Novel antioxidant bioinspired phenolic polymers and their applications in packaging

Polymers of natural polyphenols have so far received little attention as bioavailable, biocompatible antioxidants for different applications e.g. in packaging and related technologies. Expected advantages with respect to the monomers would include lower volatility (with reduced adverse effects), greater chemical stability under processing conditions and lower tendency to be released from the polymer into the contact medium (food, water, etc.). Herein we report data on the synthesis, structural characterization and antioxidant properties of two novel bioinspired phenolic polymers prepared by horseradish/H2O2 oxidation of tyrosol (polyTYR) and caffeic acid methyl ester (polyCAME). The materials, obtained in 80-85% yields, were subjected to structural characterization by solid state CPMAS NMR, mass spectrometry and gel permeation chromatography (GPC). ESI(-)/MS and NMR analysis indicated that polyTYR was a mixture of regular oligomers up to the undecamer with heptamer as the most abundant, all featuring units linked through C-C bonds. GPC showed an average molecular weight of 1862 Da with a polydispersity index of 1.64. ESI(-)/MS of polyCAME showed oligomers up to at least the decamer stage, peaking at the tetramer. Analysis of the clusters of the pseudomolecular ion peaks and the presence of CH carbons due to O-substituted benzylic positions in NMR spectra suggested a structure including dihydrobenzofuran units. Both PolyTYR and polyCAME exhibited antioxidant properties in the 2,2-diphenyl-1-picrylhydrazyl (DPPH) and ferric reducing/antioxidant power (FRAP) assays and proved to be efficient hydroxyl radical scavengers in a Fenton reaction assay. The potential of PolyCAME as stabilizer toward polyethylene (PE) thermal and photo-oxidative degradation was also evaluated. PolyCAME exhibited high stability toward decarboxylation and oxidative degradation during the thermal processes associated with PE film preparation. Characterization of PE films by thermal methods, photo-oxidative treatments combined with chemiluminescence and FTIR spectroscopy and mechanical tests indicated a significant effect of polyCAME on PE durability as shown for example by the increase of the Oxidative Induction Time (OIT).1The synthesized phenolic biopolymers are thus proposed as novel easily accessible, eco-friendly and biocompatible materials for a sustainable approach in packaging and other applications. 1) Ambrogi, V.; Panzella, L.; Persico, P.; Cerruti, P.; Lonz, C. A.; Carfagna, C.; Verotta, L.; Caneva, E.; Napolitano, A.; d'Ischia, M. Biomacromolecules 2014, 15, 302-310.