Lim, J. Y.; Krishnan, R.; Seayad, J.; Sana, B.; Ghadessy, F. J.; Jana, S.; Ramalingam, B., Laccase-catalyzed synthesis of low-molecular-weight lignin-like oligomers and their application as UV blocking materials. Chemistry – An Asian Journal 2018, 13 (3), 284-291.
The laccase‐catalyzed oxidative polymerization of monomeric and dimeric lignin model compounds was carried out with oxygen as the oxidant in aqueous medium. The oligomers were characterized by using gel permeation chromatography (GPC) and matrix‐assisted laser desorption ionization time‐of‐flight mass spectroscopy (MALDI‐TOF MS) analysis. Oxidative polymerization led to the formation of oligomeric species with a number‐average molecular weight (Mn) that ranged from 700 to 2300 Da with a low polydispersity index. Spectroscopic analysis provided insight into the possible modes of linkages present in the oligomers, and the oligomerization is likely to proceed through the formation of C−C linkages between phenolic aromatic rings. The oligomers were found to show good UV light absorption characteristics with high molar extinction coefficient (5000–38 000 m−1 cm−1) in the UV spectral region. The oligomers were blended independently with polyvinyl chloride (PVC) by using solution blending to evaluate the compatibility and UV protection ability of the oligomers. The UV/Vis transmittance spectra of the oligomer‐embedded PVC films indicated that these lignin‐like oligomers possessed a notable ability to block UV light. In particular, oligomers obtained from vanillyl alcohol and the dimeric lignin model were found to show good photostability in accelerated UV weathering experiments. The UV‐blocking characteristics and photostability were finally compared with the commercial low‐molecular‐weight UV stabilizer 2,4‐dihydroxybenzophenone.
This work was funded by the Agency for Science, Technology, and Research (A*STAR), Singapore, under the “No Small Organic Compounds” (NoSOC) program for environmentally friendly specialty products.
This is the peer reviewed version of the following article: Lim, J. Y.; Krishnan, R.; Seayad, J.; Sana, B.; Ghadessy, F. J.; Jana, S.; Ramalingam, B., Laccase-catalyzed synthesis of low-molecular-weight lignin-like oligomers and their application as UV blocking materials. Chemistry – An Asian Journal 2018, 13 (3), 284-291, which has been published in final form at https://doi.org/10.1002/asia.201701573. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions.