Preparation And Oxygen Barrier Property Of Functionalized Graphene Oxide/Poly(Vinyl Alcohol) Composites

Nowadays,energy shortage and environmental pollution is increasingly serious.Poly（vinyl alcohol）（PVA）has promising applications in packaging fields such as food,medicine,electronics,aerospace due to its aboudant sources,biodegradability and good film-formation property.However,its poor oxygen barrier property is difficult to meet the need of practical engineering.Therefore,it is urgent to develop high oxygen barrier PVA-based materials.In this paper,graphene oxide（GO）was modified using covalent and non-covalent method,respectively.Then,the modified GO was blended with PVA to prepared PVA nanocomposites.Effects of modified GO on the microstructure,thermal properties and oxygen barrier propertys of PVAnanocomposites were studied in detail,and the mechanism that modified graphene oxide enhance the oxygen barrier property of PVA was further studied using molecular simulation.The main contents are as follows:（1）GO was modified to obtain modified graphene oxide(Tris-GO,TA-GO and Zn²⁺-GO)using tris（hydroxymethyl）aminoethane（Tris）,tannic acid（TA）and zinc ion(Zn²⁺),respectively.The results of FT-IR confirms that GO were successfully functionalized.XRD and AFM demonstrate that the interlayer spacing and thickness of the modified graphene oxide increase in order as following:TA-GO>Tris-GO>Zn²⁺-GO>GO;SEM images show that the deposited of GO was more loosely packed.（2）Tris-GO,TA-GO and Zn²⁺-GO as fillers were incorporated into PVA by solution blending to fabricate nanocomposites(Tris-GO/PVA,TA-GO/PVA,Zn²⁺-GO/PVA and Zn²⁺-GO/CMC-PVA),respectively.The results of FT-IR and DSC confirm that Tris-TA-and Zn²⁺-modification can enhance the interfacial adhesion of GO and PVA.The SEM results show that the Tris-and TA-modification improves the dispersion of GO in PVA matrix and the compatibility with PVA matrix.By comparison,TA-GO has better dispersion in PVA;and e the Zn²⁺-modification of improves the distribution of GO in PVA.Permeability test results show that surface modifications improves the enhancing effect of GO on the barrier properties of PVA.The oxygen permeability coefficient of composites follows in order:Zn²⁺-GO/CMC-PVA<Zn²⁺-GO/PVA<TA-GO/PVA<Tris-GO/PVA,indicating that nanocomposites filled with Zn²⁺-GO have the best barrier properties.In the case of 0.75wt%Zn²⁺-GO,the oxygen permeability of Zn²⁺-GO/CMC-PVA and Zn²⁺-GO/PVA can be reduced by 97.9%and 97.3%compared with the pure PVA,respectively.（3）Molecular dynamics（MD）and Monte Carlo（MC）methods were used to simulate the diffusion and adsorption of oxygen molecules in modified GO/PVA composites.The results show that the diffusion is dominant the permeation of oxygen in PVA nanocomposites.The diffusion is mainly influenced by free volume fraction and distribution.The diffusion coefficient of oxygen in the nanocomposites is in order as following:Zn²⁺-GO/PVA<TA-GO/PVA<Tris-GO/PVA<GO/PVA<PVA.This indicates that the dispersion and distribu-tion of GO in PVA has an key effect of permeability of nanocomposites.has a main effect on the free volume distribution considering the principle of GO modification.In conclusion,the barrier property of the composite can be enhanced more effectively by controlling the dispersion and distribution of the GO in PVA.