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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 Physik NMR group

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Martin-Luther-Universitt Halle-Wittenberg Institut fr Physik NMR group Bias-free determination of homonuclear dipole- dipole coupling constant distributions and Applications to study local stress of polymer chains Kay Saalwchter Martin-Luther-Universitt Halle-Wittenberg Institut fr Physik NMR group Slide 2 Martin-Luther-Universitt Halle-Wittenberg Institut fr Physik NMR group Dipole-dipole coupling constant distributions and local stress of polymer chains Kay Saalwchter 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 I MQ /DQ Slide 3 Martin-Luther-Universitt Halle-Wittenberg Institut fr Physik NMR group dip ( B0B0 Dipole-dipole couplings and time evolution dipolar coupling tensor D i j / r ij 3 D zz D xx D yy static powder spectrum D stat = D zz 30 kHz! t FID R. Graf et al., Phys. Rev. Lett. 80 (1998) 5783 KS, Progr. NMR Spectrosc. 51 (2007) 1-35 Slide 4 Martin-Luther-Universitt Halle-Wittenberg Institut fr Physik NMR group DQ MQ nDQ 024681012 0.0 0.2 0.4 0.6 0.8 1.0 norm. intensity DQ evolution time / ms DQ spectroscopy for homonocular dip. couplings fit DQ DQ reconversionDQ excitation I MQ /DQ Slide 5 Martin-Luther-Universitt Halle-Wittenberg Institut fr Physik NMR group DQ spectroscopy and normalization determined by = 90 or n 180 DQ DQ reconversionDQ excitation I MQ /DQ Slide 6 Martin-Luther-Universitt Halle-Wittenberg Institut fr Physik NMR group NMR in entangled melts and networks (=rubbers) above T g : Constrained chain motion of polymers S = D res / D stat ~ 10 -2 dynamic chain order parameter b(t)b(t) R Slide 7 Martin-Luther-Universitt Halle-Wittenberg Institut fr Physik NMR group 2 D Dipole-dipole coupling and chain dynamics/statistics B0B0 H H static limit (glass): D ~ P 2 (cos )/ r HH 3 1 D freq. D stat 30 kHz (!) powder average (all ) network chain, N segments dyn. order parameter S = D res /D stat = 3/(5 N ) S and its distribution can be measured by time-domain (MQ) NMR also accessible: isotropic fraction = sol, network defects chain ends KS, Prog. Nucl. Magn. Reson. Spetrosc. 51 (2007), 1 R fast-motion limit (rubber T >> T g ): D ~ P 2 (cos ) t P 2 (cos ) freq. D res 100 Hz powder average (all ) Slide 8 Martin-Luther-Universitt Halle-Wittenberg Institut fr Physik NMR group Bimodal networks: test case for inhomogeneities best-fit (monomodal) 0.00.51.01.52.02.53.0 0.0 0.2 0.4 0.6 3.5 net0 (monomodal) net10 net20 net30 net50 net70 net90 net100 DQ intensity % short chains: linear superpositions of experimental data for net0 and net100 PDMS precursors: long chains: 47k short chains: 0.8k excitation time DQ / ms KS, J.-U. Sommer, et al., J. Chem. Phys. 119 (2003), 3468 Slide 9 Martin-Luther-Universitt Halle-Wittenberg Institut fr Physik NMR group Model-heterogeneous networks 040080012001600 0.002.004.006.008 relative amplitude NMR crosslink density D res (~ S ~ 1/ N ) / Hz 0% 10% 20% 30% 50% 70% 90% 100% % short chains KS, J.-U. Sommer, et al., J. Chem. Phys. 119 (2003), 3468 W. Chass, J. Lpez-Valentn, G.D. Genesky, C. Cohen, KS, J. Chem. Phys. 134 (2011) 044907 KS, J. Am. Chem. Soc. 125 (2003), 14684 Bruker minispec mq20, 0.5 T cheap NMR! (~ 75.000.