Controlled nanostructures of synthetic and biological polymers investigated by scanning force microscopy techniques [Elektronische Ressource] / von Wei Zhuang

Zhuang Han, Jiao Wei

Sujets

• Physik

Informations

• Publié par: humboldt-universitat_zu_berlin
• Publié le: 01 janvier 2009
• Nombre de lectures: 19
• Langue: English
• Poids de l'ouvrage: 13 Mo

Extrait

Controlled nanostructures of synthetic and
biological polymers investigated by
scanning force microscopy techniques

D I S S E R T A T I O N
zur Erlangung des akademischen Grades
Doctor rerum naturalium
(Dr. rer. nat.)
im Fach Chemie
eingereicht an der
Mathematisch-Naturwissenschaftlichen Fakultät I
Humboldt-Universität zu Berlin

von
Herr Wei Zhuang (M. Sc.)
geboren am 19.04.1977 in Shanghai, China
Präsident der Humboldt-Universität zu Berlin:
Prof. Dr. Dr. h. c. Christoph Markschies
Dekan der Mathematisch-Naturwissenschaftlichen Fakultät I:
Prof. Dr. Lutz-Helmut Schön
Gutacher/Gutachterin:
1. Prof. Dr. Jürgen P. Rabe
2. Prof. Dr. Klaus Rademann
3. Prof. Dr. Paolo Samorì
eingereicht am: 06.11.2009
Tag der mündlichen Prüfung : 20.11.2009
Abstract
Polymeric nanostructures from highly attractive, functional synthetic and biological
macromolecules were self-assembled at interfaces and in thin films, and then explored with
Scanning Force Microscopy (SFM) techniques, in order to develop a molecular level
understanding, which allows to control their properties.
A widely used polymer for organic electronics, poly(3-hexylthiophene) (P3HT), was
investigated in thin films in order to determine the role of molecular weight for the formation
of molecular nanostructures, and the correlation with the corresponding transistor properties
and charge carrier mobilities. The correlation with the electrical and optical properties
indicates that the electronic properties are largely determined by the backbone conformation
of the majority of the polymer chains rather than due to the previously suspected effect of the
grain boundaries associated with the polycrystallinity of the material.
On the level of single macromolecules, dendronized polymers, a rather novel class of
macromolecules, were investigated. For the first time, self-folding of single synthetic
polymer chains into polymeric duplexes was reported. Moreover, it became possible to
detect rare single polymer topologies, such as chain branching, which could not be detected
by any other means so far.
The complexation of plasmid double-stranded DNA (ds-DNA) with amphiphilic small
molecules allowed to control the macromolecular conformation with a “Molecular
Workbench”, developed largely within this thesis. It became possible to split, stretch,
overstretch, and finally break ds-DNA on molecularly modified graphite surfaces. With a
newly developed “SFM blowing” technique, supercoiled ds-DNA and also synthetic block
copolymers from DNA and poly(ethyleneglycol) were fully stretched on an atomically flat
substrate. Quantitative experiments allowed to estimate rupture forces of ds-DNA on a time
scale on the order of as much as half an hour.
In summary, this work presents new insight into highly interesting functional polymeric
nanostructures as well as new methods for their investigation. The results are relevant for a
development of biologically inspired functional molecular systems, which may ultimately
operate close to physical limits as far as the efficiency of matter and energy is concerned.
Keyword: SFM, manipulation, polymer, DNA, nanostructure, single molecule, AFM
Zusammenfassung
Polymere Nanostrukturen aus interessanten, funktionalen synthetischen und biologischen
Makromolekülen wurden an Grenzflächen und in dünnen Filmen selbstorganisiert, und
dann mit Hilfe von Rasterkraftmikroskopie (SFM) - Techniken erforscht, um ein
Verständnis auf molekularer Ebene zu entwickeln, das es erlaubt, ihre Eigenschaften
kontrolliert einzustellen.
Eine weit verbreitetes Polymer für die organische Elektronik, Poly(3-hexylthiophen)
(P3HT), wurde in dünnen Filmen untersucht, um den Einfluß des Molekulargewichts auf
die Ausbildung molekularer Nanostrukturen und die Korrelation mit den entsprechenden
Transistor Eigenschaften und Ladungsträger-Beweglichkeiten zu bestimmen. Die
Korrelation mit den elektrischen und optischen Eigenschaften weisen darauf hin, dass die
elektronischen Eigenschaften wesentlich von der Rückgratskonformation der Mehrheit der
Polymerketten bestimmt werden, und weniger - wie bisher vermutet - von den
Korngrenzen des polykristallinen Materials.
Auf der Ebene einzelner Makromolekülen wurden dendronisierte Polymere, eine relativ
