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From amphiphilic block copolymers to ferrocenyl-functionalized polymers for biosensoric applications [Elektronische Ressource] / Francisco Javier López Villanueva

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Published 01 January 2007
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“ FROM AMPHIPHILIC BLOCK COPOLYMERS
TO FERROCENYL-FUNCTIONALIZED POLYMERS
FOR BIOSENSORIC APPLICATIONS ”





Dissertation
zur
Erlangung des Grades

„ Doktor der Naturwissenschaften ”

am Fachbereich Chemie, Pharmazie und Geowissenschaften
der Johannes Gutenberg – Universität in Mainz







Francisco Javier López Villanueva


geboren in Rüsselsheim (Deutschland)


Mainz 2007


































Ein guter Ingenieur ist immer
ein bisschen konservativ …
zumindest auf dem Papier.

Scotty (in StarTrek – TNG)

ABSTRACT
The present thesis can be divided in three main parts. In all parts new polymer archi-
tectures were synthesized and characterized concerning their special features.
The first part will emphasize the advantage of a polystyrene-block-(hyperbranched
polyglycerol) copolymer in comparison to an analogue polystyrene-block-(linear poly-
glycerol) copolymer. Therefore a synthethic route to prepare linear block copolymers
has been developed. Two strategies were examined. One strategy was based on the
classic, sequential anionic polymerization; the second strategy was based on a
“Click-Chemistry” coupling reaction. In a following step glycidol was hypergrafted
from these block copolymers by applying a hypergrafting reaction with glycidol. The
behavior of the amphiphilic block copolymers synthesized was studied in different
solvents. Furthermore the polarity of the solvent was changed to form the corre-
sponding inverse micelles. DLS, SLS, SEC-MALLS-VISCO, AFM and Cyro TEM
measurements were performed to obtain a visual image from the appearance of the
aggregates. It was found that a linear-hyperbranched architecture is necessary, if
well defined, monodisperse aggregates are required, e.g. for the preparation of or-
dered nanoarrays. Linear-linear block copolymers formed only polydisperse aggre-
gates. Additionally it was found that size distribution could be improved dramatically
by passing the aggregates through a SEC column with large pores. The SEC col-
umns acted like a template in which the aggregates adopt a more stable conforma-
tion.
In the second part anionic polymerization was employed to synthesize silane-
endfunctionalized macromonomers with different molecular weights based on polybu-
tadiene and polyisoprene. These were polymerized by a hydrosilylation reaction in
bulk to obtain branched polymers, using Karstedt’s catalyst. Surprisingly the addition
of monofunctional silanes during the polymerization had only a minimal effect con-
cerning the degree of polymerization. It was possible to introduce silanes without in-
creasing the overall number of reaction steps by a very convenient “pseudo-copoly-
merization” method. All branched polymers were analyzed by SEC, SEC-MALLS,
1SEC-viscometry, H-NMR-spectroscopy and DSC concerning their branching ratio.
The branching parameters for the branched polymers exhibited similar characteristics
as hyperbranched polymers based on AB monomers. Detailed kinetic study showed 2
that the polymerization occurred very rapidly in comparison to the hydrosilylation po-
lymerization of classical AB type carbosilanes monomers. 2
The last part will deal with ferrocenyl-functionalized polymers. On the one hand,
ferrocenyl-functionalized polyglycerols (PG) were studied. Esterification of PGs with
different molecular weight using ferrocenemonocarboxylic acid gave the ferrocenyl
funtionalized polymers in high yields. On the other hand three different block copoly-
mers were prepared with different ratios of styrene to butadiene units (10:1, 4:1, 2:1).
The double bonds of the 1,2-PB block were hydrosilylated using silanes bearing one
(HSiMe Fc) or two (HSiMeFc ) ferrocene units. High degrees of functionalization 2 2
were obtained (up to 83 %). In this manner, six different ferrocenyl-rich block co-
polymers with different fractions of ferrocene were prepared and analyzed, employing
NMR-spectroscopy, SEC, SEC/MALLS/viscometry, DLS and cyclic voltammetry. The
redox properties of the studied polymers varied primarily with the nature of the silane
unit attached. Additionally, the redox properties in solution of the studied polymers
were influenced by the block length ratio of the block copolymers. Unexpectedly, with
increasing block length of the ferrocenyl block the fraction of active ferrocenes de-
creased. Nevertheless, in case of thin monolayer films this behaviour was not ob-
served. All polymers (PG and PS-b-PB based) exhibited good electrochemical prop-
erties in a wide range of solvents, which rendered them very interesting for biosen-
soric applications. TABLE OF CONTENTS

