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Molecular brushes of poly(2-oxazoline)s [Elektronische Ressource] / Ning Zhang


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Published 01 January 2010
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Wacker-Lehrstuhl fü r Makromolekulare Chemie

Molecular Brushes of Poly(2-oxazoline)s

Ning Zhang

Vollstä ndiger Abdruck der von der Fakultä t fü r Chemie der Technischen Universitä t
Mü nchen zur Erlangung des akademischen Grades eines

Doktors der Naturwissenschaften

genehmigten Dissertation.

Vorsitzender: Univ.- Prof. Dr. Ulrich K. Heiz
Prü fer der Dissertation: 1. Univ.- Prof. Dr. Rainer Jordan, Technische Universitä t Dresden
2. Univ.- Prof. Dr. Sevil Weinkauf

Die Dissertation wurde am 24.08.2010 bei der Technischen Universitä t Mü nchen eingereicht
und durch die Fakultä t fü r Chemie am 19.10.2010 angenommen Die vorliegende Arbeit wurde in der Zeit von November 2006 bis Mä rz 2010 unter der
Leitung von Prof. Dr. Rainer Jordan am Wacker-Lehrstuhl fü r Makromolekulare Chemie von
Prof. Dr. Dr. h.c. Bernhard Rieger der Technischen Universitä t Mü nchen angefertigt.


First and foremost, I would like to gratefully and sincerely thank my supervisor, Prof. Dr.
Rainer Jordan, for giving me the opportunity to work on such an exciting project. He
introduced me to the field of polymer and interface science, broadened my perspective and
knowledge, and gave me confidence to apply myself in my graduate study. I am deeply
impressed by his wide knowledge, patient guidance as well as the professional attitude
towards scientific work. When I made the decision to stay in Munich for the last few months
of my Ph.D. study, he also showed his kind understanding of it which has been of great
importance to me. Without his constant support, guidance and encouragement this dissertation
would not have been possible.
I would also like to express my deep gratitude to Prof. Dr. Dr. h. c. Bernhard Rieger for
giving me the opportunity to work at the Wacker-Lehrstuhl fü r Makromolekulare Chemie.
His constructive comments and scientific work style continually impressed me and have been
of great value for my work. I wish to sincerely thank Prof. Dr. -Ing. Oskar Nuyken, whose
generous supports and encouragement always inspired me and became a large driving force
for the present study. I gratefully thank Dr. Carsten Troll and Dr. -Ing. Heidi Samarian for
their supports both technically and scientifically.
A warm and heartfelt thank goes to Dr. Marin Steenackers and Dr. Robert Luxenhofer for
their fruitful cooperation, enlightening discussion and most importantly their warm friendship
throughout my Ph.D. study. Marin taught me the valuable laboratory techniques, and put time
and energy into correcting this dissertation. „Luxi‟ always helped me with suggestion on both
my work and my life, and offered me the “warmest hotel” in Dresden. Words are not
sufficient enough to express all my appreciation for their countless help.
I am grateful to Dr. Tilo Pompe from Leibniz Institute of Polymer Research Dresden for
performing the protein adsorption and cell adhesion experiments, and Dr. Schilp Sö ren from
Universitä t Heidelberg for offering the surfaces. Without these excellent cooperations, this
dissertation would not have been completed.
Many thanks to Naï ma Aurelia Hutter for her precise English-German translation, as well as
her kind help during my graduate study. At the same time, I would like to thank Anita Schulz
and Hans Koss for their kind assistance in the lab work.
I would like to give my special thank to my labmates Dr. Stephan Huber, Dr. Tianzhu Zhang,
Amir Doroodian, and Khalifah Salmeia for the harmonious lab atmosphere.
Thanks go to all the other Makros, Dr. Martin Schneider, Andreas Feigl, Dr. Liyi Chen,
Gerhard Richter, Dr. Carola Gantner, Ulrike Will, Dr. Michael Reif, Dr. Sergei Vagin, Uwe
Seemann, Alexander Schö bel, Timo Korfmann, Udo Schmidt, Paul Heinz, Monika Kellner,
Anastasia Golosova, Sabine Martinetz-Groß e, Timo Anselment, Pierre Gö ppert, Dr. Julia
Mü ller, Felix Schulz, Frank Deubel, Stephan Klaus, Christian Hanisch, Joachim Dengler, Dr.
Carly Anderson, Manuel Winkenstette, Philip Zehetmaier, Sanna Zimmer, Sandra
Hochwarter, Robert Reichardt, Maximilian Lehenmeier, Konrad Hindelang, Meifang Yin,
Tobias Diesner, Abdussalam Qaroush, Manfred Gunesch, Anna Lennartson, as well as other
new comers for making my stay such a pleasant and great experience. I sincerely appreciate
all the advices and skills that I have picked up in this period of time.
I would like to thank my parents and my friends for their love and help.
Finally, I would like to give my last but unique thank to my wife Hang for her endless love,
termless sacrifice and patience.

