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Lasar Dissertation 202610.18 MB
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Dissertation
Designing the designer solvent: investigation of thermal and structural behaviors of ionic liquids
University of Iowa
Doctor of Philosophy (PhD), University of Iowa
Spring 2026
DOI: 10.25820/etd.008356
Abstract
Ionic liquids (ILs) are liquid molecular salts which have melting points below 100 °C that have gained significant attention due to their advantageous physicochemical properties for industrial applications such as chemical separations, anti-corrosion, tribology, drug delivery, energy storage, and fuel cells. IL properties can be precisely tuned by modifying the ion structure, functional groups, ion pairing, or the addition of a co-solvent, making them highly versatile solvents. Understanding how changing the molecular structure of ILs effects these properties under different stimuli is vital for optimizing IL application designs. This dissertation presents fundamental studies of IL behaviors in bulk and interfacial environments as well as in the presence of a cosolvent. This is accomplished through the combined use of calorimetry and spectroscopic analytical techniques.
The primary aim of this work is to determine how changing the IL structure and mixing at various dilutions in molecular co-solvents in affects the phase transition pathways and resulting structures. Understanding thermal phase change behaviors of ILs and IL mixtures are fundamentally interesting and pertinent to their performance as a solvent. Differential scanning calorimetry and temperature-controlled Fourier Transform infrared spectroscopy revealed IL+cosolvent mixtures display eutectic behavior and display new phase transitions not observed in either neat component.
The second aim of this work is to investigate how changing the IL ion symmetry affects the structural and dynamic behavior of ILs at the interface using ellipsometry in tandem with infrared reflection absorption spectroscopy. Understanding what components of the molecular structure cause the greatest impact of this behavior and to what extent is critical to surface applications such as lubrication or electrochemical applications. Results show increasing the ion asymmetry increases the interfacial long-range structural ordering of IL ions in thin films.
The outcomes of this work enhance the overall understanding of how the molecular structure effects IL behavior in response to shear, solvent dilution, and thermal stimuli at the interface and in bulk. These results provide valuable insight into IL application design especially those involving interfaces or thermal fluctuations such as lubrication, energy storage, and fuel cells.
Details
- Title: Subtitle
- Designing the designer solvent: investigation of thermal and structural behaviors of ionic liquids
- Creators
- Colleen Barbara Lasar
- Contributors
- Scott K Shaw (Advisor)Mark A Arnold (Committee Member)Christopher M Cheatum (Committee Member)Johna Leddy (Committee Member)Elizabeth A Stone (Committee Member)
- Resource Type
- Dissertation
- Degree Awarded
- Doctor of Philosophy (PhD), University of Iowa
- Degree in
- Chemistry
- Date degree season
- Spring 2026
- DOI
- 10.25820/etd.008356
- Publisher
- University of Iowa
- Number of pages
- xxiii, 255 pages
- Copyright
- Copyright 2026 Colleen Barbara Lasar
- Language
- English
- Date submitted
- 04/28/2026
- Description illustrations
- illustrations, graphs, tables
- Description bibliographic
- Includes bibliographical references (pages 187-198).
- Public Abstract (ETD)
The chemicals we use in our daily lives and in industry have a profound impact on the environment. Since the mid-20th century, with the rise of the green chemistry movement and the establishment of the U.S. Environmental Protection Agency (EPA), researchers have been actively searching for safer, more sustainable, eco-friendly alternatives for applications such as anti-corrosion, lubrication, batteries, and space technologies. In recent decades, ionic liquids (ILs) have emerged as a promising candidate as alternative solvents for such applications. ILs are a class of molecular salts that, unlike traditional salts such as table salt (sodium chloride), are liquid at or near room temperature. Their physical and chemical properties, such as viscosity or melting point, can be precisely tuned by modifying their molecular structure or ion pairings. This makes them highly versatile solvents and thus has been widely deemed as “designer solvents”.
As researchers design and optimize new systems for various applications, it is imperative to understand how materials behave at different temperatures, purities, or confinement. Previous studies have investigated how changing the molecular structure affects IL behavior in pure bulk solutions. However many IL applications involve interfaces, a region where two materials meet, such as lubricants confined between gears or electrodes in batteries. Chemicals are known to behave differently at or near interfaces or under confinement, so it is imperative to study how ILs behave under such environments. Also, many applications, such as energy storage, require further tuning of ILs through the addition of a solvent. While certain behaviors have been studied at room temperature, little is known about their behavior at lower temperatures, such as phase transitions, which is crucial as some applications are subject to cold climate conditions.
Therefore, this work takes a systematic approach to investigate how the molecular structure and ion pairing of ILs affect their behavior in both thin films and bulk fluids under various temperatures and compositions. This provides insight into how ILs organize themselves near interfaces and IL mixture phase transition behavior (such as freezing and melting), what temperatures those phase transitions occur, and how the ions arrange themselves within the resulting structure
- Academic Unit
- Chemistry
- Record Identifier
- 9985176974202771
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