An Antioxidant Bioinspired Phenolic Polymer for Eﬃcient Stabilization of Polyethylene Veronica Ambrogi, †,¶ Lucia Panzella, ‡,¶ Paola Persico, § Pierfrancesco Cerruti,* ,§ Carlo A. Lonz, † Cosimo Carfagna, § Luisella Verotta, ∥ Enrico Caneva, ⊥ Alessandra Napolitano, ‡ and Marco d’Ischia* ,‡ † Department of Materials and Production Engineering, University of Naples “Federico II”, P.le Tecchio 80, 80125 Napoli, Italy ‡ Department of Chemical Sciences, University of Naples “Federico II”, Via Cintia 4, 80126, Naples, Italy § Institute of Polymer Chemistry and Technology (ICTP-CNR), via Campi Flegrei 34, 80078 Pozzuoli (Na), Italy ∥ Department of Chemistry, University of Milan, via C. Golgi 19, 20133 Milano, Italy ⊥ Interdepartmental Center for Large Instrumentation (CIGA), via C. Golgi, 19, 20133 Milano * S Supporting Information ABSTRACT: The synthesis, structural characterization and properties of a new bioinspired phenolic polymer (polyCAME) produced by oxidative polymer- ization of caﬀeic acid methyl ester (CAME) with horseradish peroxidase (HRP)-H 2 O 2 is reported as a new sustainable stabilizer toward polyethylene (PE) thermal and photo-oxidative degradation. PolyCAME exhibits 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 chemilumines- cence, and FTIR spectroscopy and mechanical tests indicate a signiﬁcant eﬀect of polyCAME on PE durability. Data from antioxidant capacity tests suggest that the protective eﬀects of polyCAME are due to the potent scavenging activity on aggressive OH radicals, the eﬃcient H-atom donor properties inducing free radical quenching, and the ferric ion reducing ability. PolyCAME is thus proposed as a novel easily accessible, eco-friendly, and biocompatible biomaterial for a sustainable approach to the stabilization of PE ﬁlms in packaging and other applications. ■ INTRODUCTION In the last few years, there has been an increasing demand on the part of consumers and the market for natural or renewable resource materials that could be used in the place of synthetic counterparts as building blocks for thermoplastic and thermosetting resins. 1−3 Several examples including the polymerization of natural monomers and their derivatives to obtain thermoplastic polymers with properties similar to those of commodity thermoplastics have been reported. 4−6 Fur- thermore, health and environmental concerns posed by the use of several chemicals involved in the synthesis of thermosets underscored the need for the development of a sustainable supply of biobased resins. 7−9 Interestingly, biobased phenolic functional polymers have been also described, acting as ﬂame retardants or antioxidants when added in polymer matri- ces. 10−13 It is known that hindered phenolics are widely used as primary antioxidants for polymers employed in food pack- aging. 14−16 As a matter of fact, oxidative deterioration of packaged food may cause signiﬁcant decreases in shelf life associated with oﬀ-ﬂavors, oﬀ-odors, color changes, and nutritional loss and is therefore emerging as a major economic and health issue, especially with the ever increasing demand for long life foods. Although antioxidant additives, such as butylated hydroxyanisole, butylated hydroxytoluene, tert- butylhydroquinone, and propyl gallate, have been added into food product formulations to inhibit oxidative reactions, issues regarding possible toxic, mutagenic, and carcinogenic eﬀects of these additives have been raised, as previous observations indicated that small phenolic antioxidants may be released from polymer packaging ﬁlms when in contact with water or beverages. 17 Therefore, low and medium molecular weight natural phenolics, such as caﬀeic acid, natural rosemary extracts, ascorbic acid, α-tocopherol, curcumin, quercetin, and catechins, have been incorporated into diﬀerent packaging materials and their stabilizing eﬀects have been investigated. 18−26 Little attention has been placed so far to the use of polymers of natural phenolics as bioavailable, biocompatible antioxidants for polymer stabilization 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, and so forth). Received: October 18, 2013 Revised: November 26, 2013 Article pubs.acs.org/Biomac © XXXX American Chemical Society A dx.doi.org/10.1021/bm4015478 | Biomacromolecules XXXX, XXX, XXX−XXX