1. Introduction ............................................................................................................................ 7
1.1. Hyperbranched Polymers ................................................................................................ 7
1.1.1. Natural Origins......................................................................................................... 7
1.1.2. Mankind’s Answer ................................................................................................... 8
1.1.3. Degree of Branching .............................................................................................. 10
1.1.4. Contraction Factors 12
1.2. Synthetic Concepts........................................................................................................ 13
1.2.1. Inimer Concept....................................................................................................... 13
1.2.2. Slow Monomer Addition........................................................................................ 14
1.3. Block Copolymers 17
1.3.1. Structural Considerations ....................................................................................... 17
1.3.2. Linear-Dendritic Block Copolymers...................................................................... 19
1.3.3. Linear-Hyperbranched Block Copolymers ............................................................ 20
2. Objectives............................................................................................................................. 23
2.1. Introduction ................................................................................................................... 23
2.2. Particular Objectives ..................................................................................................... 25
2.2.1. Amphiphilic Block Copolymers – Synthesis ......................................................... 25
2.2.2. Amymers – Aggregation..................................................... 25
2.2.3. Branched Polydienes.............................................................................................. 26
2.2.4. Ferrocenyl Functionalized Polyglycerols............................................................... 27
2.2.5. Ferrocenyl Functionalized PS-block-PB Copolymers............................................ 27
3. Amphiphilic Block Copolymers – Synthesis ....................................................................... 29
3.1. Introduction..... 29
3.1.1. “Click-Chemistry”.................................................................................................. 29
3.2. Synthesis of Linear Block Copolymers......................................................................... 31
3.2.1. By Sequential Anionic Polymerization.................................................................. 31
3.2.2. “Click”-Coupling to AB-type Copolymers ............................................................ 35
3.2.3. “Click”-Coupling to ABA-type Copolymers ......................................................... 39
3.3. Hypergrafting of the linear block copolymers .............................................................. 41
3.4. Conclusion..................................................................................................................... 43
3.5. Experimental Part.......................................................................................................... 44
3.5.1. Materials................................................................................................................. 44
3.5.2. Synthesis of Styrene Homopolymers ..................................................................... 45
3.5.3. Synthesis of PEEGE Homopolymers 47
3.5.4. Synthesis of Block Copolymers ............................................................................. 48
4. Amphiphilic Block Copolymers – Aggregation................................................................... 50
4.1. Introduction ................................................................................................................... 50
4.1.1. Principles of Light Scattering................................................................................. 50
4.1.2. SEC with Triple Detection ..................................................................................... 54
4.2. Dynamic and Static Light Scattering Measurements .................................................... 57
4.2.1. Measurements in Chloroform 57
4.2.2. Measurements in Toluene ...................................................................................... 62
4.3. SEC Measurem ............................................................................... 66
4.4. Aggregate Structure in Nonpolar Solvents.................................................................... 73
4.5. Aggregation in Methanol .............................................................................................. 78
4.6. Conclusion..................................................................................................................... 82
5. Branched Polydienes............................................................................................................ 84
5.1. Introduction..... 84
5.1.1. Branched Polymers Based on Common Monomers .............................................. 84
5.1.2. Metal Catalyzed Hydrosilylation ........................................................................... 87
1TABLE OF CONTENTS
5.2. Synthesis and Properties of Branched Polyisoprenes ................................................... 89
5.3. Olefin Reactivity of Polyisoprenes ............................................................................... 95