-) PDMS precursors: long chains: 47k short chains: 0.8k residual coupling distributions in end-linked PDMS model networks Slide 10 Martin-Luther-Universitt Halle-Wittenberg Institut fr Physik NMR group Inhomogeneities in rubbers: defects MQ DQ loops dangling ends sol mobile impurities J. Lpez Valentn, P. Posadas, A. Fernndez-Torres, M. A. Malmierca, L. Gonzlez, W. Chass, KS, Macromolecules 43 (2010) 4210. Conventional: accelerator/sulphur (0.2/1) Efficient: accelerator/sulphur (12/1) Peroxide: dicumyl peroxide different cure systems: DQ Slide 11 Martin-Luther-Universitt Halle-Wittenberg Institut fr Physik NMR group Inhomogeneities in natural rubber 0.5 nDQ= DQ/( MQ-tail) R n n n zipping reaction: J. Lpez Valentn, P. Posadas, A. Fernndez-Torres, M. A. Malmierca, L. Gonzlez, W. Chass, KS, Macromolecules 43 (2010) 4210. initial slope reflects crosslink density (~ D res ) and its distribution DQ Slide 12 Martin-Luther-Universitt Halle-Wittenberg Institut fr Physik NMR group CH nDQ CH 2 nDQ Functional-group selectivity: DQ MAS NMR natural rubber network (very homogeneous) 1 H (400 MHz), 10 kHz MAS 1 ppm 234 5 67 CH3CH3 CH2CH2 CHCH static (implies single D res !) nDQ stat fit 281 Hz 0 2 4 DQ evolution time / ms 0.0 0.2 0.4 0.6 norm. intensity Slide 13 Martin-Luther-Universitt Halle-Wittenberg Institut fr Physik NMR group BaBa-xy16 truly broadband DQ MAS NMR y y y xyxy xyy tt tt xx y tt x y y tt x x tt x x tRtR original BaBa see: M. Feike, D. E. Demco, R. Graf, J. Gottwald, S. Hafner, H. W. Spiess J. Magn. Reson. A 122 (1996) 214. broadband BaBa y y y y tt y tt (p x ) y tttt (+ inverted) x x yx x xx y xx (p x )(p y ) (p x ) (p y ) BaBa-xy16 (p x )(p x p y )(p y ) inverted 90x180x virtual (composite) p pulses: 90 - x Slide 14 Martin-Luther-Universitt Halle-Wittenberg Institut fr Physik NMR group MgP 4 O 11, 31 P at 243 MHz (14.1 T) see: M. Feike, D. E. Demco, R. Graf, J. Gottwald, S. Hafner, H. W. Spiess J. Magn. Reson. A 122 (1996) 214. BaBa-xy16 truly broadband DQ MAS NMR 1000200100ppm 8 kHz MAS (impurity) * 1001020kHz 1.21.41.61.82.02.22.42.6 msms * offset variation pulse length (90 1.6 s) cs L /2 = 35 42 kHz 05010050ppm broadband BaBa BaBa-xy16, DQ BaBa-xy16, ref (impurity) BaBa at 30 kHz MAS recoupling time 16 R = 0.533 ms Q2Q2 Q3Q3 Slide 15 Martin-Luther-Universitt Halle-Wittenberg Institut fr Physik NMR group 3540455055 ppm 70 75 80 85 90 95 100 105 110 115 single-quantum shift double-quantum shift Q2Q2 Q3Q3 Q3Q3 Q2Q2 BaBa-xy16 truly broadband DQ MAS NMR 2D DQ corr., 30 kHz MAS recoupling time 16 R = 0.533 ms 1234 Slide 16 Martin-Luther-Universitt Halle-Wittenberg Institut fr Physik NMR group BaBa-xy16 truly broadband DQ MAS NMR 0.00.20.40.60.81.01.21.41.6 0.0 0.2 0.4 0.6 0.8 1.0 norm. intensity DQ evolution time / ms peak 4 peak 3 peak 2 peak 1 DQ build-up / MQ curves norm. intensity MQ DQ broadband BaBa Slide 17 Martin-Luther-Universitt Halle-Wittenberg Institut fr Physik NMR group BaBa-xy16 truly broadband DQ MAS NMR normalized DQ build-up curves: coupling constant estimates (2 nd -moment approx.) 