<i>In situ</i> nanocalorimetry of thin glassy organic films

León-Gutiérrez, E.; García, G.; Lopeandía, A. F.; Fraxedas, Jordi; Clavaguera-Mora, M.T.; Rodríguez‐Viejo, J.

doi:10.1063/1.3009766

Cited by 59 publications

(60 citation statements)

References 22 publications

(28 reference statements)

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“…37,43 Due to 5 orders of magnitude difference between heating rates in our FSC experiments and those in traditional DSC experiments, tens of the degrees increase in T g is typical. 18,[44][45][46] As we explain immediately below, in the case of water, such a shift in T g toward higher values must facilitate greater sensitivity toward glass endotherms. In the case of benzene films, the lack of endo-and exotherms is due to C 6 H 6 crystallization during deposition.…”

Section: ' Experimental Sectionmentioning

confidence: 96%

Bulk and Interfacial Glass Transitions of Water

2011

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Fast scanning calorimetry (FSC) was employed to investigate glass softening dynamics in bulk-like and ultrathin glassy water films. Bulk-like water samples were prepared by vapor-deposition on the surface of a tungsten filament near 140 K where vapor-deposition results in low enthalpy glassy water films. The vapor-deposition approach was also used to grow multiple nanoscale (approximately 50 nm thick) water films alternated with benzene and methanoic films of similar dimensions. When heated from cryogenic temperatures, the ultrathin water films underwent a well manifested glass softening transition at temperatures 20 K below the onset of crystallization. However, no such transition was observed in bulk-like samples prior to their crystallization. These results indicate that thin-film water demonstrates glass softening dynamics that are dramatically distinct from those of the bulk phase. We attribute these differences to water's interfacial glass transition, which occurs at temperatures tens of degrees lower than that in the bulk. Implications of these findings for past studies of glass softening dynamics in various glassy water samples are discussed.

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Section: ' Experimental Sectionmentioning

confidence: 96%

Bulk and Interfacial Glass Transitions of Water

2011

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“…45 The samples have been deposited at substrate temperatures between 82 and 135 K, corresponding respectively to 0.70T g and 1.15T g , with T g = 117 K being the glass transition temperature of a conventional glass of toluene. 44 Specific heat curves of the samples deposited at 82.6 K, 104.0 K, 133.8 K and after passive cooling of the liquid (FC) have been obtained by dividing the heat capacity curves by the corresponding mass (left panels in Fig.…”

Section: Determination Of the Transformation Mechanismmentioning

confidence: 99%

“…45,46 Voltage raw data were converted into heat capacity curves following the procedure explained elsewhere. 47 A 100 nm aluminium plate was evaporated on the sensing area of the device in order to obtain a homogeneous thermal profile across the sample.…”

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confidence: 99%

The role of thermodynamic stability in the characteristics of the devitrification front of vapour-deposited glasses of toluene

Ràfols‐Ribé

González-Silveira

Rodríguez-Tinoco

et al. 2017

Phys. Chem. Chem. Phys.

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Physical vapour deposition (PVD) has settled in as an alternative method to prepare glasses with significantly enhanced properties, providing new insights into the understanding of glass transition. One of the striking properties of some PVD glasses is their transformation into liquid via a heterogeneous mechanism that initiates at surfaces/interfaces. Here, we use membrane-based fast-scanning nanocalorimetry (10 4 K s À1) to analyse the variables that govern the transformation mechanism of vapourdeposited toluene glasses with different stabilities. Thin films ranging from 20 to 250 nm were prepared at deposition temperatures between 0.70 and 1.15 times the glass transition temperature. We show how a propagating growth front is the initial transformation mechanism in all the vapour deposited samples, revealing a clear tendency to faster front velocities for less stable samples. Contrary to other glassformers such as indomethacin, toluene shows a one-to-one relationship between limiting fictive temperature and front velocity. We associate this behaviour with the much simpler molecular geometry of toluene, which would prevent the presence of strong preferential molecular arrangements in the glass. However, the propagation distance of the growth front before the homogenous transformation mechanism dominates the transition is found to be dependent on the preparation conditions rather than on the thermal stability of the glass. Understanding the link between the growth variables and the properties of PVD glasses is crucial for finding and developing potential applications of this type of glass.

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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%

“…Fortunately, an exciting method has been developed for preparing glass films that are close to equilibrium at temperatures considerably below the conventional T g (23)(24)(25)(26)(27). Recent work has shown that, when the correct substrate temperature and deposition rate are used, physical vapor deposition can produce amorphous samples with lower enthalpies (24) and higher densities (28) than glasses formed by cooling a liquid at a few degrees Kelvin per minute.…”

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confidence: 99%

Physical vapor deposition as a route to hidden amorphous states

Dawson

Kearns

et al. 2009

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

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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In situ nanocalorimetry of thin glassy organic films

Cited by 59 publications

References 22 publications

Bulk and Interfacial Glass Transitions of Water

Bulk and Interfacial Glass Transitions of Water

The role of thermodynamic stability in the characteristics of the devitrification front of vapour-deposited glasses of toluene

Physical vapor deposition as a route to hidden amorphous states

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