Application of proton field‐cycling<scp>NMR</scp>relaxometry for studying translational diffusion in simple liquids and polymer melts

Flämig, M.; Hofmann, M.; Lichtinger, A.; Rössler, E. A.

doi:10.1002/mrc.4823

Cited by 20 publications

(14 citation statements)

References 77 publications

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“…48,86 We wish to point out that eld-cycling NMR relaxometry is successfully employed to investigate the dynamics of ILs recently. 26,45,47,63,[87][88][89][90][91][92] Although from a theoretical point of view similar in size, the [C 1 C 1 IM] + cation and the [(CH 3 ) 2 PO 4 ] À anion reveal different reorientation mobilities and diffusivities. The [(CH 3 ) 2 PO 4 ] À anion shows a three to ve times faster reorientation at room temperature compared to the cation.…”

Section: Resultsmentioning

confidence: 99%

“…For such systems the molecular motion and relaxation properties can be described more efficiently by a distribution of correlation times rather than a single correlation time and an order parameter. [44][45][46][47][48] Therefore, the empirical Cole-Davidson (CD) approach 49,50 (eqn (9)) is widely used in literature for quantitative analysis of relaxation data with distributed correlation times. In eqn (9) the parameter b (0 < b # 1) describes the width of the distribution and s CD is related to s c by s c ¼ bs CD .…”

Section: T Totalmentioning

confidence: 99%

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Reorientation dynamics and ion diffusivity of neat dimethylimidazolium dimethylphosphate probed by NMR spectroscopy

2019

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Section: Resultsmentioning

confidence: 99%

Section: T Totalmentioning

confidence: 99%

Reorientation dynamics and ion diffusivity of neat dimethylimidazolium dimethylphosphate probed by NMR spectroscopy

2019

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“…Conventionally, the spin–lattice relaxation rate R 1 (ω) is measured as a function of temperature for a few frequencies only, and a model-independent extraction of the underlying spectral density (or of the susceptibility) is elusive. With the advent of the field-cycling (FC) technique − employing commercial , or home-built , relaxometers, the situation improved. Proton FC NMR ,,,, measures the frequency-dependent rate R 1 (ω) typically in a range from 10 kHz to 30 MHz, in home-built machines even from 100 Hz to 40 MHz .…”

Section: Introductionmentioning

confidence: 99%

“…With the advent of the field-cycling (FC) technique − employing commercial , or home-built , relaxometers, the situation improved. Proton FC NMR ,,,, measures the frequency-dependent rate R 1 (ω) typically in a range from 10 kHz to 30 MHz, in home-built machines even from 100 Hz to 40 MHz . Yet, the about 3 frequency decades covered by commercial instruments are still too narrow to access the broad relaxation spectra in viscous liquids.…”

Section: Introductionmentioning

confidence: 99%

Nuclear Spin Relaxation in Viscous Liquids: Relaxation Stretching of Single-Particle Probes

et al. 2021

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Spin-lattice relaxation rates R 1 (ω,T), probed via highfield and field-cycling nuclear magnetic resonance (NMR), are used to test the validity of frequency−temperature superposition (FTS) for the reorientation dynamics in viscous liquids. For several liquids, FTS is found to apply so that master curves can be generated. The susceptibility spectra are highly similar to those obtained from depolarized light scattering (DLS) and reveal an excess wing. Where FTS works, two approaches are suggested to access the susceptibility: (i) a plot of deuteron R 1 (T) vs the spin−spin relaxation rate R 2 (T) and (ii) a plot of R 1 (T) vs an independently measured reference time τ ref (T). Using single-frequency scans, (i) allows one to extract the relaxation stretching as well as the NMR coupling constant. Surveying 26 data sets, we find Kohlrausch functions with exponents 0.39 < β K ≤ 0.67. Plots of the spin−spin relaxation rate R 2 rescaled by the NMR coupling constantas a function of temperature allow one to test how well site-specific NMR relaxations couple to a given reference process. Upon cooling of flexible molecule liquids, the sitespecific dynamics is found to merge, suggesting that near T g the molecules reorient essentially as a rigid entity. This presents a possible resolution for the much lower stretching parameters reported here at high temperatures that contrast with the ones that were reported to be universal in a recent DLS study close to T g . Our analysis underlines that deuteron relaxation is a uniquely powerful tool to probe single-particle reorientation.

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“…The main components of fats, triacylglycerols (TAGs), can be considered to be branched polymers, so it is plausible to hypothesise that their dynamics cover orders of magnitude in time, and thus frequencies, similarly to other polymers, and even phospholipids . Moreover, Eads et al reported that structural differences in TAGs are observable at frequencies between tens to hundreds of kilohertz.…”

Section: Introductionmentioning

confidence: 99%

Early stages of fat crystallisation evaluated by low‐field NMR and small‐angle X‐ray scattering

Ladd-Parada

Povey

Vieira

et al. 2019

Magnetic Reson in Chemistry

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Low‐field time‐domain nuclear magnetic resonance (NMR; 20 MHz) is commonly used in the studies of fats in the form of solid fat content (SFC) measurements. However, it has the disadvantage of low sensitivity to small amounts of crystalline material (0.5%), thus often incorrectly determining crystallisation induction times. From spin–lattice relaxation rate measurements (R1) during the isothermal crystallisation measurements of cocoa butter between 0.01 and 10 MHz using fast field cycling NMR, we learnt previously that the most sensitive frequency region is below 1 MHz. Thus, we focused on analysing our 10‐kHz data in detail, by observing the time dependence of R1 and comparing it with standard SFCNMR and SFC determinations from small‐angle X‐ray scattering (SFCSAXS). Although not reflecting directly the SFC, the R1 at this low frequency is very sensitive to changes in molecular aggregation and hence potentially serving as an alternative for determination of crystallisation induction times. Alongside R1, we also show that SFCSAXS is more sensitive to early stages of crystallisation, that is, standard SFCNMR determinations become more relevant when crystal growth starts to dominate the crystallisation process but fail to pick up earlier crystallisation steps. This paper thus demonstrates the potential of studying triacylglycerols at frequencies below 1 MHz for obtaining further understanding of the early crystallisation stages of fats and presents an alternative and complementary method to estimate SFC by SAXS.

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Application of proton field‐cyclingNMRrelaxometry for studying translational diffusion in simple liquids and polymer melts

Cited by 20 publications

References 77 publications

Reorientation dynamics and ion diffusivity of neat dimethylimidazolium dimethylphosphate probed by NMR spectroscopy

Reorientation dynamics and ion diffusivity of neat dimethylimidazolium dimethylphosphate probed by NMR spectroscopy

Nuclear Spin Relaxation in Viscous Liquids: Relaxation Stretching of Single-Particle Probes

Early stages of fat crystallisation evaluated by low‐field NMR and small‐angle X‐ray scattering

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