Text

theses

Ionic liquids (ILs) are salts in the liquid state near room temperature. Composed of cations and anions, ILs can be designed as needed by chemically modifying the structure of the ions. Finding the connection between the molecular structures and physical and chemical properties of ILs allows us to choose an existing IL or synthesize one based on the task. The current thesis contributes to the understanding of IL structure both in bulk and at interfaces, as well as dynamics properties of ILs.

This thesis comprises three major sections. The first section examines the bulk structure of ILs with various cations and fluorinated anions. The second section studies the diffusion behavior of charged cations and anions in ILs and the diffusivity of neutral molecules in IL-solvent mixtures. The third section focuses on the structure of ILs in vacuum studied by molecular dynamics (MD) simulations. Structure factors of the liquids were measured using high energy X-ray scattering (XRS) method and calculated from MD simulations. The diffusivity of molecules in ILs were measured using NMR experiments. It is found that the physical properties and bulk structure of ILs are related to their molecular structures. For ILs with long cationic alkyl tails and anionic fluorinated tails, the tails alternate along the charge network and form nonpolar domains. The diffusivity of ILs can be affected by many factors, including ion's size, shape and conformational flexibility. The heterogeneity structure of ILs renders that neutral molecules diffuse faster than the hydrodynamic prediction. Structure of ILs in vacuum is very different from their bulk structure, which is affected by the nonpolar tail length, box size and electric fields.

ETD_10618

Ph.D.

Includes bibliographical references

doi:10.7282/t3-hasy-wx40

ETD doctoral

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