Complex dynamics of 1.3.5-trimethylbenzene-2.4.6-D3 studied by proton spin–lattice NMR relaxation and second moment of NMR line

Hołderna-Natkaniec, K.; Latanowicz, L.; Medycki, W.; Świergiel, Jolanta; Natkaniec, I.

doi:10.1016/j.jpcs.2014.10.009

Cited by 3 publications

(6 citation statements)

References 51 publications

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“…The impact of multiple dynamic processes on the M 2 temperature behavior has previously been discussed by several authors [ 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 ]. For two noncorrelated dynamic processes, the M 2 behavior is defined by Equation (A10).…”

Section: Resultsmentioning

confidence: 99%

Heterogeneous Polymer Dynamics Explored Using Static 1H NMR Spectra

Alam

Allers

Jones

2020

IJMS

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NMR spectroscopy continues to provide important molecular level details of dynamics in different polymer materials, ranging from rubbers to highly crosslinked composites. It has been argued that thermoset polymers containing dynamic and chemical heterogeneities can be fully cured at temperatures well below the final glass transition temperature (Tg). In this paper, we described the use of static solid-state 1H NMR spectroscopy to measure the activation of different chain dynamics as a function of temperature. Near Tg, increasing polymer segmental chain fluctuations lead to dynamic averaging of the local homonuclear proton-proton (1H-1H) dipolar couplings, as reflected in the reduction of the NMR line shape second moment (M2) when motions are faster than the magnitude of the dipolar coupling. In general, for polymer systems, distributions in the dynamic correlation times are commonly expected. To help identify the limitations and pitfalls of M2 analyses, the impact of activation energy or, equivalently, correlation time distributions, on the analysis of 1H NMR M2 temperature variations is explored. It is shown by using normalized reference curves that the distributions in dynamic activation energies can be measured from the M2 temperature behavior. An example of the M2 analysis for a series of thermosetting polymers with systematically varied dynamic heterogeneity is presented and discussed.

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Section: Resultsmentioning

confidence: 99%

Heterogeneous Polymer Dynamics Explored Using Static 1H NMR Spectra

Alam

Allers

Jones

2020

IJMS

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“…2 of Ref. 37. The rigid lattice second moment should be reduced to 5.6 G 2 for CH 3 COOK and 8.3 G 2 for (4-CH 3 PyH)SbCl 4 by tunneling jumps at zero K then to 1.6 G 2 and 6 G 2 , respectively at about 20 K (due to jumps over the barrier).…”

Section: Figurementioning

confidence: 86%

“…Jumps over the barrier do not influence the T 1 temperature dependence at the lowest temperatures (because the Arrhenius correlation time is long). A constant value of T 1 has been detected at low temperatures for a number of methyl bearing solids (9,10,26,27,(35)(36)(37)(38)(39)(40)(41)(42)(43).…”

Section: Proton Spin-lattice Relaxation Timementioning

confidence: 96%

“…2 in Ref. 37. Knowledge of the value of M rigid 2 and the temperature dependences of spectral densities permit us to calculate the temperature dependence of M 2 for methyl bearing solids according to Eq.…”

Section: Figurementioning

confidence: 99%

“…Analysis of T 1 and M 2 is performed in a wide temperature range from 10 K to melting temperatures on the basis of the data published earlier for CH 3 COOK (potassium acetate) (26), (4-CH 3 PyH)SbCl 4 (4-methylpyridinium tetrachloroantimonate) (35), [(CH 3 ) 4 P] 3 Sb 2 Br 9 (tris(tetramethylphosphonium) nanobromodiantimonate) (36), and (CH 3 ) 3 C 6 D 3 (1,3,5-trimethylbenzene with deuterated ring protons) (37). These solids contain methyl groups differing by the value of tunnelling splitting.…”

Section: Illustrative Examplesmentioning

confidence: 99%

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Spin‐lattice NMR relaxation and second moment of NMR line in solids containing CH₃ groups

