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A Study of Amorphous Materials: Surface Dynamics, Surface Modification, and Polyamorphism.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	A Study of Amorphous Materials: Surface Dynamics, Surface Modification, and Polyamorphism./
作者:	Li, Yuhui.
出版者:	Ann Arbor : ProQuest Dissertations & Theses, : 2022,
面頁冊數:	224 p.
附註:	Source: Dissertations Abstracts International, Volume: 83-12, Section: B.
Contained By:	Dissertations Abstracts International83-12B.
標題:	Pharmaceutical sciences. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=29215166
ISBN:	9798802750681

A Study of Amorphous Materials: Surface Dynamics, Surface Modification, and Polyamorphism.
Li, Yuhui.

A Study of Amorphous Materials: Surface Dynamics, Surface Modification, and Polyamorphism. - Ann Arbor : ProQuest Dissertations & Theses, 2022 - 224 p.

Source: Dissertations Abstracts International, Volume: 83-12, Section: B.

Thesis (Ph.D.)--The University of Wisconsin - Madison, 2022.

This item must not be sold to any third party vendors.

The glass is a unique solid state with liquid-like spatial uniformity and crystal-like mechanical strength. Different materials have been prepared into the glassy state for applications in various situations. Nevertheless, glasses are unequilibrated and tend to crystalize. During this process, the dynamics and the structure inside the glasses play a vital role. This thesis is concerned with these two properties, especially the dynamics at the free surface of glasses and the structural change during the polyamorphic transition.The molecular diffusion rate was determined by the method of surface grating decay at the free surface of three glasses, posaconazole, itraconazole, and MTDATA. The results are analyzed along with other molecular glasses without extensive hydrogen bonds. In total, these systems cover a wide range of molecular geometries from rod-like to quasi-spherical to discotic and their surface diffusion coefficients vary by 9 orders of magnitude. This variation can be well explained by the existence of a steep surface mobility gradient and the anchoring of surface molecules at different depths. The survey of surface diffusion was then extended to other glass types. A strong correlation between surface diffusion and the fragility of bulk dynamics was discovered. This trend extends through glasses of all kinds: molecular, polymeric, chalcogenide, silicon, metallic, and oxide. The correlation is attributed to the robustness of covalent network bonds present in strong liquids, making them more resistant to environmental excitation from bulk to surface. The findings help understand and predict surface mobility to develop amorphous materials with high stability for their diverse applications.In real applications, amorphous materials are usually developed by doping multiple components but the effect of composition on surface dynamics remains poorly understood. The surface mobility of amorphous indomethacin was measured using the method of surface grating decay in the presence of moisture and the surfactant Tween 20. It is found that both components significantly enhance the surface mobility, and their effects are well described by the principle of concentration-temperature superposition (CTS); that is, the same surface dynamics is observed at the same Tg-normalized temperature, where Tg the composition-dependent glass transition temperature. The CTS principle allows the prediction of the surface dynamics of multi-component amorphous materials.Due to the fast surface mobility, amorphous drugs can grow crystals much more rapidly at the surface than in the bulk, causing poor stability and slow dissolution of drug products. We show that a nano-coating of chitosan (a pharmaceutically acceptable polymer) can be deposited on the surface of amorphous indomethacin by electrostatic deposition, leading to significant improvement of physical stability, wetting by aqueous media, dissolution rate, powder flow, and tabletability. The coating condition was chosen so that the positively charged polymer deposits on the negatively charged drug. This electrostatic deposition can be used as a general method to manufacture stable amorphous formulations.Other than the surface dynamics, this thesis is also concerned with the bulk structures of amorphous materials. X-ray scattering and solid-state NMR (ssNMR) were used to investigate the structural change during the polyamorphic transition of D-mannitol. We find that the non-polar hydrocarbon groups in D-mannitol changes with density during the conversion, while the structure constructed by hydrogen-bonding is significantly reorganized. The reorganization occurs by rearranging the second coordination shells and beyond, resulting in supramolecular aggregates that give rise to low-angle prepeaks in the scattering pattern. This study provides the structural basis for the phenomenon of polyamorphism.

