Investigation of Nanostructure Characterizations and Pervaporation Separation Performance of Cross-Linked Chitosan/Graphene Oxide Mixed Matrix Membranes via Molecular Simulation

A multi-scale simulation techniques combined molecular dynamics (MD) and certain quantum mechanics calculations were used to investigate the nanostructural features and transport behavior of the crosslinked chitosan (CS)/graphene oxide (GO) mixed matrix membrane (MMM). In recent years this kind of composite membranes is regarded as a promising one to overcome the inevitable tradeoff of the pervaporation separation performance in polymeric materials. The CS membrane comprises a large quantity of hydrophilic groups to attract polar molecules, and the incorporated GO sheets with high speed water channels can further enhance the water affinity, improving the performance of pervaporation applications. The crosslinked structures are formed by adding the crosslinker glutaraldehyde (GA) to reduce the swelling effect. The synegestic effects of GO fillers on membrane structures and transport behavior are studied via simulation methods in this thesis. However, it is still a challenge to construct MMMs model efficiently and to predict their performance precisely due to the complex structures. In this study we build a new scheme combining molecular scale and quantum scale to achieve the modeling works of MMMs strategically. Meanwhile, the pure CS polymeric membrane and the crosslinked CS membrane were also studied and modeled in advance to verify the simulation methods. As a result, the properties of simulated models agreed well with experimental works. Finally, we estimated and compare the separation performance of the different membrane models by exploring the adsorption isotherm and the self-diffusion process of water, ethanol, and isopropanol vapor molecules within the membrane materials.