Photopolymerizations of multicomponent epoxide and acrylate/epoxide hybrid systems for ...

267 Pages·2015·8.74 MB·English

by  Ho Seop Eom

University of Iowa
Iowa Research Online
Theses and Dissertations
2011
Photopolymerizations of multicomponent epoxide
and acrylate/epoxide hybrid systems for controlled
kinetics and enhanced material properties
Ho Seop Eom
University of Iowa
Copyright 2011 HOSEOP EOM
This dissertation is available at Iowa Research Online: https://ir.uiowa.edu/etd/2488
Recommended Citation
Eom, Ho Seop. "Photopolymerizations of multicomponent epoxide and acrylate/epoxide hybrid systems for controlled kinetics and
enhanced material properties." PhD (Doctor of Philosophy) thesis, University of Iowa, 2011.
https://ir.uiowa.edu/etd/2488.https://doi.org/10.17077/etd.32oat7x6
Follow this and additional works at:https://ir.uiowa.edu/etd
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PHOTOPOLYMERIZATIONS OF MULTICOMPONENT EPOXIDE AND
ACRYLATE/EPOXIDE HYBRID SYSTEMS FOR CONTROLLED KINETICS AND
ENHANCED MATERIAL PROPERTIES
by
Ho Seop Eom
An Abstract
Of a thesis submitted in partial fulfillment
of the requirements for the Doctor of
Philosophy degree in Chemical and Biochemical Engineering
in the Graduate College of
The University of Iowa
May 2011
Thesis Supervisors: Professor Alec B. Scranton and
Associate Professor Julie L.P. Jessop
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ABSTRACT
Cationic photopolymerization of multifunctional epoxides is very useful for
efficient cure at room temperature and has been widely used in coatings and adhesives.
Despite excellent properties of the final cured polymers, cationic photopolymerizations of
epoxides have seen limited application due to slow reactions (relative to acrylates) and
brittleness associated with a highly crosslinked, rigid network. To address these issues,
two reaction systems were studied in this thesis: photoinitiated cationic
copolymerizations of a cycloaliphatic diepoxide with epoxidized elastomers and
acrylate/epoxide hybrid photopolymerizations. Oligomer/monomer structures, viscosity,
compositions, and photoinitiator system were hypothesized to play important roles in
controlling photopolymerizations of the epoxide-based mixtures. A fundamental
understanding of the interplay between these variables for the chosen systems will
provide comprehensive guidelines for the future development of photopolymerization
systems comparable to the epoxide-based mixtures in this research.
For diepoxide/oligomer mixtures, the observed overall enhancement in
polymerization rate and ultimate conversion of the cycloaliphatic diepoxide was
attributed to the activated monomer mechanism associated with hydroxyl terminal groups
in the epoxidized oligomers. This enhancement increased with increasing oligomer
content. The mixture viscosity influenced the initial reactivity of the diepoxide for
oligomer content above 50 wt.%. Real-time consumption of internal epoxides in the
oligomers was successfully determined using Raman spectroscopy. Initial reactivity and
ultimate conversion of the internal epoxides decreased with increasing the diepoxide
content. This trend was more pronounced for the oligomer containing low internal
epoxide content. These results indicate that the reactivity of the hydroxyl groups is higher
toward cationic active centers of the diepoxide than those of the internal epoxides in the
oligomers. These conclusions are consistent with physical property results. The enhanced
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fracture toughness and impact resistance were attributed to multimodal network chain-
length distribution of copolymers containing the oligomer content between 70% and 80%.
For acrylate/epoxide hybrid mixtures, diacrylate oligomers significantly
suppressed reactivities of cycloaliphatic mono/diepoxides, which was attributed to high
mixture viscosity and highly crosslinked acrylate network. In this case, the dual
photoinitiator system did not favor the epoxide reaction. Depending on the monovinyl
acrylate secondary functionalities, enhanced reactivity and ultimate conversion of the
diepoxide were attributed to a combined effect of a reduced viscosity and the radical-
promoted cationic polymerization associated with the dual photoinitiator. The retarded
and inhibited diepoxide reactivities with ether and urethane secondary groups were
attributed to solvation and nucleophilicity/basicity effects, respectively. The influence of
the diepoxide on the acrylate reactivity was attributed to dilution and polarity effects. In
this case, high concentration of the free-radical photoinitiator is required for the dual
photoinitiator system. Physical properties of hybrid polymers also varied with acrylate
structures and monomer composition. Dynamic modulation methods were proposed to
enhance the diepoxide reactivity and final properties in the presence of urethane acrylates.
Abstract Approved: ____________________________________
Thesis Supervisor
____________________________________
Title and Department
____________________________________
Date
____________________________________
Thesis Supervisor
____________________________________
Title and Department
____________________________________
Date
PHOTOPOLYMERIZATIONS OF MULTICOMPONENT EPOXIDE AND
ACRYLATE/EPOXIDE HYBRID SYSTEMS FOR CONTROLLED KINETICS AND
ENHANCED MATERIAL PROPERTIES
by
Ho Seop Eom
A thesis submitted in partial fulfillment
of the requirements for the Doctor of
Philosophy degree in Chemical and Biochemical Engineering
in the Graduate College of
The University of Iowa
May 2011
Thesis Supervisors: Professor Alec B. Scranton and
Associate Professor Julie L.P. Jessop
Graduate College
The University of Iowa
Iowa City, Iowa
CERTIFICATE OF APPROVAL
_______________________
PH.D. THESIS
_______________
This is to certify that the Ph.D. thesis of
Ho Seop Eom
has been approved by the Examining Committee
for the thesis requirement for the Doctor of Philosophy
degree in Chemical and Biochemical Engineering at the May 2011 graduation.
Thesis Committee: ___________________________________
Alec B. Scranton, Thesis Supervisor
___________________________________
Julie L.P. Jessop, Thesis Supervisor
___________________________________
C. Allan Guymon
___________________________________
Joon B. Park
___________________________________
Chris N. Coretsopoulos
To my dearest family and parents, providing unconditional support and unchanging love

