Reactive amphiphilic block copolymers for the preparation of hybrid inorganic, organic materials [Elektronische Ressource] / Melanie Siebert

Informations

• Publié par: rheinisch-westfalischen_technischen_hochschule_-rwth-_aachen
• Publié le: 01 janvier 2011
• Nombre de lectures: 16
• Langue: English
• Poids de l'ouvrage: 4 Mo

Extrait

Reactive Amphiphilic Block Copolymers
for the Preparation of
Hybrid Inorganic/Organic Materials



Von der Fakultät für Mathematik, Informatik und Naturwissenschaften
der RWTH Aachen University zur Erlangung des akademischen Grades
einer Doktorin der Naturwissenschaften genehmigte Dissertation

vorgelegt von

Diplom-Biochemikerin
Melanie Siebert
aus Hannover



Berichter:
Universitätsprof. Dr. rer. nat. Martin Möller
Universitätsprof. Dr. rer. nat. Walter Richtering


Tag der mündlichen Prüfung: 12. September 2011


Diese Dissertation ist auf den Internetseiten der Hochschulbibliothek online verfügbar.










































Table of contents

List of Abbreviations v

Summary ix

Zusammenfassung xi

Chapter 1 Introduction 1

Chapter 2 Starting materials, procedures and methods
for the preparation and characterisation of
metallic nanoparticles – A short overview 5

Synthesis of well-defined PS-b-PG block Chapter 3
copolymers by anionic polymerisation 29

Chapter 4 Micelle formation in organic solvents 55

Chapter 5 Preparation of hybrid inorganic/organic
materials 73

Chapter 6 Thin TiO films on silicon wafer 97 2

Acknowledgement 107

List of Publications 109


Curriculum Vitae 110










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iv


List of Abbreviations

A second virial coefficient 2
ACF autocorrelation function
AFM atomic force microscopy
Ar aromatic proton(s)
BHT 2,6-di-tert-butyl-4-methylphenole
Bu Mg dibutylmagnesium 2
CaH calcium hydride 2
calc. calculated
CDCl deuterated chloroform 3
cmc critical micelle concentration
conc. concentrated
δ chemical shift
d day(s)
D diffusion coefficient
DLS dynamic light scattering
DMAc N,N-dimethylacetamide
DMF N,N-dimethylformamide
DMSO-d deuterated dimethylsulfoxide 6
dn/dc refractive index increment
DSC differential scanning calorimetry
EEGE ethoxy ethyl glycidyl ether
EELS electron energy loss spectroscopy
EFTEM energy filter transmission electron microscopy
eq equivalent(s)
FESEM field emission gun scanning electron microscopy
2
g (t) intensity fluctuation
GPC gel permeation chromatography
h hour(s)
h height
HPLC high-pressure liquid chromatography


v

HVL high vacuum line
I integral
I scattered intensity
[I] initiator concentration
KOtBu potassium tert-butoxide
λ wavelength
LAH lithium aluminium(III) hydride
LLS laser light scattering
[M] monomer concentration
max. maximum
MeOH methanol
min minute(s)
M number-average molecular weight n
M weight-average molecular weight w
N aggregation number agg.
NMR nuclear magnetic resonance
P periodicity
P -t-Bu phosphazene base or 1-tert-butyl-4,4,4-tris(dimethylamino)-4
2,2-bis-[tris(dimethylamino)-phosphoranylidenamino]-
5 5
2λ ,4λ -catenadi (phosphazene)]
P2VP poly(2-vinyl pyridine)
p.a. pure for analysis
PDI polydispersity index
PEEGE poly(ethoxy ethyl glycidyl ether)
PEO poly(ethylene oxide)
PG polyglycidol
PMAA poly(methacrylic acid)
PMMA poly(methyl methacrylate)
ppm parts per million
PS polystyrene
PTFE poly(tetrafluoroethylene)
r radius
R z-average radius of gyration g


