Haro Mares, Nadia Berenice (2024)
Study of Ethylene Glycol Dynamics Confined in Decorated SBA-15 and Novel Radicals.
Technische Universität Darmstadt
doi: 10.26083/tuprints-00027474
Ph.D. Thesis, Primary publication, Publisher's Version
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Item Type: | Ph.D. Thesis | ||||
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Type of entry: | Primary publication | ||||
Title: | Study of Ethylene Glycol Dynamics Confined in Decorated SBA-15 and Novel Radicals | ||||
Language: | English | ||||
Referees: | Buntkowsky, Prof. Dr. Gerd ; Gutmann, apl. Prof. Torsten | ||||
Date: | 25 July 2024 | ||||
Place of Publication: | Darmstadt | ||||
Collation: | 116 Seiten in verschiedenen Zählungen | ||||
Date of oral examination: | 27 May 2024 | ||||
DOI: | 10.26083/tuprints-00027474 | ||||
Abstract: | This research project is structured into two main parts: i) Investigation of the dynamics of small molecules within confined pore spaces (mesoporous silica). ii) Evaluation of new radicals as polarization transfer agents to enhance the sensitivity of nuclear magnetic resonance (NMR). In the first part of this study, the research focuses on understanding how the presence of 3- aminopropyl triethoxysilane (APTES) functional groups, attached to the pore walls of amorphous Santa Barbara material (SBA- 15), influences the behavior of partially deuterated ethylene glycol (EG- d₄) as the guest molecule. While the significant influence of functional groups on molecules confined within mesoporous silica pores is known, the details of the interaction at the solid-liquid interface are not fully understood. This investigation involves the analysis of three distinct systems: EG- d₄ in the bulk, EG- d₄ confined within pure SBA- 15, and EG- d₄ confined within APTES-modified SBA- 15. Importantly, both mesoporous materials have similar pore sizes, allowing any differences in the guest molecule's dynamics to be attributed primarily to the presence of the APTES functional group. Differential scanning calorimetry (DSC) analysis reveals the crystallization of EG- d₄ within the APTES-modified material. The influence of the surrounding on the crystallization primarily occurs due to the formation of hydrogen bonds between various surface groups in the material (-OH and -NH₂) and the hydroxyl groups of EG- d₄. This change in the molecular alignment promotes the EG- d₄ crystallization during the recorded slow and rapid heating/cooling cycles, when compared to EG- d₄ in unmodified SBA- 15 or EG- d₄ in its bulk phase. Additionally, an analysis of the ²H solid-state Nuclear Magnetic Resonance (²H ssNMR) spectra, acquired at various temperatures for EG- d₄ confined within APTES-functionalized SBA- 15, reveals two distinct components at temperatures in the region of the phase transition. These components consist of a Lorentzian-shaped line, representing a liquid-like phase, and a Pake pattern representing a solid-like phase. In summary, variations in molecular interactions due to different environmental conditions lead to differing activation energy distributions of the phase transitions in the three systems under investigation. The second part of this work focuses on testing the effectiveness of new polarization agents (PAs) for Dynamic Nuclear Polarization (DNP) designed for potential use in biological applications. The stability of some of these novel radicals is assessed under biological pH conditions, demonstrating that they preserve their original structure and remained capable of serving as polarization transfer agents. Furthermore, it is determined that certain substituent groups within the radical structures led to the formation of conformers. These conformers, in turn, reduce the efficiency of these PAs when employed in solid-state DNP experiments. |
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Status: | Publisher's Version | ||||
URN: | urn:nbn:de:tuda-tuprints-274748 | ||||
Classification DDC: | 500 Science and mathematics > 540 Chemistry | ||||
Divisions: | 07 Department of Chemistry > Eduard Zintl-Institut > Physical Chemistry | ||||
Date Deposited: | 25 Jul 2024 12:08 | ||||
Last Modified: | 29 Jul 2024 11:52 | ||||
URI: | https://tuprints.ulb.tu-darmstadt.de/id/eprint/27474 | ||||
PPN: | 520175433 | ||||
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