Dissertation
Spectroscopic analysis of molecular fluids at the solid-liquid interface
University of Iowa
Doctor of Philosophy (PhD), University of Iowa
Autumn 2017
DOI: 10.17077/etd.afg6mvxl
Abstract
<p>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.</p>
<p>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.</p>
<p>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.</p>
Details
- Title: Subtitle
- Spectroscopic analysis of molecular fluids at the solid-liquid interface
- Creators
- Samantha Lynn Nania - University of Iowa
- Contributors
- Scott K. Shaw (Advisor)Sarah C. Larsen (Committee Member)Johna Leddy (Committee Member)Alexei V. Tivanski (Committee Member)Sara E. Mason (Committee Member)
- Resource Type
- Dissertation
- Degree Awarded
- Doctor of Philosophy (PhD), University of Iowa
- Degree in
- Chemistry
- Date degree season
- Autumn 2017
- DOI
- 10.17077/etd.afg6mvxl
- Publisher
- University of Iowa
- Number of pages
- xvii, 145 pages
- Copyright
- Copyright © 2017 Samantha Lynn Nania
- Language
- English
- Date submitted
- 05/04/2018
- Description illustrations
- illustrations (some color)
- Description bibliographic
- Includes bibliographical references (pages 141-145).
- Public Abstract (ETD)
The layer of material present where a solid and a liquid meet is called an interface, and interfaces play an important role in many everyday applications like lubrication, transportation, and even bacterial infections. Understanding the chemical and physical properties of the microscopic interface will help scientists to making better materials more efficiently and improve the quality of life for everyone. Studying this chemical interface is very challenging because the dimension of these regions are very small, on the scale of 1/1000 of a human hair, so this work uses reflected light to study the formation of thin liquid films on a solid, mirror-like surface. This research aims to improve our understanding of how liquids slip, stick, or pack when it is very near the solid, within the interface.
Our results show that some fluids can slip completely from a surface, which changes the way scientists and engineers approach challenges in lubrication, transportation, and even bacterial infections. We also learned that other solid-liquid combinations create fluid films that have tunable behavior for varying size of the molecules or with varying film thicknesses. This gives future scientists and engineers new ways to control properties of the interface, and will allow improved performance for future devices like ships and medical implants.
Future studies in this area of chemistry will shed lights on the behavior of the molecules at this microscopic interface and continue to uncover chemical interactions that have impacts on industrial, commercial, and basic research applications.
- Academic Unit
- Chemistry
- Record Identifier
- 9983777266402771
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