Preparation And Properties Of Chitosan/Functionalized Graphene Oxide Composite Films

With people's attention to environment resources and the improvement of food quality and safety requirements,more and more attention has been paid to the use of natural polymers to make degradable green functional food packaging materials.Chitosan(CS)is a kind of natural polysaccharide biomacromolecule with good biocompatibility,renewability and abundant resources.It has excellent antibacterial and film-forming property,and is one of the ideal biomass materials for food packaging.However,its poor mechanical properties and barrier properties,and its narrow antibacterial spectrum limit its application in the field of food packaging.Therefore,in this study,Rosmarinic Acid(RA)as a natural antibacterial substance was used to functionally modify graphene oxide(GO)which is a derivative of graphene,to synthesize a kind of bifunctional carbon base assistant with excellent reinforcement and antibacterial properties,which was named GO-RA.Then,use chitosan and GO-RA to prepare chitosan-based food packaging materials with high strength,high barrier and high antibacterial properties.The specific research is as follows:(1)GO-RA composites were prepared by functionally modifying GO with natural antibacterial substance RA,and characterized by FTIR,UV-Vis,XRD,TG,SEM and TEM.The results show that RA grafting on GO can further weaken the van der Waals force between the layers and increase the interlayer distance,which was helpful to prevent the agglomeration of GO and increase its dispersion stability;the thermal stability of GO-RA was lower than that of GO;RA grafting on GO did not destroy its basic two-dimensional plane structure,and retains its excellent physical and chemical properties.(2)E.coli and S.aureus were used as model bacteria to study the antibacterial ability of GO-RA.The results showed that with the increase of the concentration,the inhibitory effect of GO-RA and GO on the growth and reproduction of E.coli and S.aureus showed a gradually increasing trend;When GO and GO-RA were at the same concentration,the inhibitory effect of GO-RA on the growth and reproduction of E.coli and S.aureus was stronger than that of GO;GO-RA showed better antibacterial activity to the above two kinds of bacteria than GO,and the bactericidal rates increased by 19.3%and 5.5%respectively.Chitosan/graphene oxide/rosmarinic acid composite films was prepared with chitosan as matrix material and graphene oxide/rosmarinic acid as assistant.The relationship between composite formula and processing conditions on the structure and properties of composite materials was studied.The effects of GO-RA content,chitosan concentration,glycerin content and drying temperature on the thickness,transparency,mechanical properties,the water vapor transmission coefficient,oil permeability coefficient,water solubility and antibacterial activity of composite films were investigated.The results showed that after the modification by RA,graphene oxide was more conducive to dispersion and combination in the chitosan matrix.There was strong hydrogen bond interaction between GO-RA and chitosan molecules,which limits the migration and sliding of chitosan macromolecules,thus improving the thermal stability of chitosan composite membrane;With the increase of GO-RA content,the light transmittance of composite films decreased gradually,both the tensile strength and tensile fracture strain were showed a trend of increasing first and then decreasing,the water vapor transmission coefficient,oil permeability coefficient and water solubility were showed a trend of decreasing first and then increasing;With the increase of chitosan concentration,the thickness of composite films gradually increases,the light transmittance gradually increases,the tensile strength and tensile fracture strain both increased first and then decreased,the water vapor transmission coefficient,oil permeability coefficient and water solubility were showed a trend of decreasing first and then increasing;With the increase of glycerol content,the light transmittance and tensile fracture strain of composite film were showed a trend of increasing first and then decreasing,the tensile strength continuously decrease,both the water vapor transmission coefficient and water solubility were gradually increase,and the oil permeability coefficient decrease first and then increase;With the increase of drying temperature,the tensile strength of the composite films increased first and then decreased,the tensile fracture strain decreased gradually,and the water vapor transmittance decreased first and then increased.When the drying temperature was 45?,the oil permeability coefficient of the composite films reaches the lowest value of0.48mg·mm/(cm~2·d).The best oil-barrier performance was obtained;The bactericidal effect of composite films with different content of GO-RA to E.coli and S.aureus was significantly improved(P<0.05).