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

Boucher, Virginie M.; Cangialosi, Daniele; Alegría, Ángel; Colmenero, Juan

doi:10.1063/1.4977207

Cited by 35 publications

(82 citation statements)

References 84 publications

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“…The increase of  is evident at values of  larger than ∼0.1 s, which is equal to that for which the decoupling -relaxation/vitrification kinetics is observed. This finding is not typically observed in other glass-forming systems at these moderate time scales (2-5), unless the system is subjected to geometrical confinement, as widely reported for polymeric glasses (11,(22)(23)(24)48). Glasses subjected to extremely long annealing would also present a decoupling.…”

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confidence: 48%

“…In this case, much longer observation time scales, for instance, long annealing times in the glassy state (16,17), are required to highlight effects beyond the -process in the (de) vitrification kinetics (18)(19)(20)(21). In contrast, polymers subjected to some specific conditions of geometrical confinement can exhibit heterogeneity of vitrification kinetics on much shorter time scales (22)(23)(24).…”

Section: Introductionmentioning

confidence: 99%

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Vitrification decoupling from α-relaxation in a metallic glass

et al. 2020

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Understanding how glasses form, the so-called vitrification, remains a major challenge in materials science. Here, we study vitrification kinetics, in terms of the limiting fictive temperature, and atomic mobility related to the α-relaxation of an Au-based bulk metallic glass former by fast scanning calorimetry. We show that the time scale of the α-relaxation exhibits super-Arrhenius temperature dependence typical of fragile liquids. In contrast, vitrification kinetics displays milder temperature dependence at moderate undercooling, and thereby, vitrification takes place at temperatures lower than those associated to the α-relaxation. This finding challenges the paradigmatic view based on a one-to-one correlation between vitrification, leading to the glass transition, and the α-relaxation. We provide arguments that at moderate to deep undercooling, other atomic motions, which are not involved in the α-relaxation and that originate from the heterogeneous dynamics in metallic glasses, contribute to vitrification. Implications from the viewpoint of glasses fundamental properties are discussed.

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confidence: 48%

Section: Introductionmentioning

confidence: 99%

Vitrification decoupling from α-relaxation in a metallic glass

et al. 2020

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“…This is the case of freestanding PS films, which exhibit two kinks in their thickness when cooled at 0.5 K min −1 [55]. Stacked PS films aged far from T g for timescales not larger than several days were shown to exhibit two mechanisms of equilibrium recovery, the faster of them manifesting with a broad endothermic overshoot well below T g [56,57].…”

Section: Fig 4 Enthalpy As a Function Of Temperature For A Ptbs Samplementioning

confidence: 98%

Thermodynamic Ultrastability of a Polymer Glass Confined at the Micrometer Length Scale

Monnier

Cangialosi

2018

Phys. Rev. Lett.

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We employ fast scanning calorimetry to assess the thermodynamic state attained after a given cooling rate and the molecular mobility of glassy poly(4-tert-butylstyrene) confined at the micrometer length scale. We show that, for such a large confinement length scale, thermodynamic states with a fictive temperature (T f) 80 K below the polymer glass transition temperature (T g) are attained, which allows to bypass the geological timescales required for bulk glasses. Access to such states is promoted by a fast mechanism of equilibration. Importantly, the tremendous T f decrease takes place while the molecular mobility remains bulklike, indicating marked decoupling between vitrification kinetics and molecular mobility.

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“…This suggested that deviations in physical aging of ultrathin films were solely an effect of their reduced T g , since the driving force for physical aging is largely determined by proximity of aging temperature to T g . As with T g measurements obtained by stacking films, extensive sample preparation limits wide implementation of this technique, with the exception of a study by Boucher et al in which they also measured faster times to equilibrium in confined PS films . Nanocalorimetry shows promise for characterizing single ultrathin films, but it has thus far mostly been used to expand the range of aging times and temperatures of structural recovery measurements in films >1 µm thick .…”

Section: Confined Polymer Propertiesmentioning

confidence: 99%

“…[69] As with T g measurements obtained by stacking films, extensive sample preparation limits wide implementation of this technique, with the exception of a study by Boucher et al in which they also measured faster times to equilibrium in confined PS films. [88] Nanocalorimetry shows promise for characterizing single ultrathin films, but it has thus far mostly been used to expand the range of aging times and temperatures of structural recovery measurements in films >1 µm thick. [89,90] Very recent work by Koh and Simon examined aging in a single 20 nm thick PS film and found faster aging rates, shorter time to equilibrium, and a broader distribution of relaxation times compared to bulk.…”

Section: Physical Agingmentioning

confidence: 99%

21st Century Advances in Fluorescence Techniques to Characterize Glass‐Forming Polymers at the Nanoscale

Burroughs

Christie

Gray

et al. 2017

Macro Chemistry & Physics

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properties. [9,10] While fluorescence has been used extensively to characterize bulk properties of polymers, including glass transition temperature (T g ) [11][12][13] and polymerization conversion, [13] it is particularly well-suited to study polymers at the nanoscale. This is largely due to the fact that fluorescence techniques enable sensitive and location-specific measurements with high resolution.In this review, we focus on the use of both steady-state and transient fluorescence techniques to characterize physical properties of polymers over nanoscale dimensions. This length scale can refer to film thickness in single-component polymer films, interparticle spacing in nanocomposites, domain spacing in phaseseparated block copolymers, and distance from the polymer-polymer interface in multicomponent immiscible blends. Several geometries characterized via fluorescence are shown in Figure 1. Prior to delving into specific contributions, the basic principles and techniques of fluorescence are presented as well as a brief introduction to the behavior of confined polymers. We then present recent advances in fluorescence techniques for polymer physical characterization under confinement with regards to the glass transition temperature, physical aging, mobility and diffusion, and mechanical response. Through this examination of the literature, we illustrate the unique ability of fluorescence to characterize polymers in confined and complex geometries, providing insights into the influences of interfaces and nanostructure on material properties through sensitive, location-specific measurements. We conclude with a view toward future areas of research in which fluorescence has the potential to be impactful. Introduction to FluorescenceWhen a molecule absorbs energy via light, an electron is excited to a higher energy state, returning to the ground state through either radiative or nonradiative deactivation. This electronic excitation and return to the ground state is a combination of three photophysical processes: absorption, luminescence, and nonradiative decay. [33] Fluorescence is a luminescent process in which the excited-state electron returns to the ground state by emitting a photon, i.e., light. As shown in a simplified Jablonski Polymer CharacterizationCharacterization of polymers at the nanometer-length scale has become increasingly important with the growth and expansion of nanotechnology. Due to limitations of sensitivity and specificity that persist with traditional materials characterization techniques, there is a growing need to develop new tools to measure the properties of confined polymer systems. Within the past 20 years, fluorescence characterization techniques have emerged to address this challenge. This review focuses on the employment of fluorescence techniques such as temperature-and time-dependent steady-state intensity, fluorescence recovery after photobleaching, and nonradiative energy transfer to study polymer behavior at the nanoscale. Properties discussed include glass transition temperatur...

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

Cited by 35 publications

References 84 publications

Vitrification decoupling from α-relaxation in a metallic glass

Vitrification decoupling from α-relaxation in a metallic glass

Thermodynamic Ultrastability of a Polymer Glass Confined at the Micrometer Length Scale

21st Century Advances in Fluorescence Techniques to Characterize Glass‐Forming Polymers at the Nanoscale

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