The development of bioabsorbable hydrogels on the basis of polyester grafted poly(vinyl alcohol) [Elektronische Ressource] / vorgelegt von Elvira Vidović

Elvira Talapina

Informations

• Publié par: heinrich-heine-universitat_dusseldorf
• Publié le: 01 janvier 2006
• Nombre de lectures: 10
• Langue: English
• Poids de l'ouvrage: 6 Mo

Extrait

The development of bioabsorbable
hydrogels on the basis of polyester
grafted poly(vinyl alcohol)




Von der Fakultät für Mathematik, Informatik und Naturwissenschaften
der Rheinisch-Westfälischen Technischen Hochschule Aachen zur
Erlangung des akademischen Grades einer Doktorin der
Naturwissenschaften genehmigte Dissertation



vorgelegt von


Master of Science
Elvira Vidovi ć
aus Mostar, Bosnien und Herzegowina



Berichter: Universitätsprofessor Dr. rer. nat. H. Höcker
Universitätsprofessorin Dr. D. Klee



Tag der mündlichen Prüfung: 04. September 2006


Diese Dissertation ist auf den Internetseiten der Hochschulbibliothek online verfügbar.
Acknowledgments


I would like to acknowledge my gratitude to Professor Dr. H. Höcker for his supervision and
constructive criticism for the successful completion of my PhD work, carried out at the
Department of Textile Chemistry and Macromolecular Chemistry, RWTH Aachen, from
January 2002 to January 2005.

I would like to extend my gratitude to Professor Dr. D. Klee, who allowed me to carry out the
PhD work, for her suggestions and help.

I owe a lot of thanks to Professor Dr. Z. Janovi ć, whose motivation, constant encouragement
and support, helped me to make this effort and complete the PhD work.

A very special thanks goes to Dr. A. Juki ć who helped me out lots of times in different stages
of this work.

I am greatly indebted to Dr. P. Dalton for his assistance and encouragement.

Many hearty thanks to all my colleagues working at the German Wool Research Institute and
at the Department of Textile Chemistry and Macromolecular Chemistry, RWTH Aachen, for
their cooperation and friendly discussions. In particular, I am grateful to my colleague, Dr.
Carla Terenzi for her backing and understanding during the entire PhD work.
Contents
Abbreviations and symbols IV
1. Introduction 1
1.1 Biomaterials 1
1.1.1 The influence of different parameters on properties 3
1.1.2 Biodegradable materials 4
1.2 Hydrogels 6
1.2.1 The diverse application of hydrogels 6
1.2.2 The degree of swelling 8
2. Aim and concept of the thesis 9
3. Synthesis of networks based on poly(rac-lactide) or poly(rac-lactide-co-glycolide)
with poly(vinyl alcohol) 12
3.1 Ring-opening polymerization (ROP) of cyclic esters 12
3.2 Ring-opening polymof lactide and glycolide 15
3.3 Transformation reaction of end groups 15
3.4 The reaction of grafting of poly(lactide) or poly(lactide-co-glycolide) oligomers
onto poly(vinyl alcohol) and crosslinking 16
4. Characterization of networks 18
4.1 Synthesis of networks 18
4.2 IR analysis of networks 26
4.3 Thermal properties of networks 30
4.3.1 Thermogravimetry (TGA) 30
4.3.2 Differential scanning calorimetry (DSC) 33
4.3.2.1 Influence of the length of polyester chains on the thermal properties
of networks 33
4.3.2.2 Influence of glycolide content on the thermal properties of networks 36
4.3.2.3 Influence of the degree of grafting on the thermal properties
of networks 36
4.4 Mechanical properties of hydrogels 37
4.5 Surface properties of hydrogels 41
4.6 Biocompatibility 42
I5. Controlled degradation of hydrogels 45
5.1 Mass loss of degraded hydrogels 45
5.1.1 Influence of the length of the polyester chains 45
5.1.2 Influence of the composition of the polyester chains 48
5.1.3 Influence of the degree of grafting 49
5.1.4 Influence of degradation conditions 50
5.2 Swelling of degraded hydrogels 53
5.2.1 Influence of the length of the polyester chains 53
5.2.2 Influence of the composition of the polyester chains 56
5.2.3 Influence of the degree of grafting 58
5.2.4 Influence of degradation conditions 60
5.3 Topography of degraded networks 61
5.3.1 Influence of the length of the polyester chains 71
5.3.2 Influence of the composition of the polyester chains 71
5.3.3 Influence of the degree of grafting 72
5.3.4 Influence of degradation conditions 73
5.4 Mechanical properties of degraded hydrogels 75
5.4.1 Influence of the length of polyester grafts on the mechanical properties
of degraded hydrogels 75
5.4.2 Influence of the composition of polyester chains 77
5.4.3 Influence of the degree of grafting 82
5.5 Surface properties of degraded hydrogels 86
5.6 IR analysis of degraded networks 90
5.7 Thermal properties of degraded networks 97
5.7.1 Thermogravimetry (TGA) 97
5.7.2 Differential scanning calorimetry (DSC) 102
6. Summary 104
7. Experimental Part 108
7.1 Materials 108
7.2 Synthesis 108
7.2.1 Ring opening polymerization 108
7.2.2 Transformation of hydroxy into carboxylic end groups 109
7.2.3 Grafting of poly(rac-lactide) or poly(rac-lactide-co-glycolide) chains
onto the poly(vinyl alcohol) backbone 110
II7.2.4 Crosslinking of hydrogels 111
7.3 Characterization methods 112
7.3.1 Nuclear magnetic resonance (NMR) 112
7.3.2 Infrared spectroscopy (IR) 112
7.3.3 Thermogravimetry (TGA) 113
7.3.4 Differential scanning calorimetry (DSC) 113
7.3.5 Tensile strength measurements 113
7.3.6 Contact angle measurements 113
7.3.7 Biocompatibility test 114
7.3.8 Hydrolytical degradation experiment 115
7.3.9 Weight loss of hydrogels during degradation 115
7.3.10 Gravimetrical determination of the degree of swelling 115
7.3.11 Scanning electron microscopy (SEM) 116
8. Literature 117
9. Appendix 121
IIIAbbreviations and symbols

