Glasses and other non-crystalline solids exhibit thermal acoustic properties at low temperatures anomalously different from those found in crystalline solids, with a remarkable degree of universality. Below few K, these universal have been successfully interpreted using the Tunneling Model, which has enjoyed (almost) unanimous recognition for decades. Here we present low-temperature specific-heat measurements ultrastable glasses indomethacin that clearly show disappearance ubiquitous linear...

The rate at which a nonequilibrium system decreases its free energy is commonly ascribed to molecular relaxation processes, arising from spontaneous rearrangements the microscopic scale. While equilibration of liquids usually requires density fluctuations time scales quickly diverging upon cooling, growing experimental evidence indicates presence different, alternative pathway weaker temperature dependence. Such processes exhibit temperature-invariant activation energy, on order 100 kJ...

Abstract Ultrastable glasses (mostly prepared from the vapor phase under optimized deposition conditions) represent a unique class of materials with low enthalpies and high kinetic stabilities. These highly stable dense show physicochemical properties, such as thermal stability, improved mechanical properties or anomalous transitions into supercooled liquid, offering unprecedented opportunities to understand many aspects glassy state. Their respect liquid-cooled also open new prospects their...

Ultrastable thin film glasses transform into supercooled liquid via propagating fronts starting from the surface and/or interfaces. In this paper, we analyze consequences of mechanism in interpretation specific heat curves ultrastable indomethacin for samples with varying thickness 20 nm up to several microns. We demonstrate that films above have identical fictive temperatures and apparent change onset temperature originates transformation normalization procedure. An ad hoc capacity yields...

We show that the segmental mobility of thin films poly(4-chlorostyrene) prepared under nonequilibrium conditions gets enhanced in proximity rough substrates. This trend is contrast to existing treatments roughness which conclude it a source slower dynamics, and measurements poly(2-vinylpiridine), whose dynamics invariant. Our experimental evidence indicates faster interfacial originate from reduction density, due noncomplete filling substrate asperities. Importantly, our results agree with...

While ordinary glasses transform into supercooled liquid via a homogeneous bulk mechanism, thin film of higher stability heterogeneously by front propagating from the surface and/or interfaces. In this work, we use quasi-adiabatic fast scanning nanocalorimetry to determine heat capacity glassy layers indomethacin vapor-deposited in broad temperature range 110 K below glass transition temperature. Their variation fictive amounts 40 K. We show that is initial transformation mechanism all...

Glasses are out-of-equilibrium systems aging under the crystallization threat. During ordinary glass formation, atomic diffusion slows down, rendering its experimental investigation impractically long, to extent that a timescale divergence is taken for granted by many. We circumvent these limitations here, taking advantage of wide family glasses rapidly obtained physical vapor deposition directly into solid state, endowed with different "ages" rivaling those reached standard cooling and...

The understanding of glassy dynamics above the devitrification temperature a glass remains poorly understood. Here, we use real-time AFM imaging to build spatio-temporal map relaxation highly stable into its supercooled liquid. This new methodology enables direct visualization progression liquid phase and clarifies quantifies presence localized fast mobility regions separated by giant length scales. Our data permit establish clear correlation between dynamic time scales in glasses. approach...

Vapor-deposited organic semiconductor glasses exhibit distinct molecular anisotropy and exceptional kinetic thermodynamic stability, distinguishing them from the inherently isotropic poorly stable formed through liquid cooling. In this study, we exploit these unique properties to examine local changes in surface potential as glass transitions a supercooled upon heating above transition temperature (Tg). Vapor deposited of molecules with permanent dipole moments can generate measurable due...

We report the thermodynamic measurement of enthalpy released during aging supported films a molecular glass former, toluene, at temperatures well below transition temperature. By using microfabricated devices with very short equilibration times (below 1 s), we evidence remarkable variation relaxation rate on decreasing film thickness from 100 nm down to 7 thick film. Our results demonstrate that surface atoms are more efficient than bulk in attaining low energy configurations within...

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 striking properties some PVD is their transformation liquid via a heterogeneous mechanism that initiates at surfaces/interfaces. Here, we use membrane-based fast-scanning nanocalorimetry (104 K s-1) analyse variables govern vapour-deposited toluene different stabilities. Thin films ranging...