ISBN: 9798802750681Subjects--Topical Terms:

3173021
Pharmaceutical sciences.
Subjects--Index Terms:

Amorphous materials

A Study of Amorphous Materials: Surface Dynamics, Surface Modification, and Polyamorphism.
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245 1 0 $a A Study of Amorphous Materials: Surface Dynamics, Surface Modification, and Polyamorphism.
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500 $a Source: Dissertations Abstracts International, Volume: 83-12, Section: B.
500 $a Advisor: Yu, Lian.
502 $a Thesis (Ph.D.)--The University of Wisconsin - Madison, 2022.
506 $a This item must not be sold to any third party vendors.
520 $a The glass is a unique solid state with liquid-like spatial uniformity and crystal-like mechanical strength. Different materials have been prepared into the glassy state for applications in various situations. Nevertheless, glasses are unequilibrated and tend to crystalize. During this process, the dynamics and the structure inside the glasses play a vital role. This thesis is concerned with these two properties, especially the dynamics at the free surface of glasses and the structural change during the polyamorphic transition.The molecular diffusion rate was determined by the method of surface grating decay at the free surface of three glasses, posaconazole, itraconazole, and MTDATA. The results are analyzed along with other molecular glasses without extensive hydrogen bonds. In total, these systems cover a wide range of molecular geometries from rod-like to quasi-spherical to discotic and their surface diffusion coefficients vary by 9 orders of magnitude. This variation can be well explained by the existence of a steep surface mobility gradient and the anchoring of surface molecules at different depths. The survey of surface diffusion was then extended to other glass types. A strong correlation between surface diffusion and the fragility of bulk dynamics was discovered. This trend extends through glasses of all kinds: molecular, polymeric, chalcogenide, silicon, metallic, and oxide. The correlation is attributed to the robustness of covalent network bonds present in strong liquids, making them more resistant to environmental excitation from bulk to surface. The findings help understand and predict surface mobility to develop amorphous materials with high stability for their diverse applications.In real applications, amorphous materials are usually developed by doping multiple components but the effect of composition on surface dynamics remains poorly understood. The surface mobility of amorphous indomethacin was measured using the method of surface grating decay in the presence of moisture and the surfactant Tween 20. It is found that both components significantly enhance the surface mobility, and their effects are well described by the principle of concentration-temperature superposition (CTS); that is, the same surface dynamics is observed at the same Tg-normalized temperature, where Tg the composition-dependent glass transition temperature. The CTS principle allows the prediction of the surface dynamics of multi-component amorphous materials.Due to the fast surface mobility, amorphous drugs can grow crystals much more rapidly at the surface than in the bulk, causing poor stability and slow dissolution of drug products. We show that a nano-coating of chitosan (a pharmaceutically acceptable polymer) can be deposited on the surface of amorphous indomethacin by electrostatic deposition, leading to significant improvement of physical stability, wetting by aqueous media, dissolution rate, powder flow, and tabletability. The coating condition was chosen so that the positively charged polymer deposits on the negatively charged drug. This electrostatic deposition can be used as a general method to manufacture stable amorphous formulations.Other than the surface dynamics, this thesis is also concerned with the bulk structures of amorphous materials. X-ray scattering and solid-state NMR (ssNMR) were used to investigate the structural change during the polyamorphic transition of D-mannitol. We find that the non-polar hydrocarbon groups in D-mannitol changes with density during the conversion, while the structure constructed by hydrogen-bonding is significantly reorganized. The reorganization occurs by rearranging the second coordination shells and beyond, resulting in supramolecular aggregates that give rise to low-angle prepeaks in the scattering pattern. This study provides the structural basis for the phenomenon of polyamorphism.
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