On surface forces and morphology of linear polyelectrolytes physisorbed onto oppositely charged surfaces [Elektronische Ressource] / Stephan Block

Blo

Sujets

• Physik

Informations

• Publié par: ernst-moritz-arndt-universitat_greifswald
• Publié le: 01 janvier 2011
• Nombre de lectures: 23
• Langue: Deutsch
• Poids de l'ouvrage: 12 Mo

Extrait

ON SURFACE FORCES AND MORPHOLOGY OF LINEAR POLYELECTROLYTES
PHYSISORBED ONTO OPPOSITELY CHARGED SURFACES


Inauguraldissertation

zur

Erlangung des akademischen Grades eines

Doktors der Naturwissenschaften (Dr. rer. nat.)

an der

Mathematisch-Naturwissenschaftlichen Fakultät

der

Ernst-Moritz-Arndt Universität Greifswald


vorgelegt von
Stephan Block
geboren am 12. Juli 1978
in Brandenburg a. d. Havel


Greifswald, im August 2010
























Dekan: Prof. Dr. Klaus Fesser

1. Gutachter: Prof. Dr. Christiane. A. Helm

2. Gutachter: Prof. Dr. Hans-Jürgen Butt

Tag der Promotion: 10. Dezember 2010 „Vorschlag“ (Günter Kunert)

Ramme einen Pfahl
in die dahinschießende Zeit.
Durch deine Hand rinnt der Sand
und bildet Formlosigkeiten,
die sogleich auf Nimmerwiedersehen
in sich selbst einsinken:
vertanes Leben.

Was du nicht erschaffst, du
bist es nicht. Dein Sein nur Gleichung
für Tätigsein: Wie will denn,
wer nicht Treppen zimmert,
über sich hinausgelangen?
Wie will heim zu sich selber finden,
der ohne Weggenossen?

Hinterlass mehr als die Spur
deiner Tatze, das Testament
ausgestorbner Bestien, davon die Welt
übergenug schon erblickt.

Ramme einen Pfahl ein. Ramme
einen einzigen, einen neuen Gedanken
als geheimes Denkmal
deiner einmaligen Gegenwart
in den Deich
gegen die ewige Flut







Zitat aus „Die Physiker“ (Friedrich Dürrenmatt)

...
NEWTON Verrückt, aber weise.
EINSTEIN Gefangen, aber frei.
MÖBIUS Physiker, aber unschuldig.
... Contents

Chapter 1. Introduction 1

Chapter 2. Conformation of Linear Polymers in Solution 5
2.1 Conformation of linear neutral polymers: the freely jointed chain 5
2.2 Conformamers: the wormlike chain 6
2.3 Excluded volume and swelling effects 7
2.4 Polyelectrolytes 9
2.5 Change in free energy and entropy on confinement 11

Chapter 3. Surface Forces Mediated by (Poly-)Ions or Neutral Polymers 13
3.1 Derjaguin approximation 13
3.2 Forces between charged planar surfaces immersed in an electrolyte solution 16
3.2.1 Charging of surfaces in solution and the electric double layer 16
3.2.2 Poisson-Boltzmann theory and their linearization 18
3.2.3 Forces between planar charged surfaces 22
3.2.4 Remarks 25

3.3 Forces between surfaces covered by polymers 27
3.3.1 General remarks 27
3.3.2 Adsorbed neutral polymers 29
3.3.3 Adsorbed polyelectrolytes 32
3.3.4 Grafted neutral polymers: mushroom conformation 34
3.3.5 End-grafted neutral polymers brushes 36
3.3.6 End-grafted polyelectrolyte brushes 43
3.3.7 Application of neutral polymer theory to polyelectrolytes 46

3.4 Hydrodynamic forces 48

Chapter 4. Experimental Methods Based on Atomic Force Microscopy (AFM) 51
4.1 AFM setup 51
4.2 Elastic properties of the AFM cantilever: spring constant 53
and mode spectrum
4.3 Direct measurement of surface force profiles using the AFM 58
4.3.1 Measurement and conversion of single force profiles 58
4.3.2 Requirements for quantitative force measurements 62
4.3.3 Measurement of the mode spectrum and the cantilever spring constant 64
4.3.4. Preparation of colloidal probes 67
4.3.5 Averaging of Force Profiles 684.4 Imaging with AFM 71
4.4.1 Contact mode imaging 71
4.4.2 Intermediate- and non-contact mode imaging 72
4.4.3 Resolution of the image 75

