Preparation Of Polyvinyl Alcohol/Starch And Ag@MOF/Chitosan Derivative Bilayer Antibacterial Composite Films And Their Application In Food Packing

In this study,polyvinyl alcohol/starch film and modified chitosan and its derivatives were used as the base film layers to prepare bilayer films,combining the complementary polyvinyl alcohol/starch film layer and modified chitosan and its derivatives film layer to produce a bilayer film with excellent performance.The antibacterial properties of the films were further improved.In this study,bilayer composite membranes were prepared by flow casting method and the effects of chitosan and its derivatives and silver-based metal organic frameworks at various concentrations on various properties of the composite membranes were investigated.The specific research content of this paper is as follows:1.Preparation of poly(vinyl alcohol)/Ag@MOF monolayer composite films.In order to study the feasibility of the application of silver-based metal organic frameworks in food packaging,Ag@MOF was prepared by hydrothermal synthesis,and the polyvinyl alcohol/Ag@MOF composite films were prepared by flow casting method with polyvinyl alcohol as raw material and Ag@MOF as filler,and the effects of Ag@MOF concentration ratio on the microstructure,barrier ability,mechanical ability,antibacterial properties and cytotoxicity of the composite films were investigated.The results exhibited that Ag@MOF was successfully synthesized.After the addition of Ag@MOF,the mechanical properties of PVA based films are enhanced,and the hydrophobic Ag@MOF was able to influence the movement of water molecules in the films,thus improving the barrier properties of the composite films.However,the cytotoxicity of Ag@MOF has to a certain extent affected the application of its composite films in food packaging.2.Preparation of bilayer antimicrobial composite films of polyvinyl alcohol/maize starch and chitosan derivatives.The lower base layer of the bilayer film was prepared by flow casting using polyvinyl alcohol and corn starch as the main raw materials.Based on the structure of the original polyvinyl alcohol/starch lower layer film,p-coumaric acid-modified chitosan and its nanoparticle solution were used as raw materials to form the bilayer antibacterial composite film material by casting p-coumaric acid-modified chitosan derivative film solution on top of the original polyvinyl alcohol/starch composite film material by the casting method.The microscopic morphology,mechanical strength,antibacterial properties,antioxidant properties and cytotoxicity of the bilayer film were investigated in depth.The experimental results exhibited that the bilayer antibacterial composite film has good microstructure and excellent mechanical properties.Since the lower layer of the bilayer(polyvinyl alcohol/starch)is in direct contact with food and is not cytotoxic,the bilayers are also biocompatible and possess antioxidant and antibacterial properties.The antibacterial properties of the coumaric acid modified chitosan and its nanoparticle bilayers were still lower than those of the PVA/Ag@MOF film.3.Preparation of polyvinyl alcohol/corn starch and p-coumaric acid modified chitosan and its nanoparticles loaded with Ag@MOF bilayer antibacterial composite film.On the basis of the above-mentioned polyvinyl alcohol/starch monolayer composite film construction,a bilayer antibacterial functional composite film material was prepared by casting p-coumaric acid modified chitosan and its nanoparticles as the film-forming material and Ag@MOF as the antibacterial agent,using the flow casting method to prepare a bilayer antibacterial functional composite film material with pcoumaric acid modified chitosan and its nanoparticles loaded with Ag@MOF on the polyvinyl alcohol/maize starch composite film material.The microscopic morphology,mechanical strength,antibacterial activity,antioxidant properties and cytotoxicity of the bilayer films were investigated.The experimental results showed that a synergistic antibacterial effect was formed for coumaric acid-modified chitosan,its nanoparticles and Ag@MOF,and thus the coumaric acid-modified chitosan and its nanoparticles loaded with Ag@MOF had higher antibacterial activity than the single component.The bilayer structure avoids direct contact between the upper layer of antibacterial material and the foodstuff,and maintains the good biocompatibility of the bilayer.Through the above study,a bilayer composite film with high antibacterial performance,antioxidant performance and good biocompatibility was obtained.