Carbon-13 NMR investigation of local dynamics in bulk polymers at temperatures well above the glass-transition temperature. 3. cis-1,4-Polybutadiene and cis-1,4-polyisoprene

Batie, R. Dejean de la; Lauprêtre, F.; Monnerie, L.

doi:10.1021/ma00191a024

Cited by 82 publications

(68 citation statements)

References 7 publications

(8 reference statements)

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“…The fit was achieved by treating simultaneously the 25 and 50 MHz T 1 data assuming for the motional model a time scale separation between the fast librations and the segmental motions, as was systematically observed in previously studied polymer chains. 9,[15][16][17] The parameters 2 / 1 and a are kept constant over the whole temperature range while 1 is assumed to vary according to Arrhenius' law 1 ϭA exp(E a /k B T). For a given microstructure, common values of the activation energies E a and prefactors A are adopted for both methylene and methine carbons.…”

Section: Resultsmentioning

confidence: 99%

“…The detailed analysis of relaxation data determined in a number of polymer systems, 9,[15][16][17][18][19][20][21][22] either in solution or in bulk at temperatures well above the glass transition temperature, has shown that the local motions observed by 13 C spinlattice relaxation can be satisfyingly described in terms of damped diffusion of bond orientation along the chain sequence, which represents the segmental motions, and independent fast bond librations. 9 The corresponding orientation autocorrelation function is written as…”

Section: -mentioning

confidence: 99%

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Local dynamics of isotactic and syndiotactic polypropylene in solution

Destrée

Lauprêtre

Lyulin

et al. 2000

The Journal of Chemical Physics

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The local dynamics of polypropylene ͑PP͒ in solution is studied by 13 C NMR relaxation and by molecular dynamics ͑MD͒ simulation via the orientational autocorrelation function ͑OACF͒ of C-H bonds. The interpretation protocol of this function proposed by Dejean de la Bâtie, Lauprêtre and Monnerie ͑DLM͒ ͓R. Dejean de la Bâtie, F. Lauprêtre, and L. Monnerie, Macromolecules 21, 2045͑1988͔͒ is applied and tested on new NMR measurements of the various microstructures of polypropylene. This interpretation scheme of the OACF is supported by a detailed study employing simulated PP trajectories in an atomistic heat bath. MD simulations indicate that, quite generally, the correlation time for segmental motions, 1 , extracted from the DLM motional model is closely linked with the mean time between conformational jumps. Both experiments and simulations suggest a slightly higher mobility of meso sequences by comparison with racemic sequences. Our analysis of the microscopic aspects of the segmental dynamics and its manifestation in motional models allows us to trace the microscopic origin of the larger mobility of meso sequences.

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Section: Resultsmentioning

confidence: 99%

Section: -mentioning

confidence: 99%

Local dynamics of isotactic and syndiotactic polypropylene in solution

Destrée

Lauprêtre

Lyulin

et al. 2000

The Journal of Chemical Physics

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“…A similar behavior has been explained with the contribution to 13 C T 1 relaxation of CÀH bond librations. 32,33,30 Indeed, if librations are considered to be independent from and much faster than the main motion (the isobutyl rotation, in our case), then their contribution to the relaxation results in a simple reduction of the theoretical constant C C C exp C ¼ χC theor C with the scaling factor χ < 1. In our case, a scaling factor of 0.25 indicates a significant contribution of librations to relaxation.…”

Section: Quantitative Characterization Of Specific Dynamicmentioning

confidence: 91%

Dynamics by Solid-State NMR: Detailed Study of Ibuprofen Na Salt and Comparison with Ibuprofen