5.4. Synthesis and Properties of Branched Polybutadienes ................................................. 96
5.5. Functionalized Polybutadienes Based on Common Silanes ....................................... 104
5.6. Functionalized Polyisoprenes Based on Common Silanes ......................................... 107
5.7. Ferrocenyl Functionalized Polydienes ........................................................................ 109
5.7.1. Functional Dienes based on the HSiMe Fc group ............................................... 109 2
5.7.2. Functional Dienes based on the HSiMeFc group 111 2
5.7.3. Electrochemistry of the Ferrocenyl Functionalized Polydienes........................... 113
5.7.4. DSC Measurements of Ferrocenyl Functionalized Polydienes............................ 115
5.7.5. TGA Measurem 115
5.8. Conclusion................................................................................................................... 116
5.9. Experimental Part........................................................................................................ 117
5.9.1. Materials............................................................................................................... 117
5.9.1. Synthesis of the Macromonomers........................................................................ 118
5.9.2. Synthesis of Branched (Functionalized) Polydienes............................................ 119
6. Ferrocenyl-Functionalized Hyperbranched Polyglycerols................................................. 120
6.1. Introduction ................................................................................................................. 120
6.1.1. Ferrocene Containing Polymers ........................................................................... 120
6.1.2. Cyclic Voltammetry ............................................................................................. 121
6.2. Synthesis and characterization of PG-Fc Polymers .................................................... 124
6.3. Electrochemical properties of PG-Fc Polymers.......................................................... 130
6.4. Conclusion................................................................................................................... 134
6.6. Experimental Part........................................................................................................ 134
6.6.1. Materials 134
6.6.2. Synthesis of ferrocenyl-functionalized polyglycerols.......................................... 135
6.6.3. MALDI-TOF characterization ............................................................................. 135
6.6.4. Electrochemical characterization ......................................................................... 135
7. Ferrocenyl-Functionalized PS-b-PB Copolymers.............................................................. 137
7.1. Introduction ................................................................................................................. 137
7.1.1. Biosensors ............................................................................................................ 137
7.1.2. Enzyme-Based Electrodes.................................................................................... 138
7.2. Preparation of Ferrocenylsilanes................................................................................. 142
7.3. Preparation of Ferrocenyl-functionalized Blockcopolymers ...................................... 145
7.4. Electrochemical Properties of Ferrocenyl-functionalized Blockcopolymers.............. 148
7.5. Application as Mediators in Biosensors...................................................................... 154
7.5.1. Peroxide Biosensor............................................................................................... 154
7.5.2. Enzyme Based Biosensor..................................................................................... 157
7.6. Conclusion................................................................................................................... 159
7.7. Experimental Part........................................................................................................ 160
7.7.1. Reagents ............................................................................................................... 160
7.7.2. Synthesis of Diferrocenylmethylsilane (HSiMeFc )............................................ 160 2
7.7.3. Synthesis of FerrocenyldimeiMe Fc) 161 2
7.7.4. Synthesis of FerrocenyldimeiMe Fc) 161 2
8. Summary and Conclusions................................................................................................. 162
8.1. Amphiphilic Block Copolymers.................................................................................. 162
8.2. Branched Polydienes................................................................................................... 166
8.3. Ferrocenyl-Functionalized Hyperbranched Polyglycerols.......................................... 172
8.4. Ferrocenyl-Functionalized PS-b-PB Copolymers....................................................... 174
9. Methods and Instrumentation............................................................................................. 178
10. Appendix .......................................................................................................................... 183
2TABLE OF CONTENTS
11. Curriculum Vitae.............................................................................................................. 187
12. References ........................................................................................................................ 190






