Dynamics of Dimethylbutanols in Plastic Crystalline Phases by Field Cycling <sup>1</sup>H NMR Relaxometry

Carignani, Elisa; Forte, Claudia; Juszyńska-Gałązka, Ewa; Gałązka, Mirosław; Massalska-Arodź, Maria; Mandoli, Alessandro; Geppi, Marco; Calucci, Lucia

doi:10.1021/acs.jpcb.8b06391

Cited by 5 publications

(4 citation statements)

References 71 publications

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“…Therefore, we hypothesise that the NMRD profiles are descriptive of SD and provide additional insight on relaxation mechanism at lower frequencies. We have considered that this mechanism might be that of order director fluctuations (ODFs) or layer undulations (LUs) as commonly observed in liquid crystals and lipid bilayers, having dependencies of

R_{1} \propto 1 / \sqrt{ν}

and R 1 ∝ 1/ ν , respectively.…”

Section: Methodsmentioning

confidence: 99%

“…The ODF can be described by

{(R_{1} (υ))}_{ODF} = \frac{A_{ODF}}{\sqrt{υ}} ([], f ((), \frac{υ_{ODFmax}}{υ}) - f ((), \frac{υ_{ODFmin}}{υ})),

where A ODF is the prefactor depending on temperature, the order parameter, interproton distances, and viscoelastic properties of the material. υ ODFmax and υ ODFmin are the high and low frequency limits, and f (y) is the cut‐off function:

f ((), y) = \frac{1}{π} ([], arctan ((), \sqrt{2 y} + 1) + arctan ((), \sqrt{2 y} - 1) - arctan ((), \frac{\sqrt{2 y}}{y + 1})),

…”

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

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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R_{1} \propto 1 / \sqrt{ν}

and R 1 ∝ 1/ ν , respectively.…”

Section: Methodsmentioning

confidence: 99%

“…The ODF can be described by

{(R_{1} (υ))}_{ODF} = \frac{A_{ODF}}{\sqrt{υ}} ([], f ((), \frac{υ_{ODFmax}}{υ}) - f ((), \frac{υ_{ODFmin}}{υ})),

f ((), y) = \frac{1}{π} ([], arctan ((), \sqrt{2 y} + 1) + arctan ((), \sqrt{2 y} - 1) - arctan ((), \frac{\sqrt{2 y}}{y + 1})),

…”

Section: Methodsmentioning

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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“…Furthermore, they point out that MBBA exhibits a plastic crystalline phase . NMR relaxometry studies of molecular dynamics of plastic crystal phases due to small globular molecules have been reported elsewhere. − Molecular dynamics in the soft crystal, smectic E phase of NCS-substituted biphenyl namely 4-butyl-4′-isothiocyano-1,1′-biphenyl (4TCB) were probed by the analysis of variable-temperature 1 H NMR spin–lattice relaxation time ( T 1 ) data . Earlier thermodynamic and spectroscopic studies have focused on the successive disordering transitions of the alkyl groups in discotic mesogen benzene-hexa- n -hexanoate and concluded the high-temperature solid phase to be a highly disordered crystalline phase concerning conformations of the paraffinic chains .…”

Section: Introductionmentioning

confidence: 99%

“…These authors utilized the Havriliak–Negami (HN) model for treating collective modes contributing to nuclear spin relaxation . Furthermore, a detailed FFC NMR report on the dynamics of small molecules such as dimethylbutanols in plastic crystalline phases from this group was found elsewhere . Stapf et al interpreted the frequency-dependent relaxation of bulk cyclohexane in the plastically crystalline phase in terms of anisotropic rotation and translational diffusion due to molecular jumps between sites of the cubic lattice. , Kruk et al probed the dynamical heterogeneity vs homogeneous motion in molecular crystals by using 1 H NMR relaxometry analysis due to both Cole–Davidson (CD) and BPP models …”

Section: Introductionmentioning

confidence: 99%

Exploring Crystal-Phase Molecular Dynamics of the Low-Viscous Mesogen 6CHBT: A Combined FFC and High-Field NMR Relaxometry Investigation

