Bowling Green State University
Kulawardana, Erandimala Udamini.
Degree: PhD, Photochemical Sciences, 2010, Bowling Green State University
Stimuli-responsive polymers are of both
fundamental and commercial interest. Such polymers respond
dramatically to external stimuli such as changes in light, pH,
temperature, mechanical force, electric field, or solvent
composition. Hydrogels and organogels that can respond to external
stimuli by changing their microstructures from collapsed to
expanded as well as by reversibly returning to their initial state
with or without the stimuli are important. Herein, three
stimuli-responsive polymers have been explored. They are
Photoresponsive oil sorbers, Photo- and thermo- responsive
hydrogels, and photo- and electro- responsive hydrogels.
A photoresponsive oil sorber with a hydrophobic,
photoresponsive core and shell has been synthesized via suspension
polymerization. Lauryl acrylate (LA), isodecyl acrylate (IDA) and
tert-butylstyrene (tBS) were used as monomers,
4-(methacrylamino)azobenzene (Azo-M) was used as a photoresponsive
monomer, and bis(methacryloylamino)azobenzene (Azo-CL-M) was
employed as a photoresponsive surface cross-linker. The oil sorber
prefers non-polar solvents. It absorbed 15 times its dry weight in
toluene, 19 times its dry weight in chloroform and 16 times its dry
weight in dichloromethane. Rapid and photoresponsive desorption of
solvent (86% of solvent expulsed in 30 minutes) was characteristic.
The new oil sorber is an excellent gasoline absorber rapidly
increasing its body weight in its presence. And also, it is less
dense than water, and can potentially be utilized for cleaning oil
spills on water. A dual-stimuli responsive
hydrogel with a thermoresponsive backbone and photochromic pendant
groups was synthesized via free radical polymerization using
N-isopropylacrylamide (NIPAAm) as main monomer,
(MSp) (MSp) as photochromic monomer, the crosslinker
N,N'-methylenebisacrylamide (BIS) and the initiator
2,2'-azobisisobutyronitrile (AIBN) in dimethylsulfoxide (DMSO). The
polymers are dual responsive, in that poly(N-isopropylacrylamide)
[PNIPAAm] responds to temperature changes while the pendant
spironaphthoxazines respond to light. Irradiation enhanced the
water absorption of the polymers while increases in temperature
decreased it. The irradiated PNIPAAm-MSp showed best water
absorption at 0 °C (Q = 3.25) while water desorbed at higher
temperatures (35 °C; Q = 0.30); where Q is the amount of water
absorbed by a gram of dry polymer.
Photoresponsive bending of rod shaped
PNIPAAM-MSp hydrogels under a DC electric field have been
investigated. The excited state formed by the absorption of light
dissociated at the spiro C-O bond of the spironaphthoxazine moeity
and generated charges in the polymer. These then aligned with the
electric field to cause bending of the polymer. In the absence of
light, the bent polymers reversibly straightened. The
photoresponsive bending became faster in salt solutions and the
direction of bending switched with the changing polarity of the
electric field. No…
Advisors/Committee Members: Neckers, Douglas (Advisor).
Subjects/Keywords: Polymers; Stimuli-responsive polymers; Photoresponsive; Oil Sorbers; Hydrogels; Thermoresponsive; Electro-responsive
to Zotero / EndNote / Reference
APA (6th Edition):
Kulawardana, E. U. (2010). Stimuli-Responsive Polymers. (Doctoral Dissertation). Bowling Green State University. Retrieved from http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1280669888
Chicago Manual of Style (16th Edition):
Kulawardana, Erandimala Udamini. “Stimuli-Responsive Polymers.” 2010. Doctoral Dissertation, Bowling Green State University. Accessed December 05, 2019.
MLA Handbook (7th Edition):
Kulawardana, Erandimala Udamini. “Stimuli-Responsive Polymers.” 2010. Web. 05 Dec 2019.
Kulawardana EU. Stimuli-Responsive Polymers. [Internet] [Doctoral dissertation]. Bowling Green State University; 2010. [cited 2019 Dec 05].
Available from: http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1280669888.
Council of Science Editors:
Kulawardana EU. Stimuli-Responsive Polymers. [Doctoral Dissertation]. Bowling Green State University; 2010. Available from: http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1280669888