European Polymer Journal 172 (2022) 111193 Available online 2 May 2022 0014-3057/© 2022 Elsevier Ltd. All rights reserved. Pectin as a non-toxic crosslinker for durable and water-resistant biopolymer-based membranes with improved mechanical and functional properties Serena Regina a, b , Teresa Poerio a , Rosalinda Mazzei a , Carla Sabia c , Ramona Iseppi c , Lidietta Giorno a, * a National Research Council of Italy, Institute on Membrane Technology (CNR-ITM), Via P. Bucci 17C, 87036 Rende, (CS), Italy b University of Calabria, Department of Physics, Via P. Bucci 33B, 87036 Rende, (CS), Italy c Department of Life Sciences, University of Modena and Reggio Emilia, Via G. Campi 287, 41125 Modena, Italy A R T I C L E INFO Keywords: Pectin Poly(vinyl alcohol) Biopolymer Crosslinked membrane Non-toxic crosslinker Antibacterial-antiradical activity ABSTRACT Biopolymer-based hydrophilic membranes with very high stability in aqueous systems were developed by using pectin as a non-toxic crosslinker. The unique properties of pectin as an effcient crosslinker were demonstrated using poly(vinyl alcohol) as a model for a highly water-soluble biopolymer. The chemical crosslinking strategy using glutaraldhehyde has proven successful in improving the stability of poly(vinyl alcohol) membranes. However, the use of non-toxic biological crosslinking agents has not been fully explored. We hypothesized that pectin, as a biopolymer bearing numerous carboxyl groups, could be a very effcient crosslinker compared to carboxylic acids, promoting unprecedented membrane stability. A systematic characterization of the chemical, thermal, mechanical, and functional properties of membranes prepared from poly(vinyl alcohol) crosslinked with pectin confrmed the excellent stability of the membranes in water, tested at the boiling point and at acidic and basic pH. The use of pectin also resulted in membranes with very high tensile strength, resistance to microbial degradation, antiradical and antibacterial activity, and improved water vapor barrier properties. 1. Introduction The use of biopolymers and green solvents has attracted much attention in recent years for the development of eco-friendly polymer membranes, flms, and hydrogels [1–2]. Poly(vinyl alcohol) (PVA) is a well-known hydrophilic synthetic biopolymer with excellent capabil- ities in flm formation, processability with water, biocompatibility, and availability at low cost [3]. PVA has attracted attention in many felds, such as biomedical applications, food packaging, enzyme immobiliza- tion, membrane technology [1,4–5]. However, in applications requiring durable materials, the use of biopolymer-based membranes is still hin- dered by their instability in aqueous media and their degradation by microbial attack. Indeed, PVA-based membranes and flms still have their limitations due to the high degree of swelling in water, which causes complete dissolution of the materials in aqueous environments, low chemical-physical stability and low durability due to microbial degradation [6]. Various methods have been used to improve the stability of PVA flms in water, such as the use of high molecular weight PVA [7], the formation of ionic bonds with other polymers [8], and more successfully chemical crosslinking [4,6,9–10], which is more effcient to guarantee the formation of water-insoluble materials. Aldehydes (e.g., glutaral- dehyde) have been most commonly used in chemical crosslinking [11–12]. However, aldehydes are toxic compounds and can also cause undesirable modifcations in biopolymers [9]. There are few studies in which non-toxic crosslinking agents such as Abbreviations: CA, citric acid; DL-PLA, Poly-DL-lactic acid; GA, glutaraldehyde; L-PLA, Poly-L-lactic acid; MWCNTs, multiwalled carbon nanotubes; PA6, poly- amide 6; PC, polycarbonate; PCL, Poly-e-caprolactone; PEC, pectin; PEEK, polyetheretherketone; PET, polyethylene terephthalate; PI, polymide; PMMA, poly- methylmethacrylate; PP, polypropelene; PPS, polyphenylene sulphide; PSU, polysulfone; PVA, poly(vinyl alcohol); PVC, polyvinylchloride; PVDF, polyvinylidene fuoride; SA, sulphuric scid; WVP, water vapor permeability. * Corresponding author at: National Research Council of Italy, Institute on Membrane Technology (CNR-ITM), Via P. Bucci 17/C, 87036 Rende, (CS), Italy. E-mail addresses: s.regina@itm.cnr.it (S. Regina), t.poerio@itm.cnr.it (T. Poerio), r.mazzei@itm.cnr.it (R. Mazzei), carla.sabia@unimore.it (C. Sabia), ramona. iseppi@unimore.it (R. Iseppi), l.giorno@itm.cnr.it, Lidietta.giorno@cnr.it (L. Giorno). Contents lists available at ScienceDirect European Polymer Journal journal homepage: www.elsevier.com/locate/europolj https://doi.org/10.1016/j.eurpolymj.2022.111193 Received 13 February 2022; Received in revised form 30 March 2022; Accepted 10 April 2022