Phani Kumar,

Lobo,

Mattea

et al. 2024

J. Phys. Chem. B

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The molecular dynamics study of thermotropic mesogens exhibiting the crystal phases is valuable in unraveling the complex global (collective) and local (noncollective) motions executed by liquid crystal molecules, which would further advance the existing knowledge on orientationally disordered crystalline (ODIC) phases. Toward the fulfillment of such a task, a combined nuclear magnetic resonance (NMR) relaxometry approach employing the fast field cycling (FFC) NMR (10 kHz−30 MHz) and highfield pulsed NMR (400 MHz) techniques is utilized to sample the broad frequency range offered by molecular motions in the crystal phase of 4-(trans-4′-n-hexylcyclohexyl)-isothiocyanatobenzene (6CHBT). The validity of the observed relaxation data is tested and interpreted by the Bloembergen−Purcell−Pound (BPP) model involving the superposition of four mutually independent Lorentzian spectral densities, reflecting molecular dynamical processes on different time scales. The salient feature of the detailed analysis reveals that the lengthening of temporal dynamics in the crystal phase due to molecular rotations by jumps, which are of intermolecular origin, is evident and further supports the presence of collective-like local dynamics. The analysis does permit decoupling of the molecular reorientations about their short axes (∼100 ns) as well as long axes (∼50 ns) and methyl group rotations (∼0.5 ns) on distinct time scales. The activation energies for reorientations about the short axes and methyl group rotations are found to be 27.3 ± 2.7 and 15.8 ± 1.1 kJ/mol, respectively. The fast methyl rotations in the crystal phase of 6CHBT obtained from FFC NMR are further well complemented by high-field NMR, where 1 H NMR line shapes are relatively narrow when compared to those of the nematic phase.

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The dynamics of the plastically crystalline phase of cyanoadamantane revisited by NMR line shape analysis and field-cycling relaxometry

Flämig

Fatkullin

Rössler

2019

The Journal of Chemical Physics

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The dynamics of cyanoadamantane (CN-ADA) in its plastically crystalline phase encompasses three processes: overall tumbling of the rigid molecule, rotation around the molecular symmetry axis, and vacancy diffusion. This makes CN-ADA a prototypical case to be studied by field-cycling as well as by conventional NMR relaxometry. Data are collected from 430 K down to about 4 K and frequencies in the range of 10 kHz–56 MHz are covered. The overall tumbling is interpreted as a cooperative jump process preceding along the orthogonal axis of the cubic lattice and exhibiting a temperature independent non-Lorentzian spectral density. Consequently, a master curve is constructed, which yields model-independent correlation times, which agree well with those reported in the literature. It can be interpolated by a Cole-Davidson function with a width parameter βCD = 0.83. The uniaxial rotation persisting in the glassy crystal (T < Tg = 170 K) is governed by a broad distribution of activation energies, g(E). In this case, the standard master curve construction applied for the overall tumbling, for example, fails, as the actually probed distribution of correlation times G(ln τ) strongly changes with temperature. We suggest a scaling method that generally applies for the case that a relaxation process is determined by a distribution of thermally activated processes. Frequency as well as temperature dependence of the relaxation rate can be used to reconstruct g(E). In addition, g(E) is extracted from the proton line-shape, which was measured down to 4 K. Vacancy diffusion governs the relaxation dispersion at highest temperatures; yet, a quantitative analysis is not possible due to instrumental limitations.

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Dynamics of Dimethylbutanols in Plastic Crystalline Phases by Field Cycling ¹H NMR Relaxometry

Cited by 5 publications

References 71 publications

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

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

Exploring Crystal-Phase Molecular Dynamics of the Low-Viscous Mesogen 6CHBT: A Combined FFC and High-Field NMR Relaxometry Investigation

The dynamics of the plastically crystalline phase of cyanoadamantane revisited by NMR line shape analysis and field-cycling relaxometry

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Dynamics of Dimethylbutanols in Plastic Crystalline Phases by Field Cycling 1H NMR Relaxometry

Cited by 5 publications

References 71 publications

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

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

Exploring Crystal-Phase Molecular Dynamics of the Low-Viscous Mesogen 6CHBT: A Combined FFC and High-Field NMR Relaxometry Investigation

The dynamics of the plastically crystalline phase of cyanoadamantane revisited by NMR line shape analysis and field-cycling relaxometry

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Product

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Dynamics of Dimethylbutanols in Plastic Crystalline Phases by Field Cycling ¹H NMR Relaxometry