2 A surface area in m0
A area of the particular stretching band in relative units
AIBN 2,2 ′-azobis(2-methylpropionitrile)
DA degree of acetate groups in %
DCC dicyclohexyl carbodiimide
DEE diethyl ether
DG experimental degree of grafting in % exp
DG theoretical degree of grafting in % the
DH theoretical degree of hydrolysis in %
DMAP 4-(N,N-dimethylamino)pyridine
DMEM Dulbecco’s modified Eagle’s medium
DMSO dimethy sulfoxide
DSC Differential Scanning Calorimetry
DTGA Differentiated ThermoGravimetry Analysis
E E-modulus / Young's modulus in MPa
e.g. exempli gratia
Eq. equation
F force in N
FCS fetal calf serum
Fig. figure
FTIR Fourier Transform Infrared
FTIR-PAS Fourier Transform Infrared-PhotoAcustic Spectroscopy
GA glycolide
HEMA 2-hydroxyethyl methacrylate
hF primary human dermal fibroblasts
HQ hydroquinone
i.e. it is (id est)
IOL intraocular lenses
IUPAC International Union of Pure and Applied Chemistry
LA lactide
m weight of hydrogel sample before degradation in g 0
MAG magnification
m weight of dry hydrogel sample after degradation in g d
m relative weight of sample in g rel
m weight of swollen hydrogel sample in g s
M weight average molecular weight w
N number of repeating units in the graft
NMR Nuclear Magnetic Resonance
p.a. pro analysi
PA polyamide
PBS phosphate buffer solution
IVPC polycarbonate
PDMS poly(dimethyl siloxane)
PE polyethylene
PEG poly(ethylene glycol)
PEO poly(ethylene oxide)
PES polester
PGA poly(glycolide)
PLA poly(D,L-lactide) / poly(rac-lactide)
PLGA poly(lactide-co-glycolide)
PMMA poly(methyl methacrylate)
PP polypropylene
ppm parts per million
PTFE polytetrafluoroethylene
PVA poly(vinyl alcohol)
PVC poly(vinyl chloride)
ROP ring-opening polymerization
RT room temperature in °C
S weight related degree of swelling in %
SEM Scanning Electron Microscopy
T temperature of 10% loss of weight in °C 10%
Tab. table
T glass transition temperature in °C g
TGA ThermoGravimetry Analysis
T temperature of maximum rate of weight loss in °C max
Y residuum at T = 600 °C in % 600 °C
δ chemical shift in ppm
-1 -1ΔC change of specific heat capacity during glass transition in J g K p
ΔW weight loss at T in % max
ε strain %
σ stress in MPa
V1 Introduction

1.1 Biomaterials

In 1986 the Consensus Conference of the European Society for Biomaterials defined a
biomaterial as "a nonviable material used in a medical device intended to interact with
[1]biological systems" .
Another definition of a biomaterial is "any substance (other than a drug) or combination of
substances synthetic or natural in origin which can be used for any period of time as whole or
as a part of a system which treats, augments, or replaces any tissue, organ, or function of the
[2]body" .
The application of biomaterials is diverse: surgical instruments, prostheses, implants,
scaffolds, bone regeneration, artificial hips, artificial organs: kidney, liver, heart auxiliary
devices, vascular stents, catheters, intraocular lenses, plastic and reconstructive surgery and
[3]drug delivery vehicles . They are made of different materials and each has specific
requirements. The requirements for the mechanical and surface properties of materials are
many. The first and most important requirement is that biomaterials must be compatible with