Chapter 13. Field-cycling Relaxometry of Polymers

Stapf, Siegfried; Lozovoi, Artur

doi:10.1039/9781788012966-00322

Cited by 5 publications

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“…In the case of polymers, contributions to R 1 arise from both intrachain (or intrasegment) dipolar couplings, modulated by reorientations ( R 1,intra ), and interchain (or intersegment) couplings, modulated by both reorientational and translational dynamics ( R 1,inter ). Although the intrachain contribution dominates at high frequency, the interchain contribution becomes increasingly important and exceeds the intrachain one at low frequencies. − …”

Section: Theoretical Backgroundmentioning

confidence: 99%

“…1 H FC NMR relaxometry has been indeed extensively applied to study the dynamics of linear polymer melts, both below and above the entanglement limit, especially focusing on testing models on ideal polymers, that is, simple unbranched polymers in the molten state at favorable experimental temperatures. − In particular, 1 H FC NMR relaxometry measurements on several linear polymers have been reviewed by Kimmich and Fatkullin, which, at ωτ s ≪ 1, appear to reveal an universal dispersion behavior of R 1 with characteristic power law regimes R 1 (ω) ∝ ω –γ . These dispersions have been interpreted within Rouse and renormalized Rouse theories for nonentangled and entangled polymers, respectively.…”

Section: Introductionmentioning

confidence: 99%

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Glassy and Polymer Dynamics of Elastomers by ¹H Field-Cycling NMR Relaxometry: Effects of Cross-Linking

et al. 2020

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1H spin lattice relaxation rate (R 1) dispersions were acquired by field-cycling (FC) NMR relaxometry between 0.01 and 35 MHz over a wide temperature range on polyisoprene (IR), polybutadiene (BR), and poly(styrene-co-butadiene) (SBR) rubbers, obtained by vulcanization under different conditions, and on the corresponding uncured elastomers. By exploiting the frequency–temperature superposition principle, χ″(ωτs) master curves were constructed by shifting the total FC NMR susceptibility, χ″(ω) = ωR 1(ω), curves along the frequency axis by the correlation times for glassy dynamics, τs. Longer τs values and, correspondingly, higher glass transition temperatures were determined for the sulfur-cured elastomers with respect to the uncured ones, which increased by increasing the cross-link density, whereas no significant changes were found for fragility. The contribution of polymer dynamics, χ pol ″(ω), to χ″(ω) was singled out by subtracting the contribution of glassy dynamics, χ glass ″(ω), well represented using a Cole–Davidson spectral density. For all elastomers, χ pol ″(ω) was found to represent a small fraction, on the order of 0.05–0.14, of the total χ″(ω), which did not show a significant dependence on cross-link density. In the investigated temperature and frequency ranges, polymer dynamics was found to encompass regimes I (Rouse dynamics) and II (constrained Rouse dynamics) of the tube reptation model for the uncured elastomers and only regime I for the vulcanized ones. This is clear evidence that chemical cross-links impose constraints on chain dynamics on a larger space and time scale than free Rouse modes.

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Section: Theoretical Backgroundmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Glassy and Polymer Dynamics of Elastomers by ¹H Field-Cycling NMR Relaxometry: Effects of Cross-Linking

et al. 2020

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“…1 H longitudinal relaxation is driven by the fluctuations of magnetic dipole-dipole interactions between 1 H-1 H spin pairs under the effect of molecular motions. 1 H FC relaxometry has proven to be particularly useful for the study of dynamics of uncured and crosslinked elastomers, since R 1 depends on different power laws of the Larmor frequency in the different dynamic regimes governing relaxation [71,72]. It has been previously shown that the NMRD curves are dominated by glassy dynamics, and that on the basis of the FTS principle, it is possible to determine τ s values from NMRD curves acquired at different temperatures [42].…”

Section: H Longitudinal Relaxation By Fc Nmrmentioning

confidence: 99%

Influence of Sulfur-Curing Conditions on the Dynamics and Crosslinking of Rubber Networks: A Time-Domain NMR Study

