NMR of elastomers and biological tissues [Elektronische Ressource] / vorgelegt von Radu Fechete

Radu Fechete

Sujets

• Physik
• Gesundheit

Informations

• Publié par: rheinisch-westfalischen_technischen_hochschule_-rwth-_aachen
• Publié le: 01 janvier 2004
• Nombre de lectures: 12
• Langue: English
• Poids de l'ouvrage: 10 Mo

Extrait

NMR of Elastomers and Biological Tissues

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


vorgelegt von

M. Sc. Radu Fechete
aus Reghin, Rumänien







Berichter: Universitätsprofessor Prof. Dr. rer. nat. Bernhard Blümich
Universitätsprofessor Prof. Dr. Dan Eugen Demco

Tag der mündlichen Prüfung: 28. Januar 2004
Diese Dissertation ist auf den Internetseiten der Hochschulbibliothek online verfügbar.















To my family



Content

List of symbols and acronyms …………………………………………………………….. vii
1. Introduction ………………………………………………………………………………. 1
2. NMR of elastomers in homogeneous magnetic fields …………………………………... 5
2.1 Residual dipolar couplings of soft solids by the accordion magic sandwich …………5
2.1.1 Theory of the accordion magic sandwich …………………………………….. 6
2.1.2 Sampling of the magic echo shape by the Hahn echo …………………………9
12.1.3 H residual van Vleck second moments of cross-linked natural rubber ….…. 11
2.2 Chain Orientation and Slow Dynamics in Elastomers by
Mixed Magic-Hahn Echo Decays ……………………………………………………. 13
2.2.1 History of the topic …………………………………………………….…….. 13
2.2.2 Mixed echo decay ……………………………………………………………. 14
2.2.3 Multi-spin residual dipolar Hamiltonian and dipolar correlation function …… 17
2.2.4 Dependence of the residual second van Vleck moment
on cross-link density …………………………………………………………. 21
2.2.5 Parameters of the dipolar correlation functions ………………………………. 22
12.2.6 The functional dependence of H residual second
van Vleck moments on cross-link density …………………………………… 25
2.2.7 The functional dependence of the correlation times on cross-link density …... 28
2.3 Segmental Anisotropy in Strained Elastomers by the Mixed
1Magic-Hahn Echo Decay and H NMR of Multipolar Spin States ………………….. 30
2.3.1 The affine transformation of polymer networks in strained elastomers ……… 30
2.3.2 The statistical distribution function describing
polymer networks in strained elastomers ……………………………………. 31
12.3.3 The λ dependence of the H second van Vleck moment of a
polymer network under external axial deformation oriented
parallel to the magnetic field ………………..……………………………….. 37
2.3.4 The experimental dependence of <M >, τ and ∆ on the elongation ratio λ .. 39 2 c0 ½
2.3.5 The anisotropy of the residual second van Vleek moment ………………….. 41
2.3.4 Anisotropy of the double quantum coherences and dipolar
encoded longitudinal magnetization …………………………………………. 44
ii Content

2.4 Enhanced Sensitivity to Residual Dipolar Couplings by
High-Order Multiple Quantum Coherences ………………………………………… 48
2.4.1 Excitation and detection of four quantum nuclear
ordered states for a quadrupolar nuclear spin I = 2 …………………………. 49
2.4.2 The Numerical simulations …………………………………………………... 54
2.4.3 Experimental investigation …………………………………………………… 55
12.5 Magnetization Transfer by H double-quantum 2D MAS edited spectra …………… 58
2.5.1 The chemical shift filter ……………………………………………………… 58
12.5.2 Two dimensional H DQ edited spectra ……………………………….……... 62
12.5.3 Chemical shift filtered 2D H DQ encoded spectra ………………………….. 64
2.6 Self-Diffusion Anisotropy of Small Penetrants in Compressed Elastomers ……….. 67
2.6.1 Measurements ………………………………………………………………… 68
2.6.2 Basic theory of self-diffusion in elastomers …………………………………. 68
2.6.3 Results and discussion ……………………………………………………….. 69
2.7 Single shot PGSE measurements of self-diffusion coefficients ……………………. 74
2.7.1 Review of the single scan self-diffusion measurement ………………………. 74
2.7.2 The BURST-PGSSE pulse sequence ………………………………………… 75
2.7.3 The conditions for a linear response of the spin train to
the Burst-pulse sequence ………………………………..………………….... 76
3. Study of collagen fibers of Achilles tendons by Multipolar spin states ……………… 83
3.1 Anisotropy of Collagen Fiber Orientation in Sheep Tendon
1by H Double-Quantum-Filtered NMR Signals ……………………………………. 83
3.1.1 Multipolar spin states in the limit of slow proton exchange ………………... 85
3.1.2 it of fast proton exchange …………………. 89
13.1.3 Study of the Anisotropy of the H Double-Quantum
Filtered NMR Signals ……………………………………………………….. 90
3.1.4 Proton DQ-filtered spectra ………………………………………………….. 92
13.1.5 Anisotropy of the H residual dipolar coupling by doublet
splitting, dipolar encoded longitudinal magnetization, and
double-quantum build-up curves ……………………………………………. 94
13.2 Parameter maps of H residual dipolar couplings in tendon
under mechanical load …………………………………………………………….. 103
3.2.1 Proton DQ-filtered spectra of bound water in tendon
at rest and under compression …………………………………………….. 104 Content iii

