Relationship between the transverse NMR decay and the dipolar interaction in elastomers: a comparison of two models

Knörgen, M.; Menge, H.; Hempel, Günter; Schneider, H.; Ries, Michael E.

doi:10.1016/s0032-3861(02)00203-3

Cited by 25 publications

(31 citation statements)

References 13 publications

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“…For reasons of comparison with the relaxometric study of ref. 26, the main body of data in this paper was measured at 80~ Yet, while the quick decay of SZM Q is compensated for by normalization here, we might hypothesize that relaxometric studies of SBR, in which slow motions are part of a necessarily simplified theoretical description [16], might benefit from raising the temperature even higher, in that model dependences might become weaker. The model used in ref.…”

Section: Comparison Of Unvulcanized and Cross-linked Sbrmentioning

confidence: 80%

“…26 is based on the Anderson-Weiss theory (for details see, e.g., ref. 16), where, unlike the analysis of the normalized DQ intensity, a correlation time of slow, cooperative processes as well as the specific form of the autocorrelation function enters the fitting function and may therefore exert an influence on the final results.…”

Section: Comparison Of Unvulcanized and Cross-linked Sbrmentioning

confidence: 99%

“…Different experimental approaches, most of them on the basis of the analysis of spectral line shapes, Hahn or solid-echo experiments, or a combination of these, have been presented over the last thirty years [2,5,[7][8][9][10][11], and the analysis of Halm echo decays has evolved as a particularly attractive tool for the study of elastomers due to its simplicity, versatility, and low demand on the instrumentation [12][13][14][15][16][17]. The signal functions measured in such experiments are mostly analyzed in terms of a slowly fluctuating residual coupling, where the slow process arises from motions of the topological constraints.…”

Section: Introductionmentioning

confidence: 99%

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Chain order in filled SBR elastomers: a proton multiple-quantum NMR study

et al. 2004

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A series of cross-linked styrene-butadiene rubbers (SBR) filled with different amounts of carbon black and silica are investigated by proton multiple-quantum nuclear magnetic resonance (NMR). The method yields reliable information on residual dipolar couplings and their distribution, which in turn are related to local chain order and the effective cross-link density in these systems. Fundamental differences between the response of a linear precursor, which undergoes reptational motion, and vulcanized SBR are discussed. For the latter, it is found that the average chain order parameter as well as its distribution does not change significantly with the amount and the type of filler. This is in surprising contrast to recent results from Hahn-echo relaxometry applied to the same samples, which indicated a significant filler effect on the cross-link density.

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Section: Comparison Of Unvulcanized and Cross-linked Sbrmentioning

confidence: 80%

Section: Comparison Of Unvulcanized and Cross-linked Sbrmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Chain order in filled SBR elastomers: a proton multiple-quantum NMR study

et al. 2004

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“…It should however be noted that a direct calculation of the entropy from a given S b is a non-trivial and model-dependent undertaking, that has only been attempted for some cases of localized dynamics in proteins. [44,45] To date, the models used to analyze NMR data are based on single chains and assume either (somewhat unphysically) no distribution of the order parameter or the residual coupling [20][21][22]24,25] or use a static average over a Gaussian end-to-end distribution, [5][6][7][8][9][10][11][12]25] PðrÞ…”

mentioning

confidence: 99%

NMR Reveals Non‐Distributed and Uniform Character of Network Chain Dynamics

Saalwächter

Sommer

2007

Macromol. Rapid Commun.

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Results of different NMR investigations of elastomers are reviewed with respect to their significance for statistical models of rubber elasticity. In contrast to earlier work based on lineshape analysis and relaxometry, results of recent multiple‐quantum experiments indicate that the NMR‐detected dynamic chain order parameter, which reflects the conformational space of individual monomer units at which the signal is detected locally, is a rather narrowly distributed quantity. Constraints to the dynamics and the conformations of a network chain thus act uniformly and appear as a dynamic average over chains of different length and with different end‐to‐end separations. All our findings are in good agreement with large‐scale computer simulations. Anomalies on swelling such as chain desinterspersion at the early stages and the appearance of heterogeneities, are also discussed.magnified image

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“…With this, the degree of order of the chain segments was increased due to elongation. Segmental chain order can be studied by different NMR methods like linewidth, spin-spin relaxation time measurements, [12] or multiple quantum buildup curves. [13,14] We choose the latter since it is the most sensitive method.…”

Section: Shape-memory Effectmentioning

confidence: 99%

Solid‐State NMR Characterization of Biodegradable Shape‐Memory Polymer Networks

Bertmer

Adams

Blomenkamp-Höfges³

et al. 2005

Macromolecular Symposia

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Summary: Copolymer networks synthesized from dilactide and diglycolide were characterized by solid-state 13 C CPMAS NMR in terms of composition, cross-link density, and rate of cross-linking by UV irradiation. The latter is directly evident by a signal at 44 ppm in the 13 C NMR spectrum. Comparison of solid-state NMR data with the determination of the gel content revealed that this NMR method is sensitive to the chemical cross-link density whereas the gel content is also influenced by physical constraints such as entanglement. Furthermore, these copolymer networks show a shape-memory effect, i.e. a temporary macroscopic shape can be programmed by heating the network above its glass transition temperature together with fixation during cooling. Reheating without fixation recovers the permanent shape. The recovery of the permanent shape could be followed by 1 H DQ NMR buildup curves for a sample that was stretched by 80%.

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Relationship between the transverse NMR decay and the dipolar interaction in elastomers: a comparison of two models

Cited by 25 publications

References 13 publications

Chain order in filled SBR elastomers: a proton multiple-quantum NMR study

Chain order in filled SBR elastomers: a proton multiple-quantum NMR study

NMR Reveals Non‐Distributed and Uniform Character of Network Chain Dynamics

Solid‐State NMR Characterization of Biodegradable Shape‐Memory Polymer Networks

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