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University of Kentucky Doctoral Dissertations Graduate School
2007
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Sumod Kalakkunnath
University of Kentucky, [email protected]
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Kalakkunnath, Sumod, "VISCOELASTIC RELAXATION CHARACTERISTICS OF RUBBERY POLYMER
NETWORKS AND ENGINEERING POLYESTERS" (2007). University of Kentucky Doctoral Dissertations. 486.
https://uknowledge.uky.edu/gradschool_diss/486
This Dissertation is brought to you for free and open access by the Graduate School at UKnowledge. It has been
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ABSTRACT OF DISSERTATION
Sumod Kalakkunnath
The Graduate School
University of Kentucky
2007
VISCOELASTIC RELAXATION CHARACTERISTICS OF RUBBERY POLYMER
NETWORKS AND ENGINEERING POLYESTERS
ABSTRACT OF DISSERTATION
A dissertation submitted in partial fulfillment of the
requirements for the degree of Doctor of Philosophy in the
College of Engineering
at the University of Kentucky
By
Sumod Kalakkunnath
Lexington, Kentucky
Director: Dr. Douglass S. Kalika, Associate Professor of Chemical Engineering
Lexington, Kentucky
2007
Copyright © Sumod Kalakkunnath 2007
ABSTRACT OF DISSERTATION
VISCOELASTIC RELAXATION CHARACTERISTICS OF RUBBERY POLYMER
NETWORKS AND ENGINEERING POLYESTERS
The relaxation characteristics of rubbery poly(ethylene oxide) [PEO] networks have been
investigated as a function of network composition and architecture via dynamic
mechanical analysis and broadband dielectric spectroscopy. A series of model networks
were prepared via UV photopolymerization using poly(ethylene glycol) diacrylate
[PEGDA] as crosslinker: variations in crosslink density were achieved either by the
introduction of water in the prepolymerization reaction mixture, or by the inclusion of
mono-functional acrylate such as poly(ethylene glycol) methyl ether acrylate [PEGMEA]
or poly(ethylene glycol) acrylate [PEGA]. Copolymerization with mono-functional
acrylate led to the insertion of flexible branches along the network backbone, and the
corresponding glass-rubber relaxation properties of the copolymers (i.e., T , relaxation
g
breadth, fragility) were a sensitive function of network architecture and corresponding
fractional free volume. Relatively subtle variations in network structure led to significant
differences in relaxation characteristics, and a systematic series of studies was undertaken
to examine the influence of branch length, branch end-group, and crosslinker flexibility
on viscoelastic response. Dielectric spectroscopy was especially useful for the elucidation
of localized, sub-glass relaxations in the polymer networks: the imposition of local
constraint in the vicinity of the crosslink junctions led to the detection of a distinctive
“fast” relaxation process in the networks that was similar to a comparable sub-glass
relaxation observed in crystalline PEO and in the confined regions of PEO
nanocomposites. Gas permeation studies on the model PEGDA networks confirmed their
utility as highly-permeable, reverse-selective membrane materials, and strategic control
of the network architecture could be used to optimize gas separation performance.
Dynamic mechanical and dielectric measurements have also been performed on a
semicrystalline polyester, poly(trimethylene terephthalate) [PTT], in order to assess the
influence of processing history on the resultant morphology and corresponding
viscoelastic relaxation characteristics. Studies on both quenched and annealed PTT
revealed the presence of a substantial fraction of rigid amorphous phase (RAP) material
in the crystalline samples: dielectric measurements showed a strong increase in relaxation
intensity above the glass transition indicating a progressive mobilization of the rigid
amorphous phase with increasing temperature prior to crystalline melting.
KEYWORDS: dynamic mechanical analysis, broadband dielectric spectroscopy, UV
photopolymerization, poly(ethylene oxide), poly(trimethylene terephthalate).
Sumod Kalakkunnath
o 03/12/2007 o
VISCOELASTIC RELAXATION CHARACTERISTICS OF RUBBERY POLYMER
NETWORKS AND ENGINEERING POLYESTERS
By
Sumod Kalakkunnath
Dr. Douglass S. Kalika o
Director of Dissertation
Dr. Barbara Knutson o
Director of Graduate Studies
03/12/2007 p
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DISSERTATION
Sumod Kalakkunnath
The Graduate School
University of Kentucky
2007
VISCOELASTIC RELAXATION CHARACTERISTICS OF RUBBERY POLYMER
NETWORKS AND ENGINEERING POLYESTERS
DISSERTATION
A dissertation submitted in partial fulfillment of the
requirements for the degree of Doctor of Philosophy in the
College of Engineering
at the University of Kentucky
By
Sumod Kalakkunnath
Lexington, Kentucky
Director: Dr. Douglass S. Kalika, Associate Professor of Chemical Engineering
Lexington, Kentucky
2007
Copyright © Sumod Kalakkunnath 2007
ACKNOWLEDGEMENTS
First and foremost, warmest regards to my advisor, Dr. Douglass S. Kalika, without
whom this work would have been impossible. A very genuine person at heart, Dr. Kalika
has been a constant source of inspiration and assurance. He has helped me flourish not
only as a researcher but also as a person, through his exemplary dedication towards both
work and family. It has been an interesting and ongoing challenge to achieve his sense of
perfection. I will always cherish the intellectually stimulating research meetings which
were usually followed by lighter notes on music, sports and current affairs. In short,
working with him over these years has been an enriching experience.
I would also like to thank, Dr. Benny Freeman (University of Texas at Austin) for
providing the outstanding opportunity to collaborate with him. This joint effort has added
a new dimension to my research and improved the quality of my work substantially.
Special thanks to his team (Haiqing, Scott and Roy) for their assistance and input
throughout the project.
The time spent here in Lexington has been memorable; thanks to all my friends. The road
trips, get-togethers, coffee breaks and luncheon sessions will be forever etched in my
mind. My dearest friends, Amita and Vivek, and my cousins, Sreeja and Manoj, deserve a
special mention for being unwavering in their support.
Finally, I dedicate this work to my parents, Leela and Sethu, who will always remain a
part of me. The values instilled by them will continue to help me strive to accomplish
future goals.
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Description:A series of model networks were prepared via UV photopolymerization using poly(ethylene glycol) diacrylate mono-functional acrylate such as poly(ethylene glycol) methyl ether acrylate [PEGMEA] or poly(ethylene . My dearest friends, Amita and Vivek, and my cousins, Sreeja and Manoj, deserve a.
