Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session X02: Molecular GlassesFocus Live
|
Hide Abstracts |
Sponsoring Units: DPOLY DSOFT DCP DMP Chair: Michael Tylinski , Wentworth Institute of Technology |
Friday, March 19, 2021 8:00AM - 8:36AM Live |
X02.00001: How does a glass become a supercooled liquid? Extreme conditions yield new perspectives Invited Speaker: Marta Gonzalez-Silveira Kinetic facilitation describes the idea that a mobile region in a glass or a liquid can induce the mobility of an adjacent region, which had initially lower mobility, and was not expected to rearrange under those conditions. This mechanism has been used to explain the transformation of ultrastable organic thin films. In this case, a supercooled liquid front forms on the more mobile regions of the films, i.e. surfaces and interfaces, and propagates across the film, consuming a glass that otherwise would have remained almost unchanged for a much longer period of time. To the date, this is the clearest example of kinetic facilitation as the mechanism controlling the transition of a glass. However, this same mechanism has been used to describe the bulk transformation of a very stable glass. It has been predicted theoretically and observed in simulations that the bulk transformation into the supercooled liquid glass of very stable glasses will start at regions of very low stability and these regions will grow transforming into the liquid the adjacent glass. For this mechanism to dominate the transformation it is necessary to have a big contrast in mobility between the different regions of the glass. This can be achieved either by preparing glasses of very high stability or by pushing the transition to high temperatures, where the contrast in mobility between glass and liquid will increase. The use of fast scanning nanocalorimetry allows us to shift the transition to high temperatures, reproducing the necessary conditions for observing this type of mechanism for the transformation of the glass, even for glasses which are not ultrastable. We present here experimental results on the bulk transformation of vapor deposited glasses of different stabilities, showing how the growth of these more mobile regions plays an important role in the softening process in all cases. |
Friday, March 19, 2021 8:36AM - 8:48AM Live |
X02.00002: On the Allowable or Forbidden Nature of Vapor-Deposited Glasses Zhe Wang, Mathieu Bauchy Vapor deposition can yield glasses that are more stable than those obtained by the traditional melt-quenching route. However, it remains unclear whether vapor-deposited glasses are "allowable" or "forbidden," that is, if they are equivalent to glasses formed by cooling extremely slowly a liquid or if they differ in nature from melt-quenched glasses. Here, based on reactive molecular dynamics simulation (MD) of silica glasses, we show that, under certain conditions, vapor-deposited glasses can indeed be more stable than melt-quenched glasses. Importantly, we demonstrate that the allowable or forbidden nature of vapor-deposited glasses depends on the temperature of the substrate and, in turn, is found to be encoded in their medium-range order structure. |
Friday, March 19, 2021 8:48AM - 9:00AM Live |
X02.00003: Glasses Denser than Supercooled Liquid Yi Jin, Aixi Zhang, Shivajee Govind, Sarah Wolf, Alex Moore, Ahmad Arabi Shamsabadi, Zahra Fakhraai When aged below the glass transition temperature, Tg, the density of a glass cannot exceed that of the metastable supercooled liquid (SCL) state, unless crystals are nucleated. The only exception is when another, high-density SCL (HD-SCL) states exists, with a density between that of the ordinary SCL and the crystal states. Experimentally, such HD-SCL states have not been observed in simple molecular liquids, either in aged or vapor-deposited stable glasses, even near their Kauzmann temperatures. Here, we report that thin vapor-deposited films of N,N'-diphenyl-N,N'-bis(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine (TPD) have densities that exceed their corresponding SCL density by as much as 3%. These glasses are also more isotropic than their thick film counterparts, and do not show any signs of crystallization. We demonstrate that these states are achieved at a range of thicknesses (25 – 55 nm) where thin films have large mobility gradients due to enhanced surface mobility, allowing them to access states that are not accessible in bulk liquids, due to kinetic barriers. We hypothesize that another HD-SCL state exists in TPD that has a liquid-liquid phase transition temperature below Tg and as such it has not been previously observed. |
Friday, March 19, 2021 9:00AM - 9:12AM Live |
X02.00004: Multiple glass transitions in Freon 113 vapor-deposited orientational glasses ANA VILA COSTA, Joan Ràfols Ribé, Marta Gonzalez-Silveira, Aitor Lopeandía, Josep Lluís Tamarit, Javier Rodríguez Viejo Plastic crystals are good model systems to study the glass transition because while presenting translational symmetry they also exhibit orientational disorder. In this work, we study the multiple transitions in Freon 133 (1,1,2-trichlorotrifluorethane) vapor-deposited films grown at deposition temperatures ranging from 50 to 120K, well above and below the glassy crystal to plastic crystal transition temperature (Tgr=72K). |
