Martin-Luther- Universität Halle-Wittenberg Institut für Physik NMR group Bias-free determination of homonuclear dipole-dipole coupling constant distributions and Applications to study local stress of polymer chains Kay Saalwächter Martin-Luther- Universität Halle-Wittenberg Institut für Physik NMR group
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Martin-Luther-Universität Halle-Wittenberg Institut für Physik NMR group Bias-free determination of homonuclear dipole- dipole coupling constant distributions.
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Martin-Luther-Universität Halle-Wittenberg Institut für Physik
NMR group
Bias-free determination of homonuclear dipole-dipole coupling constant
distributions and
Applications to study local stress of polymer chains
Kay Saalwächter
Martin-Luther-Universität Halle-Wittenberg Institut für PhysikNMR group
Martin-Luther-Universität Halle-Wittenberg Institut für Physik
NMR group
Dipole-dipole coupling constant distributions
and local stress of polymer chainsKay Saalwächter
• Double-quantum (DQ) NMR
- principles: normalization and distribution analysis
- elastomer applications
- static low-field vs. MAS (BaBa-xy16)
- structure of phosphates
• Chain stretching and orientation in strained elastomers
DQ
DQ reconversionDQ excitation
IMQ/DQ
DQ
Martin-Luther-Universität Halle-Wittenberg Institut für Physik
NMR group
dip(
B0
Dipole-dipole couplings and time evolution
dipolar coupling tensor D
ij/rij3
Dzz
Dxx
Dyy static powderspectrum
Dstat = Dzz 30 kHz!
t
FID
R. Graf et al., Phys. Rev. Lett. 80 (1998) 5783
KS, Progr. NMR Spectrosc. 51 (2007) 1-35
Martin-Luther-Universität Halle-Wittenberg Institut für Physik
NMR group
DQMQ
nDQ
0 2 4 6 8 10 120.0
0.2
0.4
0.6
0.8
1.0n
orm
. in
ten
sity
DQ evolution time / ms
DQ spectroscopy for homonocular dip. couplings
fit
DQ
DQ reconversionDQ excitation
IMQ/DQ
DQ
Martin-Luther-Universität Halle-Wittenberg Institut für Physik
NMR group
DQ spectroscopy and normalization
determined by = ±90° or n180°
DQ
DQ reconversionDQ excitation
IMQ/DQ
DQ
Martin-Luther-Universität Halle-Wittenberg Institut für Physik
NMR group
NMR in entangled melts and networks (=rubbers) above Tg:
Constrained chain motion of polymers
S = Dres/Dstat ~ 10-2
dynamic chain order parameter
b(t)
R
Martin-Luther-Universität Halle-Wittenberg Institut für Physik
NMR group
2
D
Dipole-dipole coupling and chain dynamics/statistics
B0
HH
static limit (glass):D ~ P2(cos )/rHH
3
1
D
freq.
Dstat 30 kHz (!)
powder
average (all
)
network chain, N segmentsdyn. order parameter S = Dres/Dstat
= 3/(5N)
• S and its distribution can be measured by time-domain (MQ) NMR• also accessible: isotropic fraction = sol, network defects chain ends