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ACKNOWLEDGEMENTS
First of all, I feel really thankful for this moment finalizing my Ph.D. thesis. To
me, life at Iowa was full of unknown news because there was a big transition in my major
from the Biomedical Engineering to the Chemical Engineering. When I switched my
major, it was a big decision and full of challenges because at that time my research
interests were all about biomaterials. Although I was not sure about the destination of my
Ph.D. journey at my gloomy days, I found new hopes and opportunities in
photopolymerization when I met Professor Alec Scranton and Professor Julie Jessop,
both my current academic advisors. Of course, it was not easy to change my research
interests in the beginning. However, with endless patience and encouragements Professor
Scranton and Professor Jessop have offered special opportunities for me to explore
different photopolymerization systems and contribute to such an exciting and cutting-
edge field of research through NSF and I/UCRC projects. The researches on several
topics allowed me to get feedbacks and learn flexible-thinking skills from several
companies such as 3M, DSM, Henkel, National Starch, and Cytec through
Industry/University Cooperative Research Center program. From the bottom of my heart
I really thank Professor Scranton and Professor Jessop for always inspiring me with
motivational comments throughout the years. When I look back on my Ph.D. journey, I
have earned more than Ph.D. degree from their true leadership as mentors and friends. I
was able to successfully travel this far because of their cooperative direction and found a
fantastic position in Micron Technology in Boise, Idaho.
I would like to say a special thanks to Professor Jun Park and Tae Hong Lim in
Biomedical Engineering Department for being mentors to me over the years. Especially, I
am very glad having Professor Jun Park in my research committee. I am the last student
receiving Ph.D. by him because he retired after having my individual Ph.D. defense with
him. Before switching my major, he was my hero and now he becomes my life mentor.
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His devotion in research and teaching will affect me throughout my life. In addition, I
would like to thank Professor Coretsopoulos and Professor Allan Guymon for their
supports and help. I will never forget the laughing sound of Professor Coretsopoulos as
well as nice conversations with him as a friend.
There are many other people without whom I have not successfully finished my
Ph.D. program in the Chemical and Biochemical Engineering Department. I would like to
thank Linda and Natalie for their professional assistance keeping me on track. I also
thank former (Leroy, Josh, Beth, Cindy, Dongkwan, Peter, Chris, Yuan, and so forth) and
current graduate students in our department who went through all difficulties together.
Friends! Our devotion to making a small step in all fields of engineering was never
worthless. Specially, I would like to give special thank Br. Soonki to help me decide my
career path between academia and industry.
Under the direction of my advisors, I was given many opportunities in mentoring
undergraduate students including Na Yeon Kang, Collette Black, James Kim, Sasha
Abdalla and cooperating with other graduate students. Such opportunities have profited
all of us: one of the students became a winner of the best poster award among
undergraduate students in a conference; research articles have been published.
I would like to give all the credits that I have earned during my whole Ph.D.
journey to my family. I really want to see my parents who have provided unconditional
support for a long time. My daughter and son motivate me to live my life as best as I can
every day. Finally, I give super special thanks to my loving wife, for sacrificing her
career as a teacher to support me, for understanding me more than anyone in any
occasions, for showing me unchanging love and trust with a sweet smile. Above all, I
really thank my Lord and God, Jesus for his exceeding mercy and love upon me and my
family. ―O give thanks unto the LORD; for he is good: because his mercy endureth for
ever‖ (Psalms 118:1). Praise the LORD!!
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TABLE OF CONTENTS

