Molecular view of the isothermal transformation of a stable glass to a liquid

Swallen, Stephen F.; Kearns, Kenneth L.; Satija, Sushil K.; Traynor, Katherine; McMahon, Robert J.; Ediger, M. D.

doi:10.1063/1.2919570

Cited by 46 publications

(56 citation statements)

References 33 publications

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“…As described previously, when thin films of stable glasses are heated above T g they transform into supercooled liquids via a surface-initiated growth front [135,140].…”

Section: Transformation Time Vs Structural Relaxation Timementioning

confidence: 99%

In situ investigation of vapor-deposited glasses of toluene and ethylbenzene via alternating current chip-nanocalorimetry

Ahrenberg

Chua

Whitaker

et al. 2013

The Journal of Chemical Physics

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Vapor-deposited glasses of toluene and ethylbenzene have been characterized by in situ ac chip-nanocalorimetry. The high sensitivity of this method allows the detection of small changes in the heat capacity of nanogram size samples. We observe that vapor-deposited glasses have up to 4% lower heat capacities than the ordinary glass. The largest heat capacity decrease and the most kinetically stable glasses of toluene and ethylbenzene are observed in a range of deposition temperatures between 0.75 Tg and 0.96 Tg. Compared to larger molecules, deposition rate has a minor influence on the kinetic stability of these glasses. For both toluene and ethylbenzene, the kinetic stability is strongly correlated with the heat capacity decrease for deposition temperatures above 0.8 Tg. In addition, ac-nanocalorimetry was used to follow the isothermal transformation of the stable glasses into the supercooled liquid at temperatures slightly above Tg. Toluene and ethylbenzene stable glasses exhibit a constant transformation rate which is consistent with the growth front mechanism recently demonstrated for tris-naphthylbenzene and indomethacin. The kinetic stability of the most stable toluene and ethylbenzene glasses is comparable to that observed for other stable glasses formed by vapor deposition.

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“…As described previously, when thin films of stable glasses are heated above T g they transform into supercooled liquids via a surface-initiated growth front [135,140].…”

Section: Transformation Time Vs Structural Relaxation Timementioning

confidence: 99%

In situ investigation of vapor-deposited glasses of toluene and ethylbenzene via alternating current chip-nanocalorimetry

Ahrenberg

Chua

Whitaker

et al. 2013

The Journal of Chemical Physics

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“…Through the study of these new packing arrangements, we hope to gain further insight into the process of glass formation and the resolution of the Kauzmann entropy crisis. In addition, the interesting properties of these vapor-deposited glasses, including higher density (26,28) better thermal stability (25,27), and reduced vapor uptake (58), will likely be technologically relevant.…”

Section: Nanocrystals?mentioning

confidence: 99%

Physical vapor deposition as a route to hidden amorphous states

Dawson

Kearns

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

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106

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Stable glasses of indomethacin (IMC) were prepared by using physical vapor deposition. Wide-angle X-ray scattering measurements were performed to characterize the average local structure. IMC glasses prepared at a substrate temperature of 0.84 Tg (where Tg is the glass transition temperature) and a deposition rate of 0.2 nm/s show a broad, high-intensity peak at low q values that is not present in the supercooled liquid or melt-quenched glasses. When annealed slightly above Tg, the new WAXS pattern transforms into the melt-quenched glass pattern, but only after very long annealing times. For a series of samples prepared at the lowest deposition rate, the new local packing arrangement is present only for deposition temperatures below Tg ؊20 K, suggesting an underlying first-order liquid-to-liquid phase transition.entropy ͉ glass ͉ liquid-liquid transition ͉ supercooled ͉ X-ray scattering I f a liquid is cooled to just below its melting point, one of two outcomes will be observed. If the liquid readily forms crystal nuclei, then crystals will form and grow. Otherwise, the system will remain in the now metastable liquid state. In the absence of crystallization, further cooling of this supercooled liquid will result in slower dynamics, and eventually, the dynamics will become so slow that the supercooled liquid cannot maintain its equilibrium state (1). At this glass transition temperature (T g ), the system properties deviate from the properties of the supercooled liquid, and a glass is formed.Whereas the liquid-to-crystal transition is a first-order phase transition, the supercooled liquid-to-glass transition is a kinetic event based on relaxation times growing rapidly as the temperature is decreased. A great deal of recent work has been concentrated on understanding the nature of slow dynamics in supercooled liquids (2-11). As a liquid is cooled at lower rates, more time is given for the system to find equilibrium, and thus, T g decreases. For many organic liquids, T g decreases 3-4 K for every order-of-magnitude decrease in the cooling rate. Because there is a practical limit as to how slowly a sample can be cooled, a glass always forms upon cooling (if crystallization does not occur).What if one could cool a supercooled liquid extremely slowly such that equilibrium was always maintained? There are good reasons to believe that something interesting must occur. In 1948, Kauzmann discussed the consequences of very slow cooling for the entropy of a supercooled liquid, which identified the so-called Kauzmann entropy crisis (12). For some liquids, if the entropy is extrapolated to low temperature, it becomes equal to that of the crystal not too far below the conventional T g ; further extrapolation leads to a negative entropy above absolute zero in violation of the third law of thermodynamics. Because this is impossible, it is generally assumed that the extrapolation that produces this crisis must be incorrect, and thus something interesting must occur when a supercooled liquid is cooled very slowly. Several theories...

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“…The stable as-deposited glass was assumed to be 1.5% more dense than the ordinary glass in accordance with previous measurements on TNB vapor-deposited under similar conditions. [31,177] Notably, the Poisson ratio σ has the same value (0.36±0.01) in both stable and ordinary glass samples and increases for the supercooled liquid as expected. [180] In contrast to the results presented here, aging experiments on glassforming systems show only small improvements in mechanical properties during aging.…”

Section: Bls Experiments On Imcmentioning

confidence: 63%

“…It has previously been shown that these deposition conditions produce glasses with low enthalpy, high density, and high kinetic stability. [31,[174][175][176][177] T substrate was controlled by attaching the SiO 2 substrates to a copper temperature stage (Fig. 6.1a).…”

Section: Bls Experiments On Imcmentioning

confidence: 99%

High Frequency Acoustics in Colloid-Based Meso- and Nanostructures by Spontaneous Brillouin Light Scattering

Still

2010

Springer Theses

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Molecular view of the isothermal transformation of a stable glass to a liquid

Cited by 46 publications

References 33 publications

In situ investigation of vapor-deposited glasses of toluene and ethylbenzene via alternating current chip-nanocalorimetry

In situ investigation of vapor-deposited glasses of toluene and ethylbenzene via alternating current chip-nanocalorimetry

Physical vapor deposition as a route to hidden amorphous states

High Frequency Acoustics in Colloid-Based Meso- and Nanostructures by Spontaneous Brillouin Light Scattering

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