To my wife Hang

Table of Contents

1. Introduction· ······································1
1.1 Molecular brushes··········································································2
1.1.1 Synthesis of molecular brushes·························3
1.1.2 Stimuli-responsive molecular brushes·····················8 Stimuli-responsive polymers·········································8 Thermo-responsive molecular brushes···············9
1.1.3 Molecular brushes on surfaces·························12
1.2 Polymer Brushes··········································································14
1.2.1 Self-initiated photografting and photopolymerization (SIPGP)·· ·····17
1.2.2 Bottle-brush brushes (BBBs)··························20
1.3 Bioactive surfaces······································································· 21
1.4 Poly(2-oxazoline)s········ ···· ···· ·· ····························24
1.4.1 2-Oxazoline····································24
1.4.2 Living cationic ring-opening polymerization (LCROP) ··········24
1.4.3 Thermo-responsive poly(2-oxazoline)s·······································27
1.4.4 Biomedical applications of poly(2-oxazoline)s···············28

2. Objective of this work·· ············ ····· ········ ····· ········ ····· ········ ····· ···· 30

3. Results and discussion··· ······························31
3.1 Monomer synthesis········································································31
3.2 Molecular brushes via free radical and cationic polymerization of
2-oxazolines························· ··············· ··············· ··············· ··········· 33
3.2.1 Reaction of 2-isopropenyl-2-oxazoline·······································33
3.2.2 Polymerizations·································34
3.2.3 Thermo-responsiveness of poly(2-oxazoline)s molecular brushes····42
3.2.4 Morphology of adsorbed molecular brushes on surfaces··········45
3.2.5 Cytotoxicity assay, MTT····························47
3.3 Molecular brushes via anionic and cationic ring-opening polymerization···· 49
3.3.1 Anionic polymerization of 2-isopropenyl-2-oxazoline········ ·· ···49
3.3.2 Kinetic studies of the living cationic ring-opening polymerization of
2-oxazolines········· ····· ················································· ·······52
3.3.3 Thermo-responsive properties - impact of different parameters on the
LCST······································· ··· 58 Side chain length effect··············································58 Concentration effect·························64 Backbone length effect························65
3.4 Molecular brushes with copoly(2-oxazoline)s side chains·············· 68
3.4.1 Background····································68
3.4.2 Molecular brushes with statistical copolymer side chains·········68 Synthesis································69 LCST of molecular brushes with random copolymer side chains
3.4.3 Molecular brushes with block copolymer side chains···········73 LCST of molecular brushes with block copolymer side chains
3.5 Bottle-brush brushes of poly(2-oxazoline)s·····················76
3.5.1 Background·······································································76
3.5.2 Bottle-brush brushes of poly(2-oxazoline)s on glassy carbon······77 Glassy carbon·····························77 Self-initiated photografting and photopolymerization······78 Surface-initiated living cationic ring-opening polymerization·82