Persistent Link:
http://hdl.handle.net/10150/289720
Title:
Cross-linking polymerization of hydrated lipid bilayers
Author:
Liu, Sanchao
Issue Date:
2001
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
The objective of this work was to investigate the cross-linking polymerization of lipids in supramolecular assemblies in order to stabilize the assembly structures. One approach to obtain a cross-linked polymer is by addition of a cross-linking agent. Homobifunctional lipids with two polymerizable groups, one in each of the two hydrophobic chains, can serve as a cross-linking agent. The lipids chosen were dienoyl-substituted lipids, mono- and bis-DenPC, where the reactive diene group is located near the glycerol backbone of the lipids. MonoDenPC 16,18 and bisDenPC18,18 were synthesized. Redox initiation was used to polymerize mixed mono/bisDenPC vesicles. To test the stability of the polymeric vesicles, Triton X-100 (TX-100) was added to the sample and the size determined by quasi-elastic light scattering (QELS). The stability of polymerized LUV to TX-100 depended on the initial composition of the LUV. It was found that 15 mol % bis-substituted lipids, bisDenPC, were needed for cross-linking polymerization. The capability of varying the cross-linking density in these poly(lipid) structures provides researchers with a means to further modify the physical properties of these polymers and membranes. Another approach to achieve cross-linking utilizes heterobifunctional lipids, which have two different reactive groups in one of the lipid tails. These heterobifunctional lipids formed bilayer vesicles or lamellar structures. The properties of the vesicles could be varied by the polymerization of the reactive groups. The design of heterobifunctional monomers allowed either simultaneous or selective polymerization of these groups. The difference in reactivity as well as the difference in polarity of each group also made possible selective polymerization of these reactive groups. Simultaneous polymerization of both reactive groups was achieved by either redox polymerization or direct photoirradiation. UV polymerization showed the formation of oligomers, which dissolved in organic solvents and TX-100. On the other hand, redox polymerization gave cross-linked polymers, which were insoluble in most organic solvents and stable towards addition of TX-100. The cross-linking density could be varied by choosing different polymerization techniques. Electron micrographs of the cross-linked polymeric vesicles showed they could retain their size and shape after freeze-drying and re-dispersal in water. The surface of the cross-linked vesicles could be modified for many applications.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Chemistry, Organic.; Chemistry, Pharmaceutical.; Chemistry, Polymer.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Graduate College; Chemistry
Degree Grantor:
University of Arizona
Advisor:
O'Brien, David F.

Full metadata record

DC FieldValue Language
dc.language.isoen_USen_US
dc.titleCross-linking polymerization of hydrated lipid bilayersen_US
dc.creatorLiu, Sanchaoen_US
dc.contributor.authorLiu, Sanchaoen_US
dc.date.issued2001en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractThe objective of this work was to investigate the cross-linking polymerization of lipids in supramolecular assemblies in order to stabilize the assembly structures. One approach to obtain a cross-linked polymer is by addition of a cross-linking agent. Homobifunctional lipids with two polymerizable groups, one in each of the two hydrophobic chains, can serve as a cross-linking agent. The lipids chosen were dienoyl-substituted lipids, mono- and bis-DenPC, where the reactive diene group is located near the glycerol backbone of the lipids. MonoDenPC 16,18 and bisDenPC18,18 were synthesized. Redox initiation was used to polymerize mixed mono/bisDenPC vesicles. To test the stability of the polymeric vesicles, Triton X-100 (TX-100) was added to the sample and the size determined by quasi-elastic light scattering (QELS). The stability of polymerized LUV to TX-100 depended on the initial composition of the LUV. It was found that 15 mol % bis-substituted lipids, bisDenPC, were needed for cross-linking polymerization. The capability of varying the cross-linking density in these poly(lipid) structures provides researchers with a means to further modify the physical properties of these polymers and membranes. Another approach to achieve cross-linking utilizes heterobifunctional lipids, which have two different reactive groups in one of the lipid tails. These heterobifunctional lipids formed bilayer vesicles or lamellar structures. The properties of the vesicles could be varied by the polymerization of the reactive groups. The design of heterobifunctional monomers allowed either simultaneous or selective polymerization of these groups. The difference in reactivity as well as the difference in polarity of each group also made possible selective polymerization of these reactive groups. Simultaneous polymerization of both reactive groups was achieved by either redox polymerization or direct photoirradiation. UV polymerization showed the formation of oligomers, which dissolved in organic solvents and TX-100. On the other hand, redox polymerization gave cross-linked polymers, which were insoluble in most organic solvents and stable towards addition of TX-100. The cross-linking density could be varied by choosing different polymerization techniques. Electron micrographs of the cross-linked polymeric vesicles showed they could retain their size and shape after freeze-drying and re-dispersal in water. The surface of the cross-linked vesicles could be modified for many applications.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectChemistry, Organic.en_US
dc.subjectChemistry, Pharmaceutical.en_US
dc.subjectChemistry, Polymer.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.disciplineChemistryen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorO'Brien, David F.en_US
dc.identifier.proquest3026579en_US
dc.identifier.bibrecord.b42177777en_US
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