LIST OF TABLES ........................................................................................................... viii 
LIST OF FIGURES ........................................................................................................... ix  
CHAPTER 1 INTRODUCTION AND BACKGROUND ................................................1 
Introduction .......................................................................................................1 
Advantages of Photopolymerizations ........................................................1 
Cationic and Free-Radical Photopolymerizations .....................................2 
Importance of Modification of Neat Epoxide Photopolymerization
Systems ......................................................................................................3 
Background .......................................................................................................4 
Photoinitiation and Cationic photoinitiators ..............................................4 
Epoxide Monomers ...................................................................................9 
Propagation of Cationic Photopolymerizations .......................................11 
The Role of Water in Propagation ...........................................................13 
Acceleration of Cationic Photopolymerizations ......................................16 
Termination of Cationic Photopolymerization ........................................21 
Living Characteristic of Cationic Photopolymerization ..........................23 
Cationic Copolymerizations ....................................................................25 
Physical Properties of Cured Epoxides ...................................................27 
Toughening Mechanisms .........................................................................29 
Toughening Methods for Epoxide Thermosets .......................................31 
Hybrid Photopolymerizations ..................................................................35 
Notes ...............................................................................................................44 
CHAPTER 2 RESEARCH OBJECTIVES ......................................................................56 
Photoinitiated Cationic Copolymerization Systems .......................................57 
Hybrid Photopolymerization Systems ............................................................58 
CHAPTER 3 PHOTOINITIATED CATIONIC COPOLYMERIZATIONS
CONTAINING CYCLOALIPHATIC DIEPOXIDE AND
ELASTOMERIC OLIGOMERS: EFFECTS OF THE OLIGOMER
STRUCTURE AND COMPOSITION ......................................................60 
Introduction .....................................................................................................60 
Experimental ...................................................................................................62 
Materials ..................................................................................................62 
Characterization of Elastomeric Oligomers ............................................63 
Photoinitiator Photon Absorption Rate ...................................................64 
In-Situ Kinetic Study Using Real-time Measurements ...........................65 
Results and Discussion ...................................................................................67 
Characterization of Elastomeric Oligomers ............................................67 
Photoinitiator Photon Absorption Rate ...................................................70 
Cationic Photopolymerization of Neat Monomer and Oligomers ...........70 
Photoinitiated Cationic Copolymerization of EEC-EPOH Mixtures ......72 
Conclusions .....................................................................................................83 
Notes ...............................................................................................................84 
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