Dynamics of the ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulphonyl)imide studied by nuclear magnetic resonance dispersion and diffusion

Seyedlar, Amin Ordikhani; Stapf, Siegfried; Mattea, Carlos

doi:10.1039/c4cp04178j

Cited by 59 publications

(63 citation statements)

References 26 publications

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“…5,9,10 In the case of 1 H, relaxation is caused by fluctuations of the magnetic dipole−dipole interactions and one has to distinguish intra-and intermolecular relaxation pathways. 1,4,8 While the intramolecular contribution R 1 intra (ω) originates from interactions between nuclei belonging to one molecule, the intermolecular relaxation R 1 inter (ω) stems from interactions between nuclei belonging to different molecules.…”

Section: Introductionmentioning

confidence: 99%

Field-Cycling Relaxometry as a Molecular Rheology Technique: Common Analysis of NMR, Shear Modulus and Dielectric Loss Data of Polymers vs Dendrimers

et al. 2015

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Linear poly(propylene glycol) (PPG) as well as a poly(propyleneimine) (PPI) dendrimer with different molar masses (M) are investigated by field-cycling (FC) 1 H NMR, shear rheology (G) and dielectric spectroscopy (DS). The results are compared in a reduced spectral density representation: the quantity R 1 (ωτ α )/R 1 α (0), where R 1 (ωτ α ) is the master curve of the frequency dependent spin−lattice relaxation rate with τ α denoting the local correlation time, is compared to the rescaled dynamic viscosity η′(ωτ α )/η′ α (0). The quantities R 1 α (0) and η′ α (0), respectively, are the zerofrequency limits of a simple liquid reference system. Analogously, the dielectric loss data can be included in the methodological comparison. This representation allows quantifying the sensitivity of each method with respect to the polymer-specific relaxation contribution. Introducing a "cumulative mode ratio" F i (M) for each technique i, which measures the zero-frequency plateau of the rescaled spectral density, characteristic power-law behavior F i (M) ∝ M α i is revealed. In the case of PPG, F NMR (M), F G (M), and F DS (M) essentially agree with predictions of the Rouse model yielding characteristic exponents α i . The crossover to entanglement dynamics is identified by a change in α i around M ≅ 10 kg/mol. The analysis is extended to the dendrimer which exhibits a relaxation behavior reminiscent of Rouse dynamics. Yet, clear evidence of entanglement is missing. The M-dependencies of the dendrimer diffusion coefficient D obtained by pulsed field-gradient NMR and the zero-shear viscosity are found to be D(M) ∝ M −1.6±0.2 and η(M) ∝ M 1.9±0.2 , respectively, in good agreement with our theoretical prediction η(M) ∝ M 1/3 D −1 (M). The close correspondence of R 1 (ωτ α ) with η′(ωτ α ) establishes FC NMR as a powerful tool of "molecular rheology" accessing the microscopic processes underlying macroscopic rheological behavior of complex fluids.

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Section: Introductionmentioning

confidence: 99%

Field-Cycling Relaxometry as a Molecular Rheology Technique: Common Analysis of NMR, Shear Modulus and Dielectric Loss Data of Polymers vs Dendrimers

et al. 2015

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“…Most of the typical room‐temperature ILs often show significant relaxation dispersion even in bulk, which can be fully described by models taking rotational and translational motions into account. One advantage of NMR relaxometry is its possibility to separate these two contributions, and it has been employed in the understanding of glass‐forming liquids and corresponding ILs in the supercooled regime …”

Section: Introductionmentioning

confidence: 99%

“…Recently, the authors have presented a combined study of NMR relaxometry and diffusion measurements, where a deviation of the molecular dynamics from Arrhenius or Vogel–Fulcher–Tammann (VFT) behavior, respectively, has been found in the supercooling regime for the bulk IL 1‐butyl‐3‐methylimidazolium bis(trifluoromethylsulfonyl)imide (Bmim Tf2N). In this work, the same IL is studied confined in Vycor porous glass with a nominal pore diameter of 4 nm, and the results are compared with the bulk behavior, providing an interpretation for the molecular dynamics under solid confinement.…”