Friday, March 19, 2021 9:12AM - 9:24AM Live |
X02.00005: Stable polystyrene glasses through PVD and UV radiation Junjie Yin, Adam Raegen, James Forrest Compared to normal glass, stable glass possesses a molecular packing much closer to that of an “ideal glass”, and thus displays extraordinarily enhanced density and exceptional kinetic stability. Stable glass prepared through physical vapour deposition (PVD) has been extensively studied in the last decade, but the technique has been applied mostly on organic small molecules such as indomethacin. Recently we have employed PVD to make stable oligomeric glasses. In this study, we use them as a starting point and extend our capacity to make high molecular weight polystyrene stable glasses. We achieve this by crosslinking the stable oligomeric glasses through dehydrogenation reaction under ultraviolet (UV) radiation. The resulting stable glasses can have significantly higher molecular weight depending on the degree of crosslinking. As characterized by ellipsometry, such network polystyrene glasses exhibit stable glass behaviours including improved density and kinetic stability. |
Friday, March 19, 2021 9:24AM - 9:36AM Live |
X02.00006: Specific heat at low temperatures of ultrastable glasses of TPD Manuel Moratalla, Marta Rodriguez-Lopez, Cristian Rodriguez-Tinoco, Javier Rodriguez-Viejo, Rafael J. Jimenez-Rioboo, Miguel Ramos Glasses exhibit thermal, vibrational and acoustic properties at low temperatures anomalously different from those found in crystalline solids, and with a remarkable degree of universality [1]. |
Friday, March 19, 2021 9:36AM - 9:48AM Live |
X02.00007: Stability dependence of local elastic inhomogeneities of amorphous solids Alireza Shakerpoor, Elijah Flenner, Grzegorz Szamel There is a rich history of studies that suggest the vibrational and thermal anomalies in amorphous solids are linked to the local fluctuations in the elastic matrix of the amorphous medium. More recently numerical and experimental studies have shown a correlation between the vibrational properties and the stability of the medium. In this work, we studied the interplay between the stability and the fluctuations in the local elastic constants for a wide range of stabilities. We found that the variance of the local elastic constants becomes smaller with increasing stability. We also investigated the spatial correlations of the local elastic constants and determined that these constants have only very short range correlations. |
Friday, March 19, 2021 9:48AM - 10:00AM Live |
X02.00008: Strong elasticity anisotropy in molecular glasses Zuyuan Wang, Yu Cang, George Fytas, Camille Bishop, Mark Ediger Although glass is often considered isotropic, anisotropic glasses can be prepared by physical vapor deposition of rod-shaped organic molecules. Those glasses feature tunable molecular orientations and anisotropic properties that are beneficial for applications such as organic semiconductors. While the deposition-condition-dependent molecular orientation and the associated optical birefringence of molecular glasses have been investigated, little is known about their mechanical anisotropy, which, however, is needed for understanding their strength upon mechanical loading in packaging and application. In this work, we use micro-Brillouin light spectroscopy to determine the elastic stiffness tensors of three glass films of itraconazole vapor-deposited at substrate temperatures (Tsub) of 330, 315, and 290 K, respectively. The five independent elastic constants in each tensor demonstrate the strong influence of the molecular orientation on the elastic anisotropy. The in- and out-of-plane Young’s moduli of the high Tsub sample, which features a vertical molecular orientation, exhibit a record high anisotropy ratio of 2.1 among molecular systems. |
Friday, March 19, 2021 10:00AM - 10:12AM Live |
X02.00009: Improved Mechanical Properties of Organic Stable Glasses by Nanoindentation Sarah Wolf, Sage Fulco, Aixi Zhang, Yi Jin, Shivajee Govind, Haoqiang Zhao, Patrick J. Walsh, Kevin Turner, Zahra Fakhraai Glasses with stability over ordinary, liquid-quenched glasses can be formed by the process of physical vapor deposition using sufficiently slow deposition rates at appropriate temperatures. These stable glasses have been shown to exhibit several interesting features including higher density, lower enthalpy, and better kinetic stability over ordinary glasses. Properties are dependent on the substrate temperature during deposition, with temperatures near .85Tg (glass transition temperature) producing the most stable glasses. Given these exceptional properties, it is of interest to further investigate the properties of stable glasses, including consideration of mechanical properties such as hardness and modulus. Using a temperature gradient for high-throughput acquisition of data, and nanoindentation for investigation of mechanics, we find that accurate determination of these properties requires a careful approach due to surface detection error. We are able to correct for this while achieving consistent, reliable results. We show enhancement of mechanics in stable glasses, consistent with trends in density increase. This increase in mechanics holds across several small molecule organic glasses of varying chemical structure. |