Chapter 5. Forces acting between bare and polyelectrolyte coated 77
silica surfaces
5.1 Forces between bare silica surfaces 81
5.1.1 Colloidal probe technique on bare silica surfaces 82
5.1.2 Measurement of tapping mode force curves employing bare silica surfaces 85
5.1.3 Colloidal probe tapping mode (CPTM) 92

5.2 Forces between surfaces covered by linear polyelectrolytes 97
physisorbed from saltfree solution
5.2.1 Forces between surfaces covered with PSS 97
5.2.2 Forces between surfaces covered with PLL 100
5.2.3 Conclusion of this section 104

5.3 Forces between surfaces covered by linear polyelectrolytes 105
physisorbed at 1 M NaCl
5.3.1 Experimental Results 106
5.3.2 Fitting of the AdG theory to the force profiles 110
5.3.3 Parameter plots and scaling laws 113
5.3.4 Model independent master law for the force profiles 115
5.3.5 Discussion of the approach-retraction-cycles 120
5.3.6 Conclusion of this section 124

5.4 Conformation of single PSS layers physisorbed at I = 1 M NaCl 127Ads
5.4.1 Description of symmetric force profiles by the theories of AdG and MWC 130
5.4.2 Comparison of symmetric and asymmetric force profiles 134
5.4.3 Layer penetration using sharp AFM tips 140
5.4.4 Imaging of the physisorbed PSS layers on different length scales 143
5.4.5 Stability of the PSS layers after drying 150
5.4.6 Discussion and Conclusion 151

5.5 Influence of the chain length on the conformation of single PSS layers 155
physisorbed at I = 1 M NaCl Ads
5.5.1 Morphology of the adsorbed PSS layers 157
5.5.2 Quantification of the force profiles 160
5.5.3 Scaling Laws 167
5.5.4 Conclusion of this section 173
5.6 Dependence of the adsorption salt concentration on the conformation 175
of single PSS layers
5.6.1 Surface Morphology for PSS (N = 840) physisorbed at different I 177Ads
5.6.2 Quantification of the surface force created by inhomogeneously physisorbed 181
PSS layers
5.6.3 Discussion of the steric parameters 194
1985.6.4 Discussion of the viscosity η
5.6.5 Discussion, Outlook and Conclusion 201

Chapter 6. Conclusion and Outlook 205

Bibliography

Publications

Vita / Lebenslauf

Declaration / Erklärung

Acknowledgements / Danksagung
Symbols

a Kuhn length
a monomer m
α excluded volume expansion factor
A area of the i-th mode in the power spectral density i
b cantilever width
β dampling coefficient in the oscillator model i
d dimension of the space
D surface- resp. probe-sample-separation
∆ minimum obtainable surface separation
-19e elementary charge ( = 1.609 10 C)
ε dielectric constant of the medium
ε vacuum dielectric constant 0
E Young’s modulus
E(r) electric field at the position r
η viscosity
η viscosity of the fluid around the cantilever fl
f fraction of charged monomers per polyelectrolyte chain
F(D) distance dependent surface force
F(x, t) external applied force per unit length acting on the cantilever
+F attractive force per monomer
F osmotic force (caused by osmotic counterion pressure) osm
F elastic force stretch
F excluded volume repulsive force v
G free energy
−1γ decay length of an exponential decaying function
Γ surface coverage (i.e. coverage area per unit area)
Γ(ω) hydrodynamic function, Γ(ω) = Γ (ω) + i Γ (ω) r i
h cantilever thickness
I bulk salt concentration in medium (i.e. ρ measured in moles per litre) ∞
I moment of inertial
k cantilever spring constant
ik Boltzmann’s constant B
−1κ Debye length
K i-th modified Bessel function of second kind i
l length of the cantilever
l Bjerrum length B
L brush thickness
L contour length C
L electrostatic blob contour length el
L persistence length (including all contributions) p
L intrinsic persistence length p,0
L electrostatic contribution to the persistence length p,el
λ deflection length
*m effective cantilever mass in the oscillator model i
µ cantilever mass per unit length
n pixel count of the AFM image in x- respectively y-direction x/y
υ excluded volume of a monomer
N degree of polymerization
Ω(ω) hydrodynamic correction function
p(D) force per unit area / disjoining pressure
ϕ phase shift in the oscillator model i
φ(r) volume fraction of monomers in a solution
ψ (x) electrostatic potential
q (t) time-dependent part of the i-th cantilever mode i
Q quality factor ofode i
r radial distance
R (perturbed) average end-to-end distance
R colloidal probe radius
R radius of gyration g
R average end-to-end distance 0
R radius of gyration of an ideal chain g,0
Re Reynolds number
ρ cantilever density
ρ density of the fluid around the cantilever fl
ii