Date of Degree
PhD (Doctor of Philosophy)
Shaw, Scott K.
First Committee Member
Larsen, Sarah C.
Second Committee Member
Third Committee Member
Tivanski, Alexei V.
Fourth Committee Member
Mason, Sara E.
Chemical and physical interactions play important roles in surface film formation and fluid slip at the fluid-solid interface. It has been shown that the fluid molecules at this solid interface behave differently than the molecules in the bulk. To investigate fluid film formation and the fluid’s transition between bulk and interfacial regions, a dynamic wetting technique is utilized. This technique allows the formation of variable thickness fluid films. When used in conjunction with vibrational spectroscopy and ellipsometry, direct analysis of variable thicknesses films, spanning the bulk to interfacial transition, can be obtained. Film thickness are predicted using the Landau-Levich model and the Lifshitz model, and comparisons generally agree with experimental results.
According to hydrodynamic no slip boundary condition, fluid molecules near a solid surface can have no velocity with respect to the solid substrate. Recent theories state more specifically that, if a fluid comes in contact with an ultra-smooth surface (< 5-7 nm RMS roughness), the no slip boundary condition might be violated. We confirmed violation of the no slip boundary condition in two specific cases for fluid layers on SAM-modified substrates. To understand how the fluid/solid properties affect this condition, an acetophenone and bare silver surface was studied. Our results show that the structure and ordering of fluid molecules within these films are highly dependent on the film’s thickness and confinement. Temperature control wetting studies also corroborate with these results showing that as a frozen film of large thickness approaches the melting point, a molecular reorganization occurs creating a crystalline structure before the film melts into an isotropic bulk structure. Structure dependence on alkyl-chain length was then investigated using a series of trialkylamine fluids. Results show significant changes in the vibrational profile as a function of film thicknesses and rotational velocity as the alkyl-chains increase in length. These are ascribed to changes in primary carbon attached to the nitrogen as a function shearing and the rigidity of the molecule.
These results reveal interactions taking place at the solid-liquid interface and have impacts on a broad spectrum of industrial, commercial, and research applications including lubrication and transportation vehicles.
boundary condition, films, molecular fluids, ordering, surfaces, wetting
xvii, 145 pages
Includes bibliographical references (pages 141-145).
Copyright © 2017 Samantha Lynn Nania
Nania, Samantha Lynn. "Spectroscopic analysis of molecular fluids at the solid-liquid interface." PhD (Doctor of Philosophy) thesis, University of Iowa, 2017.