et al. 2022

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The characterization of the structural and dynamic properties of rubber networks is of fundamental importance in rubber science and technology to design materials with optimized mechanical properties. In this work, natural and isoprene rubber networks obtained by curing at three different temperatures (140, 150, and 170 °C) and three different sulfur contents (1, 2, and 3 phr) in the presence of a 3 phr accelerator were studied using a combination of low-field time-domain NMR (TD-NMR) techniques, including 1H multiple-quantum experiments for the measurement of residual dipolar couplings (Dres), the application of the Carr–Purcell–Meiboom–Gill pulse sequence for the measurement of the transverse magnetization decay and the extraction of 1H T2 relaxation times, and the use of field cycling NMR relaxometry for the determination of T1 relaxation times. The microscopic properties determined by TD-NMR experiments were discussed in comparison with the macroscopic properties obtained using equilibrium swelling, moving die rheometer, and calorimetric techniques. The obtained correlations between NMR observables, crosslink density values, maximum torque values, and glass transition temperatures provided insights into the effects of the vulcanization temperature and accelerator/sulfur ratio on the structure of the polymer networks, as well as on the effects of crosslinking on the segmental dynamics of elastomers. Dres and T2 were found to show linear correlations with the crosslink density determined by equilibrium swelling, while T1 depends on the local dynamics of polymer segments related to the glass transition, which is also affected by chemical modifications of the polymer chains occurring during vulcanization.

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“… 47 , 48 Thereby, different dependences of R 1 on the frequency are found in different regimes, depending on the relative weight of the intra- and interchain contributions. 46 − 48 , 61 Since glassy dynamics is strongly prevalent over polymer dynamics, 44 the latter can only be correctly investigated after separation of these two components in FC NMR data, as pointed out by Rössler and co-workers. 45 , 47 , 62 − 68 …”

Section: Introductionmentioning

confidence: 98%

“…1 H FC NMR relaxometry was successfully applied to investigate glassy and polymer dynamics in polymer melts 44 − 48 , 62 − 67 and, less extensively, in cross-linked elastomers. 69 − 73 In particular, in previous work, we investigated the effect of introducing cross-links by sulfur curing on glassy and polymer dynamics of elastomers.…”

Section: Introductionmentioning

confidence: 99%

Glassy and Polymer Dynamics of Elastomers by ¹H-Field-Cycling NMR Relaxometry: Effects of Fillers

et al. 2021

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1 H spin–lattice relaxation rate ( R 1 ) dispersions were acquired by field-cycling (FC) NMR relaxometry between 0.01 and 35 MHz over a wide temperature range on polyisoprene rubber (IR), either unfilled or filled with different amounts of carbon black, silica, or a combination of both, and sulfur cured. By exploiting the frequency–temperature superposition principle and constructing master curves for the total FC NMR susceptibility, χ″(ω) = ω R 1 (ω), the correlation times for glassy dynamics, τ s , were determined. Moreover, the contribution of polymer dynamics, χ pol ″ (ω), to χ″(ω) was singled out by subtracting the contribution of glassy dynamics, χ glass ″ (ω), well represented by the Cole–Davidson spectral density. Glassy dynamics resulted moderately modified by the presence of fillers, τ s values determined for the filled rubbers being slightly different from those of the unfilled one. Polymer dynamics was affected by the presence of fillers in the Rouse regime. A change in the frequency dependence of χ pol ″ (ω) at low frequencies was observed for all filled rubbers, more pronounced for those reinforced with silica, which suggests that the presence of the filler particles can affect chain conformations, resulting in a different Rouse mode distribution, and/or interchain interactions modulated by translational motions.

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Chapter 13. Field-cycling Relaxometry of Polymers

Cited by 5 publications

References 0 publications

Glassy and Polymer Dynamics of Elastomers by ¹H Field-Cycling NMR Relaxometry: Effects of Cross-Linking

Glassy and Polymer Dynamics of Elastomers by ¹H Field-Cycling NMR Relaxometry: Effects of Cross-Linking

Influence of Sulfur-Curing Conditions on the Dynamics and Crosslinking of Rubber Networks: A Time-Domain NMR Study

Glassy and Polymer Dynamics of Elastomers by ¹H-Field-Cycling NMR Relaxometry: Effects of Fillers

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Chapter 13. Field-cycling Relaxometry of Polymers

Cited by 5 publications

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Glassy and Polymer Dynamics of Elastomers by 1H Field-Cycling NMR Relaxometry: Effects of Cross-Linking

Glassy and Polymer Dynamics of Elastomers by 1H Field-Cycling NMR Relaxometry: Effects of Cross-Linking

Influence of Sulfur-Curing Conditions on the Dynamics and Crosslinking of Rubber Networks: A Time-Domain NMR Study

Glassy and Polymer Dynamics of Elastomers by 1H-Field-Cycling NMR Relaxometry: Effects of Fillers

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Glassy and Polymer Dynamics of Elastomers by ¹H Field-Cycling NMR Relaxometry: Effects of Cross-Linking

Glassy and Polymer Dynamics of Elastomers by ¹H Field-Cycling NMR Relaxometry: Effects of Cross-Linking

Glassy and Polymer Dynamics of Elastomers by ¹H-Field-Cycling NMR Relaxometry: Effects of Fillers