3.2.2 DELM decay curves and DQ buildup curves of bound
water in tendon with and without compression ……………………………. 105
3.2.3 Double-quantum decay curve of bound water in tendon
with and without compression ……………………………………………... 106
3.2.4 Proton images and residual dipolar coupling parameter maps
for tendon under com 107
4. NMR in inhomogeneous magnetic fields ……………………………………………. 115
4.1 Characterization of the newest NMR-MOUSE sensors by numerical
simulation of magnetic fields ……………………………………………………... 115
4.1.1 Characterization of the static magnetic field of U-shaped NMR-MOUSE ... 117
4.1.2 Characterization of the static magnetic field of bar magnet NMR-MOUSE ... 121
4.1.3 Characterization of different types of radiofrequency coils ………………… 123
4.2 The NMR signal in strongly inhomogeneous magnetic fields …………………… 133
4.2.1 The theorem of reciprocity ………………………………………………. 133
4.2.2 Free evolution periods and the effect of radio frequency pulses …………. 135
4.2.3 The sensor and receiver filter …………………………………………….. 139
4.2.4 The quadrature detection …………………………………………………. 141
4.2.5 The NMR coefficients ……………………………………………………. 142
4.2.6 Numerical simulations of the Hahn echo and the Stimulated echo ……… 143
4.2.7 Numeulations of CP and CPMG echoes ………………………... 146
4.3 Special pulses designed to save energy and power ……………………………… 148
4.3.1 CPMG pulse sequences with variable refocusing pulses …………………... 148
4.3.2 CPMG pulse sequences with variable distances
between refocusing pulses ………………………………………………… 150
4.3.3 Selective NMR excitation using the DANTE-DANTE
low power pulse sequence …………………………………………………. 153
4.4 Characterization of the Sensitive Volume of NMR-MOUSE sensors ………….. 154
4.4.1 The sensitive volume of the bar-magnet NMR-MOUSE …………………. 154
4.4.2 The sensitive volume of the U-shaped NMR-MOUSE …………………... 156
4.4.3 The effect of spectrometer filters on the sensitive volume ………………… 159
4.4.4 Characterization of the sensitive volume of mobile NMR sensors
for different echoes in the CPMG experiments …………………………….. 160
4.4.5 Characterization of the sensitive volume of mobile NMR sensors
for different excitation and refocusing pulses ……………………………... 163 iv Content

4.4.6 Characterization of the sensitive volume of mobile NMR sensors
for different composite pulses ……………………………………………... 166
4.5 Self-diffusion measurements by a constant-relaxation method
in strongly inhomogeneous magnetic fields ……………………………………... 175
4.5.1 Introduction ………………………………………………………………… 175
4.5.2 Theory and numerical simulation ………………………………………….. 177
4.5.3 Samples …………………………………………………………………….. 184
4.5.4 NMR experiments ………………………………………………………….. 185
4.5.5 Characterization of the gradients of the bar-magnet NMR-MOUSE …….. 186
4.5.6 Self-diffusion measurements ……………………………………………….. 187
4.5.7 Self-diffusion coefficients of liquids with different viscosity ……………… 188
4.5.8 Self-diffusion of toluene in natural rubber samples ………………………... 190
4.5.8 Proton self-diffusion anisotropy of free water in bovine Achilles tendon …. 191
4.6 Elastomers with Industrial applications ………………………………………….. 194
4.6.1 NMR-MOUSE investigation of heterogeneities in elastomers by
transversal relaxation in the rotating frame T ……………………………. 194 1ρ
4.6.2 Investigation of heterogeneities in elastomers
by high field NMR imaging ……………………………………………….. 197
4.6.3 Determination of cross-link density by the NMR-MOUSE ………………. 203
4.6.4 Characterization of thermo-oxidative aging of elastomers
by the NMR-MOUSE …………………………………………………….. 206
5. Conclusions and outlook …………………………………………………………….… 211
6. Appendix
A1 Materials and samples ……………………………………………………………… 215
A2 The magic sandwich propagator …………………………………………………… 216
A3 The mixed magic-Hahn echo decay ……………………………………………….. 218
A4 Affine transformations of the end-to-end vector ………………………………….. 222
A5 The statistical distribution functions of the end-to-end vector and the
azimuthal angle β of polymer networks under external axial deformation ………... 224
A6 The residual