2011

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The various internal rotations and interconformational jumps of the Na-salt form of ibuprofen in the solid state were characterized in detail by means of the simultaneous analysis of a variety of low- and high-resolution NMR experiments aimed at measuring several (13)C and (1)H spectral and relaxation properties at different temperatures and frequencies. The results were first qualitatively analyzed to identify the motions of the different molecular fragments and to assign them to specific frequency regimes (slow, <10(3) Hz; intermediate, 10(3)-10(6) Hz; and fast, >10(6) Hz). Subsequently, a simultaneous fit of the experimental data sets most sensitive to each frequency range was performed by using suitable motional models, thus obtaining, for each motion, correlation times and activation energies. The motions so characterized were: the rotations of the three methyl groups and of the isobutyl group, occurring in the fast regime, and the π-flip of the phenyl ring, belonging to the intermediate motional regime. The results obtained for the Na-salt form were compared with those of the acidic form of ibuprofen, previously obtained from a similar solid-state NMR approach: despite the very similar chemical structure of the two compounds, their dynamic properties in the solid state are noticeably different.

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“…80 Dejean de la Batie et al have also found it necessary to invoke an additional diffusional process in order to account for spin relaxation in polymer chains. 3,10 All of these studies indicate that coupled librational or torsional motion about many bonds can contribute significantly to the decay of the orientational correlation function. Our own analysis of the spin relaxation data for the LCP differs only in that we regard the internal rotation of the phenyl ring as independent from the remaining torsional processes.…”

Section: Model Parametermentioning

confidence: 99%

“…[2][3][4][5] Molecular models for these processes have generally been based on jump motions between rotational isomeric states, [6][7][8] restricted libration about skeletal bonds, 9 or combinations of the two. 3,5,10,11,12 An interesting treatment of internal dynamics in polymer chains based on Brownian diffusion was presented by Edholm and Blomberg. 13 Their model relates both libration and chain isomerization to the intramolecular potential function and an internal diffusion constant.…”

Section: Introductionmentioning

confidence: 99%

Phenyl ring dynamics and chain reorientation in liquid crystal polymers: A deuteron spin relaxation study

Heaton

Kothe

1998

The Journal of Chemical Physics

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Reorientation dynamics in a nematic liquid crystal studied by fast field cycling nuclear magnetic resonance A detailed description of phenyl ring dynamics and spin relaxation in a highly ordered main chain/side chain liquid crystal polymer is presented. Models for the different motional processes are discussed with reference to experimental measurements of the deuteron spectral densities, J M (M 0 ), measured in the smectic A and nematic phases between 330 K and 500 K, and measured as a function of orientation at 410 K, close to the minima in the relaxation times for Zeeman and quadrupolar order, T 1Z and T 1Q . Intramolecular motion of phenyl rings about the para-axis is regarded as a diffusive process in a two-fold symmetric potential. Theoretical analysis of this model provides the rate constants and amplitudes for passage across the potential barriers and libration within the minima. These are governed entirely by the height of the potential barrier, the potential shape, and the diffusion constant. It is demonstrated that other models for the intramolecular ring dynamics cannot simultaneously account for the magnitudes of the observed J M (M 0 ) in the vicinity of the T 1Z and T 1Q minima. Large amplitude reorientation of the polymer chain is regarded as rotational diffusion in an orienting potential. In order to reproduce both the temperature and orientation dependences of the J M (M 0 ), an additional low amplitude motion of the polymer about the main chain axis, with correlation times in the 10 Ϫ9 s regime at Tϳ400 K, must be included. This is modeled as a one-dimensional diffusion process modulated by a harmonic potential, representing torsional motion of the extented polymer chains. Analysis of the experimental deuteron spin relaxation data yields values for the correlation times and amplitudes for each of the individual processes, providing estimates for the parameters describing each of the potentials which modulate the intramolecular and whole molecule motion, as well as the temperature dependences of the various diffusion constants.

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Carbon-13 NMR investigation of local dynamics in bulk polymers at temperatures well above the glass-transition temperature. 3. cis-1,4-Polybutadiene and cis-1,4-polyisoprene

Cited by 82 publications

References 7 publications

Local dynamics of isotactic and syndiotactic polypropylene in solution

Local dynamics of isotactic and syndiotactic polypropylene in solution

Dynamics by Solid-State NMR: Detailed Study of Ibuprofen Na Salt and Comparison with Ibuprofen

Phenyl ring dynamics and chain reorientation in liquid crystal polymers: A deuteron spin relaxation study

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