Liquid crystals possess both order and mobility. Hydrated, natural and synthetic amphiphiles self-organize to form various liquid crystal phases as a function of molecular structure, temperature, concentration, and pressure. Self-organization is the ordering of molecules via non-covalent interactions, i.e. hydrogen bonding, van der Waals, pi-pi interactions, ionic interactions, hydrophobic short-range forces, and London dispersion forces. Amphiphiles contain both polar and non-polar moieties. In general, amphiphiles are composed of a polar, hydrophilic headgroup and one or more non-polar, hydrophobic tail(s). At equilibrium, the unfavorable enthalpic interaction of the polar water molecules with the non-polar amphiphile tails is minimized by the aggregation of the latter with the non-polar tails of other amphiphiles to form a water excluded hydrophobic block, while the hydrophilic headgroups line the interface of the phase-separated aqueous domains. Self-supported arrays of self-organized, hydrated amphiphile assemblies include lamellar/vesicles, various normal and inverted cubic phases, and normal and inverted hexagonal phases. The inverted hexagonal (HII) phase can be considered as aqueous columns patterned in a hexagonal fashion. The polar amphiphile headgroups are well ordered at the water-amphiphile interface, while their non-polar tails are disordered and fill the area between the aqueous water channels. In general, amphiphiles with two or more non-polar chains and a small, poorly hydrated headgroup favor the formation of the HII phase. Longer tails or the incorporation of bulky design elements, i.e. cis-double bonds or branching substituents, in the amphiphile tail(s) lowers the temperature associated with the formation of the HII phase. Several HII-forming amphiphiles have been designed and synthesized. Upon hydration, the phase behavior of these amphiphiles was evaluated by 31P-NMR assembly characterization. Radical polymerizations were used to stabilize the HII phase assemblies resulting in cross-linked polymer networks. The cross-linked materials displayed dramatically different physical properties, i.e. lowered solubility in common organic solvents. The polymer assembly phase behavior was evaluated via 31P-NMR after polymerization. A synthetic route to phosphoethanolamines via a novel di-protected glycerophosphoethanolamine has been designed and developed. A phosphoethanolamine lipid has been synthesized using this route. The route appears to be general to the synthesis of any phosphoethanolamine.
| Identifer | oai:union.ndltd.org:arizona.edu/oai:arizona.openrepository.com:10150/280149 |
| Date | January 2002 |
| Creators | Arzberger, Steven C. |
| Contributors | O'Brien, David F. |
| Publisher | The University of Arizona. |
| Source Sets | University of Arizona |
| Language | en_US |
| Detected Language | English |
| Type | text, Dissertation-Reproduction (electronic) |
| 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. |
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