Journal ArticleDOI
Glassy Dynamics and Glass Transition in Nanometric Thin Layers of Polystyrene
Martin Tress,Michael Erber,Emmanuel Urandu Mapesa,Heiko Huth,Jan Müller,Anatoli Serghei,Christoph Schick,Klaus-Jochen Eichhorn,Brigitte Voit,Friedrich Kremer +9 more
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In this article, the authors combine dielectric spectroscopy, X-ray reflectometry, alternating current and differential scanning calorimetry (DSC) to study glassy dynamics and the glass transition in nanometric thin layers of polystyrene (PS) having widely varying molecular weights.Abstract:
Broadband dielectric spectroscopy (BDS), spectroscopic vis-ellipsometry (SE), X-ray reflectometry (XRR), and alternating current (ACC) as well as differential scanning calorimetry (DSC) are combined to study glassy dynamics and the glass transition in nanometric thin (≥5 nm) layers of polystyrene (PS) having widely varying molecular weights (27 500−8 090 000 g/mol). For the dielectric measurements two sample geometries are employed, the common technique using evaporated electrodes and a recently developed approach taking advantage of nanostructures as spacers. All applied methods deliver the concurring result that deviations from glassy dynamics and from the glass transition of the bulk do not exceed margins of ±3 K independent of the layer thickness and the molecular weight of the polymer under study. Our findings are discussed in the context of the highly controversial literature and prove that an appropriate sample preparation is of paramount importance.read more
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Perspective: Supercooled liquids and glasses
Mark Ediger,Peter Harrowell +1 more
TL;DR: The connections between amorphous structure, high frequency motions, molecular motion, structural relaxation, stability against crystallization, and material properties, and the interpretation of supercooled liquid and glass properties in terms of the potential energy landscape is explored.
Journal ArticleDOI
Dynamics near Free Surfaces and the Glass Transition in Thin Polymer Films: A View to the Future
Mark Ediger,James A. Forrest +1 more
TL;DR: In this article, the authors discuss recent experiments that directly measure mobility at or near the surface of glassy polymers and indicate that enhanced mobility near the free surface can exceed bulk mobility by several orders of magnitude and extend for several nanometers into the bulk polymer.
Journal ArticleDOI
A review of recent advances in thermophysical properties at the nanoscale: From solid state to colloids
Lin Qiu,Lin Qiu,Ning Zhu,Yanhui Feng,Efstathios E. Michaelides,Gaweł Żyła,Dengwei Jing,Xinxin Zhang,Pamela M. Norris,Christos N. Markides,Omid Mahian +10 more
TL;DR: In this paper, a review of recent advances in the measurement and modeling of thermophysical properties at the nanoscale (from the solid state to colloids) is presented, including thermal conductivity, dynamic viscosity, specific heat capacity, and density.
Journal ArticleDOI
Direct measurement of molecular motion in freestanding polystyrene thin films.
TL;DR: Temperature-ramping and isothermal anisotropy measurements reveal the existence of two subsets of probe molecules with different dynamics, which are interpreted as indicating the presence of a high-mobility layer at the film surface whose thickness is independent of polymer molecular weight and total film thickness.
Journal ArticleDOI
Glass transition of polymers in bulk, confined geometries, and near interfaces
TL;DR: This review introduces the reader to experimental methodologies, theories, and simulations of glassy polymer dynamics and vitrification, and focuses discussion specifically on local order, free volume, irreversible chain adsorption, the Debye-Waller factor of confined and confining media, chain rigidity, and the absolute value of the vitrification temperature.
References
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Journal ArticleDOI
On the Temperature Dependence of Cooperative Relaxation Properties in Glass‐Forming Liquids
Gerold Adam,Julian H. Gibbs +1 more
TL;DR: In this paper, a molecularkinetic theory was proposed to explain the temperature dependence of relaxation behavior in glass-forming liquids in terms of the temperature variation of the size of the cooperatively rearranging region.
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Surface Studies of Solids by Total Reflection of X-Rays
TL;DR: In this paper, the shape of the curve of reflected x-ray intensity vs glancing angle in the region of total reflection was analyzed to study certain structural properties of the mirror surface about 10 to several hundred angstroms deep.
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Die Abhängigkeit der Viscosität von der Temperatur bie unterkühlten Flüssigkeiten
G. Tammann,W. Hesse +1 more
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Relaxation processes in supercooled liquids
TL;DR: The characteristic features of alpha and beta relaxation in the supercooled state of non-network forming liquids and polymers are reviewed in this paper, where a crossover temperature Tc, located above the calorimetric glass transition temperature Tg, where the transport properties change from those typical for a strongly coupled liquid to those characteristic for a glass.