BackgroundPeroxidases are emerging as an important class of enzymes that can be used for the efficient degradation of organic pollutants. However, detailed studies identifying the various intermediates produced and the mechanisms involved in the enzyme-mediated pollutant degradation are not widely published.ResultsIn the present study, the enzymatic degradation of an azo dye (Crystal Ponceau 6R, CP6R) was studied using commercially available soybean peroxidase (SBP) enzyme. Several operational parameters affecting the enzymatic degradation of dye were evaluated and optimized, such as initial dye concentration, H2O2 dosage, mediator amount and pH of the solution. Under optimized conditions, 40 ppm dye solution could be completely degraded in under one minute by SBP in the presence of H2O2 and a redox mediator. Dye degradation was also confirmed using HPLC and TOC analyses, which showed that most of the dye was being mineralized to CO2 in the process.ConclusionsDetailed analysis of metabolites, based on LC/MS results, showed that the enzyme-based degradation of the CP6R dye proceeded in two different reaction pathways- via symmetric azo bond cleavage as well as asymmetric azo bond breakage in the dye molecule. In addition, various critical transformative and oxidative steps such as deamination, desulfonation, keto-oxidation are explained on an electronic level. Furthermore, LC/MS/MS analyses confirmed that the end products in both pathways were small chain aliphatic carboxylic acids.

Our interest in the fabrication of high‐performance polyimides has led to thiourea‐substituted poly(thiourea‐ether‐imide)s (PTEIs) with good retention of thermal properties along with flame retardancy. A new aromatic monomer, 4,4′‐oxydiphenyl‐bis(thiourea) (ODPBT), was efficiently synthesized and polymerized with various dianhydrides (pyromellitic dianhydride, 3,3′,4,4′‐benzophenonetetracarboxylic dianhydride and 4,4′‐(hexafluoroisopropylidene)diphthalic dianhydride) via two‐stage chemical imidization to fabricate a series of PTEIs. The structural characterization of ODPBT and the polymers was carried out using Fourier transform infrared, 1H NMR and 13C NMR spectral techniques along with crystallinity, organosolubility, inherent viscosity and gel permeation chromatographic measurements. PTEIs bearing CS and Omoieties in the backbone demonstrated an amorphous nature and were readily soluble in various amide solvents. The novel polymers had inherent viscosities of 1.16–1.23 dL g−1 and molecular weights of ca 90 783–96 927 g mol−1. Their thermal stability was substantiated via 10% weight loss in the temperature range 516–530 °C under inert atmosphere. The polyimides had glass transition temperatures of 260–265 °C. Incorporation of thiourea functionalities into polymer backbones is demonstrated to be an effective way to enhance their thermal properties and flame retardancy. Thus, ODPBT can be considered as an excellent candidate for use in the synthesis of high‐performance polymeric materials. Copyright © 2010 Society of Chemical Industry

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The present work accounts for the influence of aromatic amide oligomers on the inherent brittleness of cured epoxy. Aromatic and aliphatic amine‐terminated amide oligomers have been prepared by condensation polymerization using isophthaloyl dichloride and two different amines. The oligomers have been characterized using Fourier transform infrared spectroscopy and wide angle X‐ray diffraction analysis. Diglycidyl ether of bisphenol A (DGEBA) is cured with a diamine (4,4′‐oxydianiline) by using different weight ratio of oligomers. The FTIR of cured epoxy shows ring opening by the disappearance of oxirane ring peak at 913 cm−1, whereas X‐ray diffraction shows its amorphous phase in the cured state. The thermogravimetric analysis of the resultant composites shows that the thermal stability slightly decreases (467–454 °C) with increasing the oligomer content from 5 to 25 wt %, whereas the mechanical parameters (Young's modulus, tensile strength, impact strength, and elongation at break) increase with increase in the oligomer content. DMA shows lower tanδ values for aliphatic amine‐terminated oligomers for cured epoxy. Two‐phase surface morphology is observed through scanning electron microscopy. Owing to their high mechanical and thermal properties, aromatic amides have observed to greatly influence the mechanical properties of cured epoxy, particularly its brittleness. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48404.

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