Molecular Dynamics Simulation On Pickering Emulsion Stabilized By Switchable Surfactant And Inclusion By Cyclodextrin

There are many physical phenomena in nature,such as adsorption,aggregation,deposition and so on.For a long time,many scientists have been exploring and studying a series of physical processes continuously.The study of the mechanism of a variety of physical processes and the understanding of the interaction mechanism in the process can not only help to guide the theory of experiment and production practice,but also explain a series of related experimental phenomena.In this thesis,the physical processes of molecular inclusion of surfactant stabilized Pickering emulsion and cyclodextrin are studied by molecular simulation,and the microscopic mechanism of these processes is explained from the molecular level,which has important guiding significance for practical application.This paper mainly includes the following three parts:The first part:Molecular Dynamics（MD）simulation method was used to explore the reversible emulsification/demulsification mechanism of Pickering emulsion stabilized by nano-silica particles（NPs）and CO₂ switching surfactant N-（3（dimethylamino）propyl）alkylamide（CPMA）.The corresponding CPMA and CPMAH⁺systems are constructed,and the behaviors of NP at the oil-water interface in CPMA and CPMAH⁺systems are compared,and the interaction forces between them and the related data such as charge distribution and three-phase contact angle are calculated.The results show that NP binds firmly to the oil-water interface mainly through electrostatic force and CPMAH⁺to form a stable oil-in-water Pickering emulsion.After deprotonation,the binding of NP to CPMA is unstable and the emulsion equilibrium is broken.The second part:The reversible emulsification/demulsification mechanism of Pickering emulsion stabilized by nano-silica particles and CO₂ switching surfactant N-dodecyl-N-dimethylacetamidine（DDA）was discussed by Molecular Dynamics simulation（MD）.The corresponding DDA and DDAH⁺systems are constructed,and the behavior of NP at the oil-water interface in DDA and DDAH⁺systems is compared,and the electrostatic force,charge distribution and three-phase contact angle between them are calculated.The results show that NP binds firmly to the oil-water interface mainly through electrostatic force and DDAH⁺to form a stable oil-in-water Pickering emulsion.After deprotonation,the binding of NP and DDA is unstable and the demulsification process is realized.The third part:Molecular Dynamics simulation was used to study the interaction of hostβ-cyclodextrin（β-CD）,hydroxypropyl-β-cyclodextrin（HP-β-CD）and sulfonbutyl-β-cyclodextrin（SBE-β-CD）inclusion compound anthracene（ANT）.The effects of different substituents on the conformational change and inclusion degree of cyclodextrin inclusion complex were studied.The results show that all three kinds of cyclodextrins can bind ANT,because the flexibility of sulfobutyl will lead to self-closure of the narrow rim,ANT can only enter the cavity from the wide rim of SBE-β-CD.The configuration of the inclusion complex formed by HP-β-CD and SBE-β-CD with ANT changed more greatly,and the hydrophobic cavity of HP-β-CD and SBE-β-CD was enlarged,and the degree of inclusion was closer than that of naturalβ-CD.