Preparation And Performance Enhancement Of High Oxygen Barrier Nanocomposites Based On Hydrogen-bonding Interaction

Biodegradable polymers can effectively solve the problems of white pollution and resource shortage caused by traditional polymers,but their poor gas barrier properties limit their popularization.Graphene oxide is an ideal filler to enhance the barrier properties of polymers due to its gas impermeability,ultra-high aspect ratio,and easy functionalization.In this paper,graphene oxide was covalently grafted and modified by polar molecular chains to obtain modified graphene oxide(MGO).Then the high oxygen barrier MGO/polyvinyl alcohol nanocomposites were prepared and characterized to investigate the effect of the grafted chains'length or structure on microstructure and oxygen barrier properties of nanocomposites in details.On this basis,molecular simulation technology was used to construct nanocomposite interface models,and reveal the regulation mechanism of graphene oxide surface characteristics on interface interaction,interface micro-structure and interface barrier properties.Then combining the results of molecular simulation with the macroscopic analysis model,a gas permeation model that reflects the characteristics of the interface layer was constructed to explore the relationship between the surface characteristics of graphene oxide and the macroscopic gas barrier properties of nanocomposite.The main contents are as follows:(1)Diethylenetri amine(DETA),triethylenetri amine(TETA),tetraethylenetri amine(TEPA),?-hydroxy-?-amino polyethylene glycol(NH₂PEG)and 4,4'-Oxydianiline(ODA)were used to modify GO to prepare modified graphene oxide(MGO)with different surface properties.FT-IR,Raman and EDS indicate that the polar molecular chains were successfully grafted onto the GO surface.XRD and SEM show that the grafted polar molecular chains enlarged the layer spacing and increased the surface roughness of GO.(2)MGO/PVA nanocomposites(DETA-GO/PVA,TETA-GO/PVA,TEPA-GO/PVA,NH₂PEG-GO/PVA and ODA-GO/PVA)were prepared by the solution-casting method.FT-IR,XRD,SEM and DSC show that the modification of polar molecular chains can improve the interface interaction between GO and PVA and the dispersion of GO in PVA.The oxygen permeability tests show that the five polar molecular chains can enhance the gas barrier effect of GO on PVA,and the barrier properties of nanocomposites are as follows:TEPA-GO/PVA<ODA-GO/PVA<DETA-GO/PVA<TETA-GO/PVA<NH₂PEG-GO/PVA,among which NH₂PEG-GO has the best enhancement effect on PVA barrier properties.When the loading was 0.75wt%,the oxygen permeability coefficient of NH₂PEG-GO/PVA is0.42×10^-16cm³·cm/(cm²·s·Pa),which is 97.04wt%lower than that of pure PVA.(3)Molecular simulation results show that the modification of grafted polar molecular chains increases the interface interaction between GO and PVA,restricts the movement of interfacial polymer chains,attracts polymer chains to pile up and fold on the surface of GO,forming a dense interfacial layer,reduces the free volume fraction and oxygen permeability of the interface layer.In addition,the structure and performance of the interface layer are affected by the graft chain length,polarity and flexibility.Molecular simulation results show that the polar molecular chains increase the interface interaction between GO and PVA,limit the movement of the interface polymer chains,attract the stacking and folding of the interface polymer chains,forming a dense interface layer,(4)Based on the three-phase structure model of nanocomposite,a gas permeability model considering the characteristics of the interface layer was constructed by combining the thickness and permeability of the interface layer obtained by molecular simulation with the existing macroscopic analysis model.The calculated results are in good agreement with the experimental data.