Defect Diffusion Models in NMR and Dielectric Relaxation

Kimmich, Rainer; Voigt, G.

doi:10.1515/zna-1978-1107

Cited by 36 publications

(14 citation statements)

References 11 publications

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“…However, defects "store" length and this means that the annihilation of a defect in a chain embedded in a more or less static matrix requires the correlated creation of a new defect nearby. This is at least a probability statement permitting the assumption of the quasi-stable defects postulated in many defect diffusion models [6], [32].…”

Section: Technical Details and Sample Characterizationmentioning

confidence: 89%

“…With the data of figure 2, we virtually have the spectral density of the y-process. This information prompted us to extend the kink/ crankshaft model to a defect diffusion model with non-Markovian statistics [6]. Previously we also could show that a mechanism of this type completely describes the T,-dispersion of diplamitoyl-lecithin bilayers at 0 ~ i.e.…”

Section: Y-process Of Amorphous Polyethylenementioning

confidence: 98%

“…For polymer chains confined to a "tube", Doi [18] derived the following expression depending on the correlation function of the end-to-end vector ~ (t): Finally we will discuss the center-of-mass selfdiffusion coefficient and present new data recorded by the aid of a modified NMR field-gradient method (19). The correlation function expression for the selfdiffusion coefficient is [1] D = ~ of <F(o).F(t)> dr, (6) where F(t) is the center-of-mass velocity. The above formula has to be analyzed according to the reptation model.…”

Section: M2mentioning

confidence: 99%

“…For comparison we have also plotted the IR-data of Klein [67] and one data point of Bueche [71]. In all cases a dependence The center of mass diffusion coefficient is defined by equation (6). The velocity F of the center of mass can be expressed by the segment velocities F,, so that oo …”

Section: ~ ~ Ngc(t )mentioning

confidence: 99%

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NMR field-cycling relaxation spectroscopy, transverse NMR relaxation, self-diffusion and zero-shear viscosity: Defect diffusion and reptation in non-glassy amorphous polymers

Kimmich

Bachus

1982

Colloid & Polymer Sci

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Molecular weight and frequency dependences, respectively, of the nuclear magnetic relaxation times and the self-diffusion coefficient of polyethylene and polystyrene have been investigated over several orders of magnitude. The relation to viscous behaviour is established. A closed concept is developed. Conclusions are: a) The y-process in amorphous polyethylene can be described by the aid of the limited defect diffusion model. b) The fl-process in the same material is interpreted as limited reptation. The intensity function of this process depends on the amorphous content. c) The three-component description of chain fluctuations already presented in previous papers has been modified in order to account for the precise molecular weight dependences, which now have been measured. Especially we distinguish between internal and whole-chain reptation. A correlation function is derived, which predicts the right limiting behaviour inspite of its semi-empirical character. The three components can be identified by the frequency and molecular weight dependences of the nuclear magnetic relaxation times. d) The molecular weight dependences are subdivided by 3 (spin lattice relaxation), 2 (transverse relaxation), 1 (zero-shear viscosity) and 0 (self-diffusion coefficient) characteristic molecular weights (Me, MBo MA~ ). All of them can be derived as dynamic case transitions. Especially the classical critical molecular weight of the viscosity can be explained by the transition between tube fluctuations governed by internal and wholechain reptation, respectively. The assumption of a structural transition is unnecessary. e) A semi-empirical expression for the zero-shear viscosity is derived for the whole range of chain lengths. The analysis of the molecular weight dependences of the NMR relaxation times straightforwardly leads to those of the zero-shear viscosity. f) Using a NMR field-gradient method, it is shown again that the self-diffusion coefficients of both melt examples obey D ~ M~72~ g) Matrix effects predominantly are due to changes in the free volume.

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Section: Technical Details and Sample Characterizationmentioning

confidence: 89%

Section: Y-process Of Amorphous Polyethylenementioning

confidence: 98%

Section: M2mentioning

confidence: 99%

Section: ~ ~ Ngc(t )mentioning

confidence: 99%

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NMR field-cycling relaxation spectroscopy, transverse NMR relaxation, self-diffusion and zero-shear viscosity: Defect diffusion and reptation in non-glassy amorphous polymers

Kimmich

Bachus

1982

Colloid & Polymer Sci

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“…When the rates are high such that many individual jumps occur during the Larmor period 0 1 ω − , the NSLR can be related to a continuous diffusion [18]. On the other hand, when individual ion jumps modulate the local field at a frequency comparable with or lower than ω 0 , the NSLR is analyzed on the basis of hopping models [19].…”

Section: Effects Of Lithium Ionic Motion On 7 LI Line-shape and Spinlmentioning

confidence: 99%

Lithium ion dynamics in Li2S+GeS2+GeO2 glasses studied using 7Li NMR field-cycling relaxometry and line-shape analysis

Gabriel

Petrov

Kim

et al. 2015

Solid State Nuclear Magnetic Resonance

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We use (7)Li NMR to study the ionic jump motion in ternary 0.5Li2S+0.5[(1-x)GeS2+xGeO2] glassy lithium ion conductors. Exploring the "mixed glass former effect" in this system led to the assumption of a homogeneous and random variation of diffusion barriers in this system. We exploit that combining traditional line-shape analysis with novel field-cycling relaxometry, it is possible to measure the spectral density of the ionic jump motion in broad frequency and temperature ranges and, thus, to determine the distribution of activation energies. Two models are employed to parameterize the (7)Li NMR data, namely, the multi-exponential autocorrelation function model and the power-law waiting times model. Careful evaluation of both of these models indicates a broadly inhomogeneous energy landscape for both the single (x=0.0) and the mixed (x=0.1) network former glasses. The multi-exponential autocorrelation function model can be well described by a Gaussian distribution of activation barriers. Applicability of the methods used and their sensitivity to microscopic details of ionic motion are discussed.

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A Target Diffusion Theory for Nuclear Spin Relaxation in Ionically‐Conducting Glasses

Elliott

Owens

1991

Ber Bunsenges Phys Chem

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A theoretical mechanism is presented for nuclear spin relaxation in ionically‐conducting glasses (or disordered crystals) caused by ionic motion. This is based on the diffusion‐controlled relaxation model previously used to account for electrical relaxation in such materials: relaxation is assumed to occur at particular (interstitialcy) sites, triggered by the arrival of other diffusing ions. The experimental dependence of the spin‐lattice relaxation rate on temperature and ionic concentration can be understood on the basis of this model.

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Defect Diffusion Models in NMR and Dielectric Relaxation

Cited by 36 publications

References 11 publications

NMR field-cycling relaxation spectroscopy, transverse NMR relaxation, self-diffusion and zero-shear viscosity: Defect diffusion and reptation in non-glassy amorphous polymers

NMR field-cycling relaxation spectroscopy, transverse NMR relaxation, self-diffusion and zero-shear viscosity: Defect diffusion and reptation in non-glassy amorphous polymers

Lithium ion dynamics in Li2S+GeS2+GeO2 glasses studied using 7Li NMR field-cycling relaxometry and line-shape analysis

A Target Diffusion Theory for Nuclear Spin Relaxation in Ionically‐Conducting Glasses

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