Verification of the Long-Range and Localized Dynamics of Molecules in an Amorphous Polymer Matrix

Allen, Geoffrey; Higgins, J. S.

doi:10.1021/ma60059a024

Cited by 20 publications

(11 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Consistent with our results, QENS work on PPO-LiClO 4 found that an exponential correlation function, which is not affected by addition of salt, describes the methyl group jumps. 43,44 However, this study reported a somewhat higher activation energy of 17 kJ/mol.…”

Section: A 2 H Nmr Spin-lattice Relaxationcontrasting

confidence: 55%

“…In harmony with an equal amount of M and B deuterons in the monomeric unit of the studied polymer, we obtain coefficients a M Ϸ a B Ϸ 0.5 from these fits. 43,44 This study reported an activation energy of 17 kJ/ mol. 2, we see that the spin-lattice relaxation time T 1 M decreases upon cooling, indicating 0 Ӷ 1 for the methyl group jumps at the studied temperatures.…”

Section: -4mentioning

confidence: 82%

See 1 more Smart Citation

Ion and polymer dynamics in polymer electrolytes PPO-LiClO4. I. Insights from NMR line-shape analysis

Vogel

Torbrügge

2006

The Journal of Chemical Physics

View full text Add to dashboard Cite

We investigate ion and polymer dynamics in polymer electrolytes PPO-LiClO4 performing 2H and 7Li NMR line-shape analysis. Comparison of temperature dependent 7Li and 2H NMR spectra gives evidence for a coupling of ion and polymer dynamics. 2H NMR spectra for various salt concentrations reveal a strong slowdown of the polymer segmental motion when the salt content is increased. The 2H NMR line shape further indicates that the segmental motion is governed by dynamical heterogeneities. While the width of the distribution of correlation times G(log tau) is moderate for low and high salt content, an extremely broad distribution exists for an intermediate salt concentration of 15:1 PPO-LiClO4. For the latter composition, a weighted superposition of two spectral components, reflecting the fast and the slow polymer segments of the distribution, describes the 2H NMR line shape over a broad temperature range. Analysis of the temperature dependent relative intensity of both spectral components indicates the existence of a continuous rather than a discontinuous distribution G(log tau). Such continuous distribution is consistent with gradual fluctuations of the local salt concentration and, hence, of the local environments of the polymer segments, whereas it is at variance with the existence of large salt-depleted and salt-rich domains featuring fast and slow polymer dynamics, respectively. Finally, for all studied PPO-LiClO4 mixtures, the 2H NMR line shape strongly depends on the echo delay in the applied echo-pulse sequence, indicating that the structural relaxation of the polymer segments involves successive rotational jumps about small angles gamma < 20 degrees .

show abstract

Section: A 2 H Nmr Spin-lattice Relaxationcontrasting

confidence: 55%

Section: -4mentioning

confidence: 82%

Ion and polymer dynamics in polymer electrolytes PPO-LiClO4. I. Insights from NMR line-shape analysis

Vogel

Torbrügge

2006

The Journal of Chemical Physics

View full text Add to dashboard Cite

show abstract

“…The value of t 0 100 fs, from the NS experiment, is of the same order of magnitude as the value of t 0 150 fs from the libration in the simulation, which is again a corroboration of both the experimental results as well as the MD model. The activation energy is in qualitative agreement with the earlier reported value of E A ¼ 16 kJ/mol (6).…”

Section: Discussionsupporting

confidence: 91%

The Segmental and Rotational Dynamics of PPO, Above the Glass‐Transition, Investigated by Neutron Scattering and Molecular Dynamics Simulations

et al. 2005

View full text Add to dashboard Cite

AThe relaxation properties of poly(propylene oxide) at temperatures above the glass-transition temperature are studied by quasi-elastic neutron scattering and molecular dynamics (MD) simulations. The contributions to the dynamic structure factor from the segmental motion and the methyl group jump rotation are separated using a threefold jump-rotation model for the methyl side group motion, with a delta function for the distribution of relaxation times, and a stretched exponential function for the segmental motion.This simple model describes momentum transfer and time dependence of the data over a wide temperature range. The results show that with this separation, both neutron and MD data can be well described, and the analysis of both contributions is necessary in order to obtain reliable results for the segmental relaxation and rotational relaxation times at temperature above T g .

show abstract

“…From early 80's, neutron scattering has been widely used to investigate methyl group dynamics in the quasielastic energy range |hω| < ∼ 2 meV, or by using the FEW technique (see Section II). A huge collection of data has been obtained for several polymer systems, including standard materials as PVAc [89,103], PMMA [20,[22][23][24]34,91,104], poly(propylene oxide) (PPO) [105], poly(vinyl methyl ether) (PVME) [23,25,27,106], polyisoprene (PI) [26,92], neat poly(dimethyl siloxane) (PDMS) [93,[107][108][109], and filled with silica nanoparticles [110], head-to-tail [88,90], and head-to-head (hh) [111] polypropylene (PP), poly(ethylene propylene) (PEP) [111], and poly(methyl phenyl siloxane) (PMPS) confined in silica based nanoporous glasses [112], polymer blends as solution chlorinated polyethylene (SCPE)/PMMA [22,113], polystyrene (PS)/ PVME [114,115], hh-PP/PEP [111], or poly(ethylene oxide) (PEO)/PMMA [116,117], thin film photoresist polymers [118], and other polymer based compounds as polymer electrolites [119][120][121], proteins [122], liquid crystalline polyesters and polyethers [123,124] or propylene gl...…”

Section: Summary Of Experimental Results By Neutron Scattering On Pol...mentioning

confidence: 99%

Neutron scattering investigations on methyl group dynamics in polymers

Colmenero

Moreno

Alegría

2005

Progress in Polymer Science

View full text Add to dashboard Cite

Among the different dynamical processes that take place in polymers, methyl group rotation is perhaps the simplest one, since all the relevant interactions on the methyl group can be condensed in an effective mean-field one-dimensional potential. Recent experimental neutron scattering results have stimulated a new revival of the interest on methyl group dynamics in glasses and polymer systems. The existence of quantum rotational tunnelling of methyl groups in polymers was expected for a long time but only very recently (1998), these processes have been directly observed by high-resolution neutron scattering techniques. This paper revises and summarizes the work done on this topic over last ten years by means of neutron scattering. It is shown that the results obtained in many chemically and structurally different polymers can be consistently described in the whole temperature range -from the quantum tunnelling limit to the classical hopping regime -as well as in the librational spectrum, in terms of the Rotation Rate Distribution Model (RRDM), which was first proposed in 1994. This model introduces a distribution of potential barriers for methyl group rotation, which is associated to the disorder present in any structural glass. The molecular and structural origin of the barrier distribution in polymers is discussed on the basis of a huge collection of investigations reported in the literature, including recent fully atomistic molecular dynamics simulations.

show abstract

Verification of the Long-Range and Localized Dynamics of Molecules in an Amorphous Polymer Matrix

Cited by 20 publications

References 0 publications

Ion and polymer dynamics in polymer electrolytes PPO-LiClO4. I. Insights from NMR line-shape analysis

Ion and polymer dynamics in polymer electrolytes PPO-LiClO4. I. Insights from NMR line-shape analysis

The Segmental and Rotational Dynamics of PPO, Above the Glass‐Transition, Investigated by Neutron Scattering and Molecular Dynamics Simulations

Neutron scattering investigations on methyl group dynamics in polymers

Contact Info

Product

Resources

About