Dissertation
POLYMER DYNAMICS: MEMBRANE INTERACTION & PHOTO-MECHANICS
Doctor of Philosophy (PhD), Washington State University
01/2015
Handle:
https://hdl.handle.net/2376/117032
Abstract
This body of work addresses two different aspects of polymer dynamics that span the biophysical and photomechanical domains. The first section is devoted to the interaction of a polyelectrolyte with supported lipid bilayers for application in gene-delivery systems. Lipid bilayers provide a protective layer for cells as well as hosting the machinery for transport across the cell membrane. Characterizing the chemical interactions on the surface of the cell and measuring response to thermal fluctuations or other external forces is of great interest. This study uses single particle tracking (SPT) and fluorescence recovery after photo-bleaching (FRAP) to reveal the kinetic and thermodynamic properties of branched polyethylenimine (PEI) as it attaches to, and diffuses in, different solid supported lipid bilayers including DMPC (1,2-dimyristoyl-sn-glycero-3-phosphocholine) and POPC (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine). These properties were studied as a function of lipid composition, pH, temperature, and phase. The experiments were performed at 15°C and 25°C, and for each temperature, data was collected at pH 6.5, 7.4 and 8.5.
In the second section we investigate shape memory polymers that can be optically actuated due to a photomechanical effect observed upon isomerization of an azo bond. The polymer contains light-sensitive azobenzene, which can lead to photo-contraction of the polymer by converting optical energy to mechanical energy. Here, we have synthesized a new photo-responsive polymer consisting of a polyhedral oligomeric silsesquioxane (POSS) core functionalized with eight identical polymer arms. These were grafted to polylactides (PLAs) of length 20 via ring opening polymerization of d, l-lactide to yield a star-branched macromer POSS-(PLA20)8. The reactive hydroxyl end groups were then cross-linked with azobenzene units to form a POSS-Azo photo-responsive polymer. The structure of the cross-linker, core, and polymer, were characterized by IR and NMR. Exposure to 405 nm light isomerized the trans isomers to cis, which happens in a matter of seconds. The reaction is reversible with heat. The thermal relaxation of the cis isomer to trans is much slower.
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Details
- Title
- POLYMER DYNAMICS: MEMBRANE INTERACTION & PHOTO-MECHANICS
- Creators
- Seyedeh Samaneh Tabatabaei
- Contributors
- James A. Brozik (Advisor)Fred Gittes (Committee Member)Ursula Mazur (Committee Member)Susan Dexheimer (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Materials Science and Engineering Program
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Number of pages
- 176
- Identifiers
- 99900581730201842
- Language
- English
- Resource Type
- Dissertation