The results showed that addition of poly(p-tert-butyl catechol) can improved the apparent activate energy of the thermal oxidation degradation of PP. Thus, enzymatic polymerization of phenolic compounds provides a green and efficient synthetic method of antioxidants.