Regensburg 