Nanocalorimetry at ultrafast heating rates is used to investigate the glass transition of nanometer thick films metastable amorphous solid water grown by vapor deposition in an ultrahigh vacuum environment. Apparent heat capacity curves exhibit characteristic features depending on temperature. While T ≥ 155 K are completely crystallized, those deposited 90 show a relaxation exotherm prior crystallization. Films between 135 and 140 subsequently cooled down reveal clear endothermic feature...

Abstract While lots of measurements describe the relaxation dynamics liquid state, experimental data glass at high temperatures are much scarcer. We use ultrafast scanning calorimetry to expand timescales shorter values than previously achieved. Our show that time glasses follows a super-Arrhenius behaviour in high-temperature regime above conventional devitrification temperature heating 10 K/min. The and states can be described by common VFT-like expression solely depends on limiting...

Secondary relaxations persistent in the glassy state after structural arrest are especially relevant for properties of glass. A major thrust research dynamics glass-forming liquids is to identify what secondary exhibit a connection relaxation and hence more relevant. Via Coupling Model, having such have been identified by similar primitive Model called Johari-Goldstein (JG) β-relaxations. They involve motion entire molecule act as precursor α-relaxation. The change aging an ordinary glass...

Physical vapour deposition has emerged as the technique to obtain glasses of unbeatable stability. However, deposited exhibit a different transformation mechanism ordinary produced from liquid. Vapour thermodynamic stability, ultrastable those similar glasses, transform into liquid state via front propagation starting at most mobile surfaces/interfaces, least for first stages transformation, eventually dynamiting high thermal stability achieved some these glasses. A previous study showed...

Thin film stable glasses transform into a liquid by moving front that propagates from surfaces or interfaces with higher mobility. We use calorimetric data of vapor-deposited different thicknesses and stabilities to identify the role glassy dynamics on transformation process. By invoking existence an ultrathin intermediate layer whose strongly depends properties both glass, we show recovery equilibrium is driven mismatch in between glass liquid. The lifetime this associated geometric mean...

Secondary relaxations are fundamental for their impact in the properties of glasses and inseparable connection to structural relaxation. Understanding density dependence aging behavior is key fully address nature glasses. Ultrastable establish a new benchmark study characteristics secondary relaxations, since enthalpy levels unattainable by other routes. Here, we use dielectric spectroscopy at ambient elevated pressures relaxation ultrastable etoricoxib, reporting 71% decrease strength one...

The manipulation of molecular orientation is a well established target in organic electronics and energy-harvesting applications since it may affect relevant parameters such as energy levels, electron transport, exciton recombination...

The primitive/JG relaxation explains the same surface diffusion coefficient in ordinary, ultrastable and thin film glasses of OTP TPD.

The translational diffusion of molecules dispersed into polymer matrices slows down tremendously when approaching a nonrepulsive interface. To unravel the origin this phenomenon, we investigated molecular probes in direction normal to an adsorbing wall. Using adsorbed layers as matrices, were able decouple interfacial and finite size effects determined relation between time area available at polymer/solid Based on results our investigation, present physical picture, suggesting that reduction...

Pressure experiments provide a unique opportunity to unravel new insights into glass-forming liquids by exploring its effect on the dynamics of viscous and evolution glass transition temperature. Here we compare pressure dependence onset devitrification, Ton, between two molecular glasses prepared from same material but with extremely different ambient-pressure kinetic thermodynamic stabilities. Our data clearly reveal that, while both exhibit dTon/dP values at low pressures, they evolve...

Coupling-Model-based theoretical explanation of the minor change JG β-relaxation achieved by ultrastability in contrast to dramatic α-relaxation.

Abstract The high frequency dynamics of Indomethacin and Celecoxib glasses has been investigated by inelastic x-ray scattering, accessing a momentum-energy region still unexplored in amorphous pharmaceuticals. We find evidence phonon-like acoustic determine the THz behavior sound velocity attenuation. Connections with ordinary propagation are discussed, along relation between fast slow degrees freedom as represented non-ergodicity factor kinetic fragility, respectively.