Section: Introductionmentioning

confidence: 99%

Nuclear magnetic relaxation and diffusion study of the ionic liquids 1‐ethyl‐ and 1‐butyl‐3‐methylimidazolium bis(trifluoromethylsulfonyl)imide confined in porous glass

Seyedlar

Stapf

Mattea

2019

Magnetic Reson in Chemistry

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The molecular dynamics of the room-temperature ionic liquid 1-butyl-3methylimidazolium bis(trifluoromethylsulfonyl)imide (Bmim Tf2N) confined in porous glass is studied by nuclear magnetic resonance (NMR) relaxometry and diffusometry and is compared with the bulk dynamics over a wide temperature range. The molecular reorientation processes for anions and cations alike are found to be significantly affected by the presence of the glass interface at high temperatures. In this respect, the ionic liquid behaves similarly to polar liquids where proton NMR relaxation is governed by reorientations mediated by translational displacements (RMTDs). This process becomes less significant towards lower temperatures when the characteristic translational correlation times of the ions approach a timescale comparable with those of the RMTD process, and the relaxation dispersions in bulk and in confinement become similar below a temperature corresponding to about 1.2T g , a value where the onset of dynamic heterogeneity has been observed before. The self-diffusion coefficient, on the other hand, is found to be strongly reduced than the bulk within the accessible temperature range of 248 K and above and is significantly slower than expected from the tortuosity effect, suggesting that ion-surface interactions affect the macroscopic properties.

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“…For low‐viscosity molecular liquids, dynamics correlation functions commonly decay exponentially while that is not always the case in ILs, in particular with cations based on imidazolium rings with long alkyl chains, where more complex dynamics is expected. In the case of [Emim][Tf2N], two active NMR nuclei are present, 1 H and 19 F. Regarding dipolar spin interaction, the spin–lattice relaxation of the 1 H in the cation could have as well an intermolecular contribution from the 19 F in the anions . However, at high magnetic field, the 19 F contribution can be neglected.…”

Section: Resultsmentioning

confidence: 99%

Dynamics of binary mixtures of an ionic liquid and ethanol by NMR

Seyedlar

Martins

Sebastião

et al. 2017

Magnetic Reson in Chemistry

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A study of molecular dynamics of the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoro-methylsulphonyl)imide ([Emim][Tf2N]) in solution with deuterated ethanol at different molar concentration and temperatures is presented. The study was performed using H and H nuclear magnetic relaxation and H 1D spectroscopy. The temperature dependence of the spin-lattice relaxation time T of the cations allows the evaluation of the activation energies of the rotational degree of freedom of these molecules. The viscosity in the binary system increases with the concentration of ionic liquid. However, the activation energy in the cation molecules decreases when the concentration of the ionic liquid increases, indicating that the rotational dynamics is facilitated. This behavior is explained from the fact that the presence of the ionic liquid in the system disrupts the degree of intermediate range order expected in the alcohol system. Copyright © 2017 John Wiley & Sons, Ltd.

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Dynamics of the ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulphonyl)imide studied by nuclear magnetic resonance dispersion and diffusion

Cited by 59 publications

References 26 publications

Field-Cycling Relaxometry as a Molecular Rheology Technique: Common Analysis of NMR, Shear Modulus and Dielectric Loss Data of Polymers vs Dendrimers

Field-Cycling Relaxometry as a Molecular Rheology Technique: Common Analysis of NMR, Shear Modulus and Dielectric Loss Data of Polymers vs Dendrimers

Nuclear magnetic relaxation and diffusion study of the ionic liquids 1‐ethyl‐ and 1‐butyl‐3‐methylimidazolium bis(trifluoromethylsulfonyl)imide confined in porous glass

Dynamics of binary mixtures of an ionic liquid and ethanol by NMR

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