Latanowicz

2015

Concepts Magnetic Resonance

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Complex proton dynamics in solids containing methyl groups are studied over a wide temperature range. Temperature dependences of the proton T 1 relaxation time and the second moment of NMR lines are analyzed. General rules describing the temperature dependencies have been formulated from an analysis of the data. The second moments, M 2 , are correlated with those based on T 1 measurements. The C 3 jumps over the barrier cause a minimum in T 1 below the liquid nitrogen temperature in the presence of tunnelling splitting, or a little above 77 K when tunnelling splitting equals zero. The slope of the high-temperature side of this minimum permits evaluation of the activation energy, which can be used to characterize the tunnelling correlation time. The T 1 is temperature independent in the lowest temperature range, indicating that the tunnelling correlation time assumes a constant value. The tunnelling splitting was estimated as the best fit parameter from the T 1 temperature dependence. The high tunnelling splitting is responsible for T 1 values which are high and independent from the Larmor frequency. The tunnelling jumps reduce the rigid lattice second moment at zero Kelvin. The second reduction is caused by over the barrier C 3 jumps of methyl protons. The tunnelling jumps cease above a temperature T tun . The occurrence of the minimum T 1 above liquid nitrogen temperature, as well as the reduction of the second moment M 2 are due to slowest motion of protons, which can be the isotropic motion of molecule. This minimum is well described by the Woessner method of calculating the correlation function of complex motion. V C 2015 Wiley Periodicals, Inc. Concepts Magn Reson Part A 44A: 214-225, 2015.

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Anomalous proton spin‐lattice relaxation in organic compounds containing methyl groups

Latanowicz

Timoszyk

Kozioł

2018

Concepts Magnetic Resonance

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Temperature measurements of proton spin‐lattice relaxation time performed for acetates ((CH3COO)2Ba, (CH3COO)2Cd, and (CH3COO)2Ca) and acetyl halides ((CH3CO)2O, CH3COBr and CH3COCl) are fitted to a Haupt equation. It is impossible to fit the temperature dependence of T1 protons using the BPP equation. Of importance is the assumption that complex C3 molecular motion of methyl protons takes place. An understanding of the correlation functions of complex C3 reorientation allow for the calculation of the relaxation time, T1, and the second moment of the NMR resonance. The spectral densities are calculated applying Woessner theory of complex motion and assuming a tunneling correlation time implemented from solving the Schrödinger equation. The acceptance of the tunneling correlation time resulting from the Schrödinger equation elucidates the reduction in the second moment at 0 K. The fitting leads to an excellent agreement between the experimental results of T1 temperature dependences and theoretical equations. From this, the tunneling splitting and motional parameters of methyl groups were estimated. The highest value of T1 minimum in the temperature dependence for (CH3COO)2Ba indicates the highest value of tunneling splitting. The smallest value, which is close to the T1 minimum value predicted by the BPP theory for CH3COCl, shows a lack or significantly reduced tunneling splitting. The tunneling jumps disappear at Ttun temperature, which was estimated for all studied compounds. The limitations on the use of Haupt's equation are presented. The presented approach differs from the other theoretical approaches and these differences are evaluated.

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Complex dynamics of 1.3.5-trimethylbenzene-2.4.6-D3 studied by proton spin–lattice NMR relaxation and second moment of NMR line

Cited by 3 publications

References 51 publications

Heterogeneous Polymer Dynamics Explored Using Static 1H NMR Spectra

Heterogeneous Polymer Dynamics Explored Using Static 1H NMR Spectra

Spin‐lattice NMR relaxation and second moment of NMR line in solids containing CH₃ groups

Anomalous proton spin‐lattice relaxation in organic compounds containing methyl groups

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Complex dynamics of 1.3.5-trimethylbenzene-2.4.6-D3 studied by proton spin–lattice NMR relaxation and second moment of NMR line

Cited by 3 publications

References 51 publications

Heterogeneous Polymer Dynamics Explored Using Static 1H NMR Spectra

Heterogeneous Polymer Dynamics Explored Using Static 1H NMR Spectra

Spin‐lattice NMR relaxation and second moment of NMR line in solids containing CH3 groups

Anomalous proton spin‐lattice relaxation in organic compounds containing methyl groups

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Product

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Spin‐lattice NMR relaxation and second moment of NMR line in solids containing CH₃ groups