Dissertation
Application-driven studies of photomechanical materials
Doctor of Philosophy (PhD), Washington State University
01/2018
Handle:
https://hdl.handle.net/2376/16343
Abstract
Deep brain stimulation therapy is a well-established medical procedure with well-documented benefits, but this procedure would be enhanced by a flexible therapy device that could bend when photoactivated. To this end, two types of materials, which respond to light by inducing a stress and strain, show promise and are therefore selected to be characterized: photomechanical dye-doped glassy polymer fibers and liquid crystal elastomers. A custom designed and built apparatus, the photorheometer, measures the force created by these materials during photostimulation. Using the developed theory, it is found that the liquid crystal elastomers produce a large strain but small stress while dye-doped glassy polymer fibers produce a large stress but small strain.
Photoisomerization in dyes, a mechanism where a molecule changes shape in response to photostimulation, is investigated in dye-doped glassy polymer fibers. Results show glassy polymer fibers doped with isomerizable dyes have a notable polarization dependence, but this dependence cannot be fully explained by isomerization alone, as non-isomerizable dyes also have a polarization dependence.
Liquid crystal elastomers from two synthesis methods are characterized. The first method creates side-chain end-on siloxane-based liquid crystal elastomers, and the second method is a two-stage procedure creating main-chain acrylate-based liquid crystal elastomers. Using the photorheometer, materials made with the different synthesis methods are charactered with various liquid crystalline order. The materials made with the two-stage procedure are also characterized as a function of pre-strain, dye concentration, and crosslink density. Results show monodomain (highly ordered liquid crystal elastomer), low dye concentration, and crosslinked liquid crystal elastomers have a larger photomechanical response than polydomain, high dye concentration (0.25%mol - 1%mol), non-crosslinked liquid crystal elastomers.
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Details
- Title
- Application-driven studies of photomechanical materials
- Creators
- Elizabeth Adeline Bernhardt
- Contributors
- Mark G Kuzyk (Advisor)Brian A Collins (Committee Member)Weihong Zhong (Committee Member)Fred Gittes (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Department of Physics and Astronomy
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Number of pages
- 221
- Identifiers
- 99900581822801842
- Language
- English
- Resource Type
- Dissertation