Linking the glass-forming ability to the Arrhenius crossover of structural relaxation

Ikeda, Masahiro; Aniya, Masaru

doi:10.1016/j.jnoncrysol.2020.120617

Cited by 4 publications

(2 citation statements)

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“… 8 − 10 These transformations delineate collectively the inflection point which is often referred to as the Arrhenius crossover. 11 − 15 …”

Section: Introductionmentioning

confidence: 99%

“…For centuries, supercooled liquids have played a vital role in science, industry, and the day-to-day life of human beings. − They develop when their chemical components fail to create crystallization nuclei below the freezing point. Consequently, the formation of supercooled liquids is often related to the manufacturing of glasses (including the molecular ones) via the vitrification process, in which progressive lowering of the temperature results in dramatic slowing down of molecular motions from nanoseconds to hundreds of seconds around the glass-transition temperature ( T g ). ,, This process takes place in both the nonergodic and ergodic dynamic domains of the ultraviscous liquid, which intersect at the crossover temperature T B . , However, well above T g and T B , there is another characteristic point at which intermolecular organization, molecular motion, and transport coefficients (e.g., diffusivity, viscosity) undergo significant changes. − These transformations delineate collectively the inflection point which is often referred to as the Arrhenius crossover. − …”

Section: Introductionmentioning

confidence: 99%

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Normal-to-Supercooled Liquid Transition in Molecular Glass-Formers: A Hidden Structural Transformation Fuelled by Conformational Interconversion

Nowok,

Grelska,

Dulski

et al. 2024

J. Phys. Chem. B

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Molecular dynamics and transport coefficients change significantly around the so-called Arrhenius crossover in glass-forming systems. In this article, we revisit the dynamic processes occurring in a glass-forming macrocyclic crown thiaether MeBzS 2 O above its glass transition, revealing two crossover temperatures: T B at 309 and T A at 333 K. We identify the second one as the Arrhenius crossover that is closely related to the normal-to-supercooled liquid transition in this compound. We show that the transformation occurring at this point goes far beyond molecular dynamics (where the temperature dependence of structural relaxation times changes its character from activation-like to super-Arrhenius), being reflected also in the internal structure and diffraction pattern. In this respect, we found a twofold local organization of the nearest-neighbor molecules via weak van der Waals forces, without the formation of any medium-range order or mesophases. The nearest surrounding of each molecule evolves structurally in time due to the ongoing fast conformational changes. We identify several conformers of MeBzS 2 O, demonstrating that its lowest-energy conformation is preferred mainly at lower temperatures, i.e., in the supercooled liquid state. Its increased prevalence modifies locally the short-range intermolecular order and promotes vitrification. Consequently, we indicate that the Arrhenius transition is fuelled rather by conformational changes in this glass-forming macrocyclic crown thiaether, which is a different scenario from the so-far existing concepts. Our studies combine broadband dielectric spectroscopy (BDS), X-ray diffraction, Fourier transform infrared (FTIR) spectroscopy, molecular dynamics (MD) simulations, and density functional theory (DFT) calculations.

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“… 8 − 10 These transformations delineate collectively the inflection point which is often referred to as the Arrhenius crossover. 11 − 15 …”

Section: Introductionmentioning

confidence: 99%