Brownian dynamics simulations of local motions in polyisoprene

Adolf, David B.; Ediger, M. D.

doi:10.1021/ma00021a018

Cited by 69 publications

(56 citation statements)

References 12 publications

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“…The values of the confinement size were approximately situated between 6 and 7 Å for the diffusion in a restricted environment model. It is interesting to note the agreement between these values with those associated to the typical length scales of the cooperative motions observed above the T g [43,44].…”

Section: Discussionsupporting

confidence: 66%

Localized translational motions in semicrystalline poly(ethylene terephthalate) studied by incoherent quasielastic neutron scattering

et al. 2013

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One of the simplest ways to confine polymeric materials is by self assembling during the crystallization process. The remaining amorphous phase is then constrained by the lamellar crystals. In this manuscript, we aim to shed additional light in the understanding of the amorphous chains dynamics of semicrystalline polymers above the T g by using incoherent quasielastic neutron scattering QENS in a mesoscopic timescale (10 -9 -10 -10 s) on poly(ethylene terephthalate). The observed dynamics is satisfactorily described by a theoretical model that considers that the proton mobility follows a random jump-diffusion in a restricted environment. We demonstrate that the combination of macroscopic with microscopic dynamic tools allows a complete description of the confined dynamics on a paradigmatic semicrystalline polymer like poly(ethylene terephthalate).

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Section: Discussionsupporting

confidence: 66%

Localized translational motions in semicrystalline poly(ethylene terephthalate) studied by incoherent quasielastic neutron scattering

et al. 2013

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“…The a-relaxation is related to the glass transition (T g ) of the material, so this mode is referred to as the "dynamic glass transition" [48][49][50][51]. The "static" T g determined by DSC corresponds to the "dynamic" T g at a frequency of approximately 10 À3 Hz.…”

Section: Dielectric Relaxation Modes Of Macromolecular Systemsmentioning

confidence: 99%

“…The a-mode is attributed to the diffusion of conformational changes along the macromolecular chain (i.e., the segmental motion of the chain). In general, the a-relaxation presents the following characteristics [48][49][50][51]:…”

Section: Dielectric Relaxation Modes Of Macromolecular Systemsmentioning

confidence: 99%

Broadband Dielectric Spectroscopy: A Powerful Tool for the Determination of Charge Transfer Mechanisms in Ion Conductors

Noto

Giffin

Vezzù³

et al. 2012

Solid State Proton Conductors

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Ionically conducting materials (ICMs) are of great importance for the fabrication of portable batteries for electronic devices such as computers, tools, and video and still cameras, and for the development of fuel cell and battery-powered electric vehicles, dye-sensitized solar cells, supercapacitors, and sensors [1].It has been suggested that conductivity in ICMs occurs via a number of different processes. The predominant conductivity processes are attributed to: (a) the migration of ions between coordination sites in the host materials [2][3][4][5], and (b) the increase of conductivity due to relaxation phenomena involving the dynamics of the host materials [2][3][4][5]. Ions "hopping" to new chemical environments can lead to successful charge migration only if ion-occupying domains relax via reorganizational processes [2-5], which generally are coupled with relaxation events associated with the host matrix.In this chapter, the authors concisely describe the instruments used in the comprehensive study of the electric response of ionic conductors. To provide the reader with the basic tools necessary to understand broadband dielectric spectroscopy [6,7], the first part will review the general phenomena and basic theory behind each type of electric response that materials may exhibit when they are subjected to static or dynamic electric fields. This will be achieved by focusing on the practical use of equations, while referring the reader to specialized texts for detailed explanations of the equations. The second part of this chapter

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“…Previous polymer simulations have also revealed differences between the temperature dependence of conformational transition times and C-H vector OACFs. 9 A. Torsional Autocorrelation Function. To better understand the connection between conformational dynamics and spin-lattice relaxation we have investigated the torsional autocorrelation function (TACF) defined as where φ(t) is the dihedral angle for given dihedral of a particular type and the ensemble average is over all dihedrals of that type.…”

Section: Relationship Between Conformational Dynamics and Spin-latmentioning

confidence: 99%

¹³C NMR Spin−Lattice Relaxation and Conformational Dynamics in a 1,4-Polybutadiene Melt

Smith

Borodin

Bedrov³

et al. 2001

Macromolecules

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We have performed molecular dynamics (MD) simulations of a melt of 1,4-polybutadiene (PBD, 1622 Da) over the temperature range 400-273 K. 13 C NMR spin-lattice relaxation times (T1) and nuclear Overhauser enhancement (NOE) values have been measured from 357 to 272 K for 12 different resonances. The T1 and NOE values obtained from simulation C-H vector P2(t) orientational autocorrelation functions were in good agreement with experiment over the entire temperature range. Analysis of conformational dynamics from MD simulations revealed that T1 depends much less strongly on the local chain microstructure than does the mean conformational transition time. Spin-lattice relaxation for a given nucleus could not be associated with the dynamics of any particular dihedral; instead, spinlattice relaxation occurs as the result of multiple conformational events. However, a much closer correspondence was found between torsional autocorrelation times and the C-H vector P 2(t) autocorrelation times upon which T1 depends. Both processes exhibited stronger than exponential slowing with decreasing temperature. The non-Arrhenius temperature dependences of these relaxation times as well as the stretched-exponential character of the autocorrelation functions themselves were found to be consistent with increasing dynamic heterogeneity in conformational transition rates with decreasing temperature.

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Brownian dynamics simulations of local motions in polyisoprene

Cited by 69 publications

References 12 publications

Localized translational motions in semicrystalline poly(ethylene terephthalate) studied by incoherent quasielastic neutron scattering

Localized translational motions in semicrystalline poly(ethylene terephthalate) studied by incoherent quasielastic neutron scattering

Broadband Dielectric Spectroscopy: A Powerful Tool for the Determination of Charge Transfer Mechanisms in Ion Conductors

¹³C NMR Spin−Lattice Relaxation and Conformational Dynamics in a 1,4-Polybutadiene Melt

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Brownian dynamics simulations of local motions in polyisoprene

Cited by 69 publications

References 12 publications

Localized translational motions in semicrystalline poly(ethylene terephthalate) studied by incoherent quasielastic neutron scattering

Localized translational motions in semicrystalline poly(ethylene terephthalate) studied by incoherent quasielastic neutron scattering

Broadband Dielectric Spectroscopy: A Powerful Tool for the Determination of Charge Transfer Mechanisms in Ion Conductors

13C NMR Spin−Lattice Relaxation and Conformational Dynamics in a 1,4-Polybutadiene Melt

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¹³C NMR Spin−Lattice Relaxation and Conformational Dynamics in a 1,4-Polybutadiene Melt