3SYMBOLS AND ABBREVIATIONS
ADH alcohol dehydrogenase
AFM atomic force microscopy
CV cyclic voltammetry
DB degree of branching
DBU 1,8-diazabicyclo[5.4.0]undec-7-ene
DIC Diisopropylcarbodiimide
DLS dynamic light scattering
DMF dimethylformamide
DNA deoxyribonucleic acid
DPTS 4-(Dimethylamino)pyridinium 4-toluenesulfonate
DSC differential scanning calometry
EDC endocrine-disrupting compound
EDTA ethylenediaminetetraacetic acid
EEGE ethoxy ethyl glycidyl ether
ESI-MS electron spray ionization mass spectrometry
Fc ferrocene
[η] intrinsic viscosity
h hour
HOPG highly-ordered pyrolytic graphite
HPLC high-performance liquid chromatography
HSiMeFc ferrocenyldimethylsilane 2
HSiMeFc diferrocenylmethylsilane 2
hypPG hyperbranched polyglicidol
hypPG-PS-hypPG hypPG-block-polystyrene-block-hypPG copolymer
linPG linear polyglycerol
linPG-PS-linPG linPG-block-polystyrene-block-linPG copolymer
LS light scattering
MALLS multi angle laser light scattering
MALDI-ToF Matrix Assisted Laser Desorption/Ionization Time-of-Flight
Me methyl
min minute
M number average of the molecular weight n
MS mass spectrometry
N -PS-N α,ω functional polystyrene with azide endgroups 3 3
4SYMBOLS AND ABBREVIATIONS
NADH dihydronicotinamide adenine dinucleotide
NMR nuclear magnetic resonance
PB polybutadiene
PDI polydispersity index
PEEGE poly(ethoxy ethyl glycidyl ether)
PEEGE-PS-PEEGE PEEGE-block-polystyrene-block-PEEGE copolymer
PG polyglycerol
PI polyisoprene
P number average of the degree of polymerization n
PS polystyrene
PS-N polystyrene with azide endgroup 3
PS-linPG polystyrene-block-linear PG copolymer
PS-hypPG polystyrene-block-hyperbranched PG copolymer
PS-PEEGE polystyrene-block-PEEGE copolymer
PS-OH polystyrene with hydroxyl endgroup
PS-Tos polystyrene with tosylate endgroup
R radius of gyration g
R hydrodynamic radius h
RI refractive index
ROMBP ring opening multibranching polymerization
s second
SCVP self-condensing vinyl polymerization
SEC size exclusion chromatography
SLS static light scattering
TBAH tetra-n-butylammonium hexafluorophosphate
TEM transmission electron microscopy
T glass transition temperature g
THF tetrahydrofuran
TCF time correlation function
TEM
TGA thermo gravimetric analysis
TMP 1,1,1-tris(hydroxymethyl)propane
TNG the next generation
Tos-PS-Tos α,ω functional polystyrene with tosylate endgroups
5SYMBOLS AND ABBREVIATIONS
UV-vis ultraviolet-visible
wt.-% weight percent






61. INTRODUCTION
1. Introduction

1.1. Hyperbranched Polymers

1.1.1. Natural Origins

Roughly spoken, a linear polymer can be defined as long chain with two ends. A
branched polymer possesses branching units in addition to the “normal” chain seg-
ments. From these units new linear chains are grown. Depending on the amount of
these branching units, a branched polymer is characterized by multiple chain ends
(termini). Of course, branched or “hyperbranched” polymers have not been invented
by mankind. In fact, Nature is the true outrider concerning the development of ran-
[1-4]domly cascade-branched structures. The most famous examples are glycogen,
9amylopectin and dextran, which are produced on a 10 ton/year scale (Figure 1).


Figure 1 Enzymatic polymerization of α-D-glucopyranose leading to hyperbranched glycogen (ideal-
[5]ized structure). The inset shows a SEM image of a starch grain with layer structure.

The branched structure of these natural products was first identified by Staudinger
[6] [7](1930) and closer examined later on by Meyer and Bernfeld (1940). Nature takes
7