Molecular theory for the rheology of glasses and polymers

Cavaillé, J.Y.; Pérez, J.; Johari, G. P.

doi:10.1103/physrevb.39.2411

Cited by 190 publications

(115 citation statements)

References 30 publications

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“…In the recent work [15] de Pablo and coworkers pointed out the possibility of regions of negative shear modulus in quenched amorphous systems -such regions being stabilized by the "normal" material in which they are embedded. The typical size of these regions is much smaller than the size for elastic inhomogeneities discussed in this work, implying they are more likely to be linked to elementary rearrangements taking place at the onset of plastic deformation, which usually imply small numbers of particles [6,7,8,9,24], or even localization along a shear band [10,11]. Such a difference in elastic and plastic deformations was also observed for 2D systems in Ref.…”

Section: Discussionmentioning

confidence: 65%

“…Moreover, the field of plastic deformation of glassy materials, which has attracted considerable attention recently [6,7,8,9,10,11] may be expected to be related to elastic heterogeneities. Other points of interest include the experimental evidence for dynamical heterogeneities in deeply supercooled systems [12], which again could be expected to give rise to "frozen in" heterogeneities in low temperature systems.…”

Section: Introductionmentioning

confidence: 99%

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Continuum limit of amorphous elastic bodies. III. Three-dimensional systems

et al. 2005

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Extending recent numerical studies on two dimensional amorphous bodies, we characterize the approach of elastic continuum limit in three dimensional (weakly polydisperse) Lennard-Jones systems. While performing a systematic finite-size analysis (for two different quench protocols) we investigate the non-affine displacement field under external strain, the linear response to an external delta force and the low-frequency harmonic eigenmodes and their density distribution. Qualitatively similar behavior is found as in two dimensions. We demonstrate that the classical elasticity description breaks down below an intermediate length scale ξ, which in our system is approximately 23 molecular sizes. This length characterizes the correlations of the non-affine displacement field, the self-averaging of external noise with distance from the source and gives the lower wave length bound for the applicability of the classical eigenfrequency calculations. We trace back the "Bosonpeak" of the density of eigenfrequencies (obtained from the velocity auto-correlation function) to the inhomogeneities on wave lengths smaller than ξ.

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Section: Discussionmentioning

confidence: 65%

Section: Introductionmentioning

confidence: 99%

Continuum limit of amorphous elastic bodies. III. Three-dimensional systems

et al. 2005

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“…5,7 In certain theories, localized molecular motions of the ␤ process are seen to be the precursor of the ␣ relaxation. 9,10 These motions also contribute to the entropy of the glass. [11][12][13] These have been connected 14 to the non-Debye temperature dependence of the heat capacity at TϽ1 K, 15 and the onset of their molecular motions on heating has been found to occur over a broad temperature range, with a sigmoid-shape heat capacity increase resembling that observed on glass softening.…”

Section: Introductionmentioning

confidence: 99%

Localized relaxation in a glass and the minimum in its orientational polarization contribution

Johari

Power

Vij

2002

The Journal of Chemical Physics

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The dielectric permittivity and loss spectra of the glassy state of 5-methyl-2-hexanol obtained by quenching it from the liquid state has been studied. In one experiment, the spectra were studied at different temperatures as the quenched sample was heated at 0.1 K/min from 105.3 to 160.5 K. In the second experiment, the quenched sample was heated from 77 to 131.6 K and kept at that temperature for 14.6 ks. The relaxation rate, f m,␤ , the dielectric relaxation strength, ⌬⑀ ␤ , and the distribution of relaxation time parameters, ␣ and ␤, for the Johari-Goldstein process were determined. The parameter ␤ was found to be equal to 1 and independent of both the temperature and time, ⌬⑀ ␤ initially decreased on increasing the temperature, reached a minimum value at ϳ145.6 K, and then increased. The plot of f m,␤ against the reciprocal temperature decreased in slope and at ϳ140 K became linear. This indicates that f m,␤ increases on structural relaxation. In the course of the annealing at 131.6 K, ⌬⑀ ␤ of the quenched sample decreased with time, approaching a plateau value. It is described by an equation, ⌬⑀ ␤ (t)ϭ⌬⑀ ␤ (t→ϱ)ϩ͓⌬⑀ ␤ (tϭ0)Ϫ⌬⑀ ␤ (t →ϱ)͔exp͓Ϫ(t/ )͔, where t is the time, and ͑ϭ3.5 ks͒ is the characteristic time. It is pointed out that contrary to the earlier finding, o-terphenyl shows a ␤ relaxation in the equilibrium liquid state. A consideration of dielectric permittivity arising from small-angle motions of all molecules, which has been suggested as an alternative mechanism for the localized motions seen as ␤ relaxation, indicates that this mechanism is inconsistent with the known increase in the equilibrium permittivity on cooling.

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“…Only a few theoretical models assume explicitly the correlation between α-and JG β-relaxation to account globally for glass-forming dynamics. 19,59,60 According to the point of view of the coupling model (CM), 5,19 the β-process is the primitive motion which initiates the cooperative α-process at particular sites in the disordered structure. The more cooperative the α-process is, the greater is the time-scale separation from the JG β-process.…”

Section: Resultsmentioning

confidence: 99%

Emergence of glassy-like dynamics in an orientationally ordered phase

et al. 2012

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The dynamics of a simple rigid pseudoglobular molecule (2-adamantanone) has been studied by means of dielectric spectroscopy and examined under the constraints imposed by the space group of the crystal structure determined by x-ray powder diffraction. The low-temperature monoclinic structure of 2-adamantanone, with one molecule per asymmetric unit (Z = 1), displays a statistical intrinsic disorder, concerning the site occupancy of the oxygen atom along three different sites. Such a physically identifiable disorder gives rise to large-angle molecular rotations which inherently lead to time-average fluctuations of the molecular dipole, thus contributing to the dielectric susceptibility. The dielectric spectra for the low-temperature "ordered" phase displays a universal feature of glassy-like materials, i.e., coexistence of α-and β-relaxation processes. The former is clearly identified with the strongly restricted reorientational motions within the long-range "ordered" crystalline lattice. The latter, never observed before in fully translationally and highly orientationally ordered phases, displays all the properties of an original Johari-Goldstein β-relaxation, in spite of the strong character of this glass-like phase. These findings can be explained according to the coupling model, applied to such "ordered" phases.

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Molecular theory for the rheology of glasses and polymers

Cited by 190 publications

References 30 publications

Continuum limit of amorphous elastic bodies. III. Three-dimensional systems

Continuum limit of amorphous elastic bodies. III. Three-dimensional systems

Localized relaxation in a glass and the minimum in its orientational polarization contribution

Emergence of glassy-like dynamics in an orientationally ordered phase

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