Vo, Minh Nguyen
(2020)
Quantum Chemical Studies of Reaction Pathways and Thermophysical Properties of Materials.
Doctoral Dissertation, University of Pittsburgh.
(Unpublished)
Abstract
Owing to developments in computer power and algorithmic efficiencies, quantum chemical methods have become essential tools for both fundamental scientific research and industrial problem solving. Quantum mechanics is routinely used in multiple industries including pharmaceuticals, polymers, specialty chemical production, and national defense. Knowledge of reaction pathways and material properties are essential for improving and developing new materials and processes. This dissertation consists of three major projects that employ quantum chemical methods to provide insight into important chemical and physical processes.
The first project elucidated the cationic polymerization mechanism of polyisobutylene. Polyisobutylenes have been produced industrially for over 60 years, but no validated molecular-level understanding of the reaction mechanism exists. With the aid of a powerful reaction pathway finding technique, the growing string method (GSM), we identified an initiator complex that produces low-energy barrier pathways for both initiation and propagation steps. Additionally, we found that it is the extreme acidity of the complex that is crucial for initiating the reaction of polyisobutylene.
The second project studied the reaction mechanism between dimethyl methyl phosphonate (DMMP), a chemical warfare agent (CWA) simulant and different Zr6-based metal-organic frameworks (MOFs). It has been shown experimentally that MOFs containing zirconium secondary building units (SBUs), such as Zr6O4(OH)4 found in UiO-67 and related MOFs, are highly active for neutralizing both DMMP and actual CWAs. We used both fully periodic models and cluster models to study reaction pathways on UiO-67 with multiple defects per SBU. We found that multiple defects can dramatically lower the reaction barrier for DMMP decomposition. Additionally, we found that UiO-67 with multiple defects has lower reaction barriers than Zr-based MOFs having zirconium sites that are inherently undercoordinated due to a lower number of linkers per SBU.
In the third project, we presented a formalism for accurate estimation of dipole moments for complex molecules having conformational degrees of freedom. Dipole moments of complex molecules are often needed for use in correlations for estimating viscosities and other thermophysical properties. We showed that proper accounting of the conformation-dependent dipole moment may be required to achieve an acceptably accurate estimate of the experimental dipole moment.
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Details
| Item Type: |
University of Pittsburgh ETD
|
| Status: |
Unpublished |
| Creators/Authors: |
|
| ETD Committee: |
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| Date: |
30 July 2020 |
| Date Type: |
Publication |
| Defense Date: |
9 March 2020 |
| Approval Date: |
30 July 2020 |
| Submission Date: |
9 March 2020 |
| Access Restriction: |
1 year -- Restrict access to University of Pittsburgh for a period of 1 year. |
| Number of Pages: |
104 |
| Institution: |
University of Pittsburgh |
| Schools and Programs: |
Swanson School of Engineering > Chemical Engineering |
| Degree: |
PhD - Doctor of Philosophy |
| Thesis Type: |
Doctoral Dissertation |
| Refereed: |
Yes |
| Uncontrolled Keywords: |
Reaction mechanisms, Polymerization, Catalysts, Chemical reactions, Inorganic, carbon compounds, Viscosity, Polarity, Metal organic frameworks |
| Date Deposited: |
30 Jul 2020 18:33 |
| Last Modified: |
30 Jul 2021 05:15 |
| URI: |
http://d-scholarship.pitt.edu/id/eprint/38318 |
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