vi

R hydrodynamic radius h
RI refractive index
ROP ring-opening polymerization
rpm rotations per minute
RT room temperature
RuO ruthenium oxide 4
s-BuLi sec-butyl lithium
SAXS small angle x-ray scattering
SEC size exclusion chromatography
SEM scanning electron microscopy
SFM scanning force microscopy
SLS static light scattering
TEM transmission electron microscopy
T glass transition temperature g
TGA thermogravimetric analysis
THF tetrahydrofuran
TiO titanium dioxide 2
Ti(OR) titanium(IV) isopropoxide 4
TMS tetramethylsilane
UV ultra-violet
V average particle volume micelle
w week(s)
wt-% weight percent
χ weight fraction of polyglycidol PG
XPS x-ray photoelectron spectroscopy












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viii


Summary

In this thesis the synthesis of well-defined polystyrene-block-polyglycidol (PS-b-
PG) block copolymers, their micelle formation and the use of these micelles for
the preparation of hybrid inorganic/organic materials are described. The hybrid
materials are used for patterning of highly ordered TiO nanoparticles on a 2
silicon wafer.

The amphiphilic block copolymers were synthesized by sequential anionic
polymerisation of the corresponding monomers in benzene with the sec-butyl
lithium/phosphazene base initiating system to achieve well-defined polystyrene-
block-poly(ethoxy ethyl glycidyl ether) (PS-b-PEEGE) block copolymers. It was
shown that chain-transfer reactions during the polymerisation process limit the
molecular weight of the PEEGE block and tailing in the SEC traces indicated
the presence of PEEGE homopolymer. The removal of the protection group was
achieved with concentrated hydrochloric acid or an acidic ion exchange resin. In
both cases the deprotection was quantitative, but in case of the hydrochloric
acid the reaction conditions played a very important role; under optimal
conditions no degradation of the PEEGE block in the copolymer was observed.
The PG homopolymer inside the block copolymer was responsible for the tailing
in SEC and was removed by precipitation of the block copolymer in distilled
water. The glass transition temperatures of PS-b-PEEGE and PS-b-PG were
determined by DSC. It could be shown that the PS-b-PEEGE block copolymers
were completely miscible proven by only one glass transition temperature. In
contrast, the PS-b-PG block copolymers had two glass transition temperatures
showing their immiscibility.
The PS-b-PG block copolymers were used for the preparation of micellar
solutions in toluene as selective solvent. The micelles were characterized by
static and dynamic light scattering as well as small angle X-ray scattering. The
results of the light scattering experiments showed that copolymers containing a
mass fraction of PG block below 0.5 self-assembled into core-shell micelles,
while samples with higher PG content formed non-specifically aggregated


ix

particles. Their presence resulted most probably from multiple hydrogen bond
formation between PG units that could strongly restrict their complete
equilibration in solution. Additionally, the micellar solutions of PS-b-PG block
copolymers were coated onto mica as substrate. It could be shown by SFM and
TEM that the dried micelles had mostly a spherical shape.
The well-defined core-shell micelles of PS-b-PG were loaded with concentrated
hydrochloric acid and titanium(IV) isopropoxide (Ti(OR) ) which lead to 4
hydrolysis of the titanium alkoxide within the micellar core. It was proven that a
condensation reaction lead to a permanent connection between glycidol units
and the inorganic component. As a consequence, stable hybrid micelles were
obtained, which were coated onto a substrate to form a thin film and analyzed
again by SFM and TEM.
The cross-linked micelles were used for the highly controlled nanostructuring of
TiO on the surface. The titanium-loaded micellar solutions were coated onto a 2
silicon wafer to obtain thin films. These thin films were treated with hydrogen
plasma to remove the organic material and convert the titanium alkoxide to well-
defined TiO nanoparticles. The hexagonal ordering of TiO was proven by 2 2
microscopic techniques and X-ray photoelectron spectroscopy confirmed the
chemical nature of the particles.
















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