Friday, March 19, 2021 10:12AM - 10:24AM Live |
X02.00010: The Role of Intramolecular Relaxation in the Stability, Optical Birefringence, and Structural Anisotropy of Vapor Deposited Glasses Aixi Zhang, Haoqiang Zhao, Sarah Wolf, Shivajee Govind, Yi Jin, Alex Moore, Robert Riggleman, Patrick J. Walsh, Zahra Fakhraai Stable glasses (SGs) made by physical vapor deposition are characterized by improved density and kinetic stability compared to liquid-quenched glasses. Additionally, SGs are usually shown to be optically birefringent and structurally anisotropic. However, the relationship between molecular structure and SG properties remains obscured. Here, we choose two molecules: α,α-A and α,α-Phen, which differ by a substituent, anthracenyl (A) versus phenanthrenyl (Phen), on the 3,5-di(naphthalen-1-yl)benzene moiety (diarylbenzene). The A–diarylbenzene bond presents a higher rotational barrier than the Phen–diarylbenzene bond, making α,α-A molecule more rigid than α,α-Phen. We examine the stability, optical birefringence, and packing anisotropy of SGs formed by the two molecules as a function of deposition temperature, using Ellipsometry and Grazing Incidence Wide Angle X-ray Scattering. It is observed that α,α-A SGs, compared to α,α-Phen SGs, are more birefringent, with a larger anisotropic "layering peak" in the direction perpendicular to the substrate. These effects can be attributed to the α,α-A molecule's rigidity, which reduces its range of enhanced mobility at the surface and its ability to effectively pack, resulting in the layering behavior. |
Friday, March 19, 2021 10:24AM - 10:36AM Live |
X02.00011: Influence of isomeric ratio on stable glass forming ability and secondary relaxations in vapor-deposited mixtures of cis/trans-decahydroisoquinoline Benjamin Kasting, Megan E Tracy, Jan Philipp Gabriel, Anthony Guiseppi-Elie, Ranko Richert, Mark Ediger While many organic molecules can form highly stable glasses using physical vapor deposition (PVD), the stable glass forming ability of co-deposited mixtures is a relatively unexplored area. Here, we use in situ AC nanocalorimetry and interdigitated electrode broadband dielectric spectroscopy to explore the effect of varying the ratio of cis/trans isomers in vapor-deposited glasses of decahydroisoquinoline (DHIQ). DHIQ is a structural analogue of decahydronaphthalene (decalin) with a carbon to nitrogen substitution endowing it with a much larger dipole moment than decalin. Glasses of varying kinetic stability were prepared based on preparation temperature and isomeric ratio. Stable glasses displayed lower amplitude secondary relaxations relative to liquid-cooled glasses. This work broadens the scope of stable glass forming mixtures that can be prepared by PVD, expanding upon our previous work on cis/trans-decalin mixtures. |
Friday, March 19, 2021 10:36AM - 10:48AM Live |
X02.00012: Ultrastable Polymer Glass Adam Raegen, Junjie Yin, Qi Zhou, James Forrest Stable glasses prepared by vapour deposition are an analogue of glassy materials aged for geological time scales. We report the preparation and characterization of stable glasses of polymers (polystyrene and poly (methyl methacrylate) prepared by physical vapour deposition. By controlling substrate temperature, deposition rate, polymerization index and polydispersity, we prepare and characterize a variety of stable polymer glasses. These materials display the kinetic stability, low fictive temperatures and high density characteristic of stable glasses. Extrapolation of measured transformation times between the stable and normal glass provides estimates of the relaxation times of the equilibrium supercooled liquid as much as 30 K below the glass transition temperature. We will also discuss the difference between local relaxations in normal and stable polymer glass as well as promising results making stable polymer network glass. |
Friday, March 19, 2021 10:48AM - 11:00AM Live |
X02.00013: Anisotropy and Anharmonicity in Polystyrene Stable Glass Adam Raegen, Qi Zhou, Junjie Yin, James Forrest We have used spectroscopic ellipsometry to characterize the anisotropy in stable polymer glasses prepared by physical vapour deposition. These measurements reveal birefringence values (as measured by the magnitude of in-plane versus out-of-plane refractive index) less than 0.002 in vapour deposited polystyrenes with N from 6-12, and with fictive temperatures between 10 and 35 K below the Tg values. We have measured the thermal expansivity of these stable glasses, and compared to ordinary rejuvenated glass. The thermal expansivity of the stable glasses is less than that of ordinary glass with a difference that increases as the fictive temperature Tf decreases. |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700