title: Borate cross-linked graphene oxide-chitosan as robust and high gas barrier films.
abstract: Chitosan (CS) is one of the most promising polymers due to its biocompatibility, biodegradability, and natural abundance. However, its poor mechanical and barrier properties make it difficult to satisfy a wide range of applications. Herein, borate ions, originating from the hydrolysis of sodium tetraborate decahydrate (borax), have been used to crosslink chitosan and graphene oxide (GO) nanocomposites. Chitosan films consisting of 1.0 wt% boron and 1.0 wt% GO exhibit a significant improvement in both the toughness and oxygen barrier properties compared to pristine chitosan. In particular the tensile strength of the samples after thermal treatment increases by ∼160% compared to pristine chitosan, whereas their oxygen permeability reduces by ∼90%. This is ascribed to the chemical crosslinking between chitosan and GO nanoplatelets through borate ions, as well as the formation of a layered morphology with graphene nanoplatelets oriented parallel to the sample surface. The exceptional robust and high gas barrier film has promising application in the packaging industry. The borate-crosslinking chemistry represents the potential strategy for improving properties of other polymer nanocomposites.
authors.affiliation: Institute of Polymers, Composites and Biomaterials, National Research Council, P.le Fermi, 1-80055 Portici, NA, Italy. gbuonoco@unina.it and Xi'an Modern Chemistry Research Institute, Xi'an 710065, China.
authors.forename: Ning
authors.initials: N
authors.lastname: Yan
authors.affiliation: Institute of Polymers, Composites and Biomaterials, National Research Council, P.le Fermi, 1-80055 Portici, NA, Italy. gbuonoco@unina.it.
authors.forename: Filomena
authors.initials: F
authors.lastname: Capezzuto
authors.affiliation: Institute of Polymers, Composites and Biomaterials, National Research Council, P.le Fermi, 1-80055 Portici, NA, Italy. gbuonoco@unina.it.
authors.forename: Marino
authors.initials: M
authors.lastname: Lavorgna
authors.affiliation: Institute of Polymers, Composites and Biomaterials, National Research Council, P.le Fermi, 1-80055 Portici, NA, Italy. gbuonoco@unina.it.
authors.forename: Giovanna G
authors.initials: GG
authors.lastname: Buonocore
authors.affiliation: Institute of Polymers, Composites and Biomaterials, National Research Council, P.le Fermi, 1-80055 Portici, NA, Italy. gbuonoco@unina.it.
authors.forename: Fabiana
authors.initials: F
authors.lastname: Tescione
authors.affiliation: State Key Laboratory of Polymer Materials Engineering, Polymer Research Institute of Sichuan University, Chengdu 610065, China. xiahs@scu.edu.cn.
authors.forename: Hesheng
authors.initials: H
authors.lastname: Xia
authors.affiliation: Institute of Polymers, Composites and Biomaterials, National Research Council, P.le Fermi, 1-80055 Portici, NA, Italy. gbuonoco@unina.it.
authors.forename: Luigi
authors.initials: L
authors.lastname: Ambrosio