neue Klasse von Makromolekülen, untersucht. Zum ersten Mal wurde über die spontane
Faltung einzelner synthetischer Polymerketten berichtet. Darüber hinaus ist es gelungen,
seltene einzelne Polymertopologien wie z.B. Kettenverzweigung nachzuweisen, die nicht
durch andere Methode nachweisbar sind.
Die Komplexierung von doppelsträngiger-DNA (ds-DNA) mit amphiphilen kleinen
Molekülen erlaubt es, makromolekulare Konformationen durch eine "Molekulare
Werkbank" zu kontrollieren, die wesentlich in der vorliegenden Arbeit entwickelt wurde.
Damit wurde es möglich, ds-DNA auf molekular modifizierten Graphit-Oberflächen zu
spalten, auszustrecken, zu überdehnen, und schließlich zu brechen. Mit einer neu
entwickelten "SFM Blowing"-Technik wurden überdrillte („supercoiled“) ds-DNA und
synthetische Block-Copolymere aus DNA und Poly(ethylenglycol) vollständig auf einem
atomar flachen Substrat ausgestreckt. Auf der Basis quantitativer Experimente konnte die
Reißkraft für ds-DNA auf einer Zeitskala bis zu einer halben Stunde bestimmt werden.
Insgesamt liefert die vorliegende Arbeit neue Einblicke in hoch interessante funktionale
polymere Nanostrukturen sowie neue Methoden für deren Untersuchung. Die Ergebnisse
sind von großer Bedeutung für die systematische Entwicklung von biologisch inspirierten,
funktionalen molekularen Systemen, die letztlich nahe an physikalischen Grenzen
operieren, etwa was die effiziente Nutzung von Materie und Energie angeht.
Schlagworte: Rasterkraftmikroskopie, Manipulation, Polymere, DNA, Nanostruktur,
einzelne Moleküle.
Acknowledgements
First and foremost I would like to thank Prof. Dr. Jürgen P. Rabe, who offered me the
challenging projects and always generously provides me his patient education and
invaluable advice, so I could learn so much not only about science but also life in general.
His PMM group offers me a comfort, yet stimulating supporting network. In particular, Dr.
Nikolai Severin always patiently gives me the scientific guidance and kindly shares his
broad experiences and deep understanding ranging from DNA, SFM, science frictions to
Karate Arts…
During my PhD studies, I have collaborated with several research groups; therefore, I want
to offer my sincere appreciation to Prof. Dr. A. Dieter Schlüter and his group in ETH Zürich,
especially to Dr. Edis Kasëmi, who provided me the excellent synthetic dendronized
polymers involved in the thesis. I would like to thank Dr. Achmad Zen and Prof. Dieter
Neher at University of Potsdam for the collaboration in P3HT thin film experiment, Dr. Fikri
E. Alemdaroglu and Dr. Andreas Herrmann at the Max Planck Institute for Polymer
Research in Mainz for collaboration in DNA-PEG copolymer, Prof. Igor Sokolov at
Humboldt University for collaboration in working out the mechanism of blowing effect, Dr.
Ken Woycechowsky and Prof. Donald Hilvert for collaboration in encapsulated engineering
proteins.
I would also express my thanks to all ex- and current-members of PMM group, in particular
to Hua Liang and Manuel Gensler for many exciting experiments and discussions we
enjoyed together, to Jörg Barner for teaching me SFM manipulation through his powerful
equipment, to PD Dr. Stefan Kirstein and Dr. Norbert Koch for their helps and the fruitful
discussions, to Jörn-Oliver Vogel, Rolf Kniprath, Omar Al-Khatib and Stefan Eilers for the
friendly and enjoyable time we experience together. Necessarily to keep in mind Lothar
Geyer for his instantaneous help regarding all computer problems and Evi Poblenz for her
technical support in labs. Sincere thanks also extend to Sabine Schönherr and Dörthe M.
Eisele, who make PMM group and Sfb 448 running smoothly.
For the financial support, I gratefully acknowledge the German Science Foundation
(Deutsche Forschungsgemeinschaft) under Sfb 448 Mesoskopisch strukturierte
Verbundsysteme.
Last but not least, I would like to thank my family for their continuous support and
inspiration. There is no way to fully express my gratefulness to my lovely wife Min and our
precious son Aichen for their continuous love, support and enjoyable time.
Abbreviations
AFM Atomic force microscopy
ALS Aquifex aeolicus lumazine synthase
BP or bp Base pairs
b.p. Boiling point
C TAB Trimethylhexadecyl- ammonium bromide 16
CMC Critical micelle concentration
DA Dodecylamine (C H NH ) 12 25 2
Denpol Dendronized polymer
DP Degree of polymerization
DPN Dip-Pen Nanolithograpy
DSC Differential Scanning Calorimetry
FJC Free joint chain
G4PMMA 4th generation dendronized PMMA
GPC Gel Permission Chromatography
HOPG Highly Oriented Pyrolytic Graphite
JC Janus Chain
MW Molecular Weight
MWD Molecular weight distrib