Dissertation
Spectroscopic investigations of inhomogeneous barrier mechanisms of reversible photodegradation of aminoanthraquinone-doped polymer matrices
Doctor of Philosophy (PhD), Washington State University
01/2015
Handle:
https://hdl.handle.net/2376/111332
Abstract
Reversible photodegradation is a relatively new phenomenon observed
mostly in dye-doped polymer materials. While the mechanism responsible
for reversible photodegradation is not yet understood, a kinetic model
describing the time-dependence of reversible photodegradation has
been quantitatively examined with previous studies in disperse orange
11 doped in poly(methyl methacrylate) (DO11/PMMA) using amplified
spontaneous emission (ASE) and transmittance image microscopy (TIM)
techniques. However, we find that the latest kinetic model is inconsistent
with new experimental results.
We hypothesize a mechanism responsible for reversible photodegradation
of 1-substituted aminonanthraquinones doped in two polymers, PMMA
and polystyrene. In this hypothesis, photodegradation of dye originates
from (photo)chemical reactions between dye and thermally-degraded
polymers, and recovery corresponds to the metastable reaction products
returning back to the pristine dye. Reversible photodegradation of
dye dissolved in liquid monomers and doped in polymers have been studied
using ultraviolet-visible (UV-Vis) spectroscopy. The absorption spectra
of proposed photodegraded species are obtained experimentally and
compared with time-dependent density functional theory calculations.
The change of molecular structures in reversible photodegradation
is investigated with Fourier transform infrared spectroscopy. These
results qualitatively verify the proposed mechanism.
New experimental results suggest inhomogeneous kinetics of photodegradation
and recovery, and diffusion is proved to not be involved. Reversible
photodegradation experiments probed with ASE and UV-Vis spectroscopy
simultaneously confirm that new observations are the same processes
as in previous studies probed with ASE. Comparing new results of photodegradation
in DO11/PMMA with previous ASE studies, we find that the photodegradation
rate may vary depending on whether the irradiation generates ASE,
which results in disagreement between two studies. We also find that
the temperature dependent photodegradation and recovery data supports
an energy barrier scenario which contradicts the previous model, but
does not fully agree with a simple energy barrier model. A possible
cause is that the correct rate distribution due to special heterogeneity
is not yet found.
The proposed mechanism indicates that a key to improve the photo-stability
of doped polymers is to eliminate the possibility of (photo)chemical
reactions occurring between dopants and thermally-degraded polymers.
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Details
- Title
- Spectroscopic investigations of inhomogeneous barrier mechanisms of reversible photodegradation of aminoanthraquinone-doped polymer matrices
- Creators
- Sheng-Ting Hung
- Contributors
- Koen Clays (Advisor)Mark G Kuzyk (Advisor)Brian A Collins (Committee Member)Guy Koeckelberghs (Committee Member)Matthew D McCluskey (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Physics and Astronomy, Department of
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Number of pages
- 213
- Identifiers
- 99900581839501842
- Language
- English
- Resource Type
- Dissertation