Comment on “Temperature divergence of the dynamics of a poly(vinyl acetate) glass: Dielectric vs. mechanical behaviors” [J. Chem. Phys. 136, 154901 (2012)]

Richert, Ranko

doi:10.1063/1.4823797

Cited by 22 publications

(24 citation statements)

References 12 publications

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“…Attempts to resolve this fundamental question of τ α (T) divergence from detailed analysis of experimental data thus far provided different conclusions [3][4][5][6]. The authors of [3] found no evidence for the divergence of relaxation time, although they admitted [3]: "It is not possible to rule out that there is a dynamic divergence of the VFT form, but our findings give no indications of such a divergence".…”

Section: Introductioncontrasting

confidence: 55%

Qualitative change in structural dynamics of some glass-forming systems

Novikov

Sokolov

2015

Phys. Rev. E

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Section: Introductioncontrasting

confidence: 55%

Qualitative change in structural dynamics of some glass-forming systems

Novikov

Sokolov

2015

Phys. Rev. E

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“…These issues are currently matter of ongoing debate. 10,82,83 Finally, our results indicate that, in appropriate conditions, glasses exhibiting thermodynamic state with low enthalpy can be achieved. For instance, in the present work we show that 30-95 nm PS films aged for as little as several hours undergo an enthalpy decrease from the glass cooled down at standard rates (20 K/min in the present study) as large as more than 20 J/g, corresponding to a decrease of the fictive temperature (T f ) − that is, the temperature corresponding to the intercept of the extrapolated glass and equilibrium lines for a given glass − as large as ∼70 K. 48 This corresponds to an increase of the density of approximately 10%.…”

Section: Discussionmentioning

confidence: 54%

Complex nonequilibrium dynamics of stacked polystyrene films deep in the glassy state

Boucher¹,

Cangialosi²,

Alegría

et al. 2017

The Journal of Chemical Physics

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We investigate the kinetics of enthalpy recovery in stacked glassy polystyrene (PS) films with thickness from 30 to 95 nm over a wide temperature range below the glass transition temperature (T). We show that the time evolution toward equilibrium exhibits two mechanisms of recovery, in ways analogous to bulk PS. The fast mechanism, allowing partial enthalpy recovery toward equilibrium, displays Arrhenius temperature dependence with low activation energy, whereas the slow mechanism follows pronounced super-Arrhenius temperature dependence. In comparison to bulk PS, the time scales of the two mechanisms of recovery are considerably shorter and decreasing with the film thickness. Scaling of the equilibration times at various thicknesses indicates that the fast mechanism of recovery is compatible with the free volume holes diffusion model. Conversely, the slow mechanism of recovery appears to be accelerated with decreasing thickness more than predicted by the model and, therefore, its description requires additional ingredients. The implications, from both a fundamental and technological viewpoint, of the ability of thin polymer films to densify in relatively short time scales are discussed.

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“…In this figure the scaled equilibrium relaxation times over a wide range of temperatures are showed, in particular below T g . The different trend of the relaxation time found by Richert and co-workers [168,169,171] on one side and McKenna and co-workers [158,172] on the other will be discussed in detail in a subsequent section of the Review (Section 5.3). [168,169] and Zhao and McKenna [158] (reprinted with permission from Ref.…”

Section: Experimental Studiesmentioning

confidence: 90%

“…The apparent discrepancy between these results has very recently promoted the debate on the divergence versus non-divergent scenario of glassy dynamics [171,172]. These contrasting results are summarized in a very recent work [171] and reported in Fig. 10.…”

Section: Experimental Studiesmentioning

confidence: 99%

Dynamics and thermodynamics of polymer glasses

Cangialosi¹

2014

J. Phys.: Condens. Matter

116

112

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The fate of matter when decreasing the temperature at constant pressure is that of passing from gas to liquid and, subsequently, from liquid to crystal. However, a class of materials can exist in an amorphous phase below the melting temperature. On cooling such materials, a glass is formed; that is, a material with the rigidity of a solid but exhibiting no long-range order. The study of the thermodynamics and dynamics of glass-forming systems is the subject of continuous research. Within the wide variety of glass formers, an important sub-class is represented by glass forming polymers. The presence of chain connectivity and, in some cases, conformational disorder are unfavourable factors from the point of view of crystallization. Furthermore, many of them, such as amorphous thermoplastics, thermosets and rubbers, are widely employed in many applications. In this review, the peculiarities of the thermodynamics and dynamics of glass-forming polymers are discussed, with particular emphasis on those topics currently the subject of debate. In particular, the following aspects will be reviewed in the present work: (i) the connection between the pronounced slowing down of glassy dynamics on cooling towards the glass transition temperature (Tg) and the thermodynamics; and, (ii) the fate of the dynamics and thermodynamics below Tg. Both aspects are reviewed in light of the possible presence of a singularity at a finite temperature with diverging relaxation time and zero configurational entropy. In this context, the specificity of glass-forming polymers is emphasized.

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Comment on “Temperature divergence of the dynamics of a poly(vinyl acetate) glass: Dielectric vs. mechanical behaviors” [J. Chem. Phys. 136, 154901 (2012)]

Cited by 22 publications

References 12 publications

Qualitative change in structural dynamics of some glass-forming systems

Qualitative change in structural dynamics of some glass-forming systems

Complex nonequilibrium dynamics of stacked polystyrene films deep in the glassy state

Dynamics and thermodynamics of polymer glasses

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