0.00.20.40.60.81.01.21.41.6 0.0 0.2 0.4 0.6 0.8 1.0 norm. intensity DQ evolution time / ms peak 4: 750 Hz peak 3: 780 Hz peak 2: 670 Hz peak 1: 770 Hz expected: D POP (2.9)/2 800 Hz rms-sum: ( D 2 ) /2 (dst. up to 5 ) Q 2 a : 1.34 kHz Q 3 a : 1.47 kHz Q 3 b : 1.38 kHz Q 2 b : 1.20 kHz Q3Q3 Q2Q2 Slide 18 Martin-Luther-Universitt Halle-Wittenberg Institut fr Physik NMR group x z macroscopic microscopic ? R R Unixaxial stretching of polymer networks Slide 19 Martin-Luther-Universitt Halle-Wittenberg Institut fr Physik NMR group macroscopic microscopic x z R R Unixaxial stretching of polymer networks Slide 20 Martin-Luther-Universitt Halle-Wittenberg Institut fr Physik NMR group Unixaxial stretching of polymer networks Sommer, J.-U. et al., Phys. Rev. E 78 (2008) 051803 R f f Segmental (backbone) order parameter S b = second moment of time-averaged orientation distribution b B0B0 the residual dipolar interaction measures the local stress and strain Slide 21 Martin-Luther-Universitt Halle-Wittenberg Institut fr Physik NMR group DQ NMR on stretched networks R f f Bruker minispec mq20 0.5 T (20 MHz) Slide 22 Martin-Luther-Universitt Halle-Wittenberg Institut fr Physik NMR group DQ NMR on stretched networks R f f d i d a d i d o l average stretching: B 0 remove orientation effect! artifical powder response allows distribution analysis! Slide 23 Martin-Luther-Universitt Halle-Wittenberg Institut fr Physik NMR group Local stress/strain distributions in strained rubbers probability vulcanized natural rubber very homogeneous, low defect content =1.0 =4.2 orientation effect removed! increased inhomogeneity, coexistence of almost unchanged and highly strained chains Slide 24 Martin-Luther-Universitt Halle-Wittenberg Institut fr Physik NMR group Comparison with models of rubber elasticity 2.5 2.0 1.5 1.0 0.5 0.0 probabilty 6543210 D res /D res, =1 unstretched tube model phantom model R F R || F R classical affine model stretched R Slide 25 Martin-Luther-Universitt Halle-Wittenberg Institut fr Physik NMR group Confirmation of models of rubber elasticity 3.0 2.5 2.0 1.5 1.0 D res /D res, =1 20151050 elongation 2 - NR1B NR3A NR3B 2.5 2.0 1.5 1.0 0.5 0.0 nI DQ / nI DQ,powder 100806040200 / rel. anisotropy from angle- dependent build-up curves average local stretching from artificial powder nice confirmation of phantom behavior Slide 26 Martin-Luther-Universitt Halle-Wittenberg Institut fr Physik NMR group x z macroscopic microscopic ? Local deformation in filled elastomers hydrodynamic model of polydisperse and undeformable hard spheres: matrix overstrain R. Christensen, Mechanics of Composite Materials Wiley, New York,1979. J. Domurath et al., J. Non-Newtonian Fluid Mech. 171-172 (2012) 8-16. Slide 27 Martin-Luther-Universitt Halle-Wittenberg Institut fr Physik NMR group samples with aggregated filler have a more complex behavior Local deformation in filled elastomers new hydrodyn. model vulcanized natural rubber with eff ~8-19 vol% silica filler effective local stretching loc ~ homogeneous dispersioninhomogeneous dispersion a new, corrected hydrodynamic model is confirmed Slide 28 Martin-Luther-Universitt Halle-Wittenberg Institut fr Physik NMR group Summary and Acknowledgement Dipolar couplings as a probe for molecular dynamics: local dynamics in elastomers, [structure of phosphates] BaBa-xy16: robust broadband homonuclear DQ MAS NMR DIPSHIFT: site-resolved fast-limit and intermediate motions crystallinity and complexity in P3HT slow protein dynamics : thanks to : Frank Lange (U Halle), Robert Graf (MPI-P Mainz) Maria Ott, Martin Schiewek, Horst Schneider (U Halle), Roberto Prez Aparicio, Paul Sotta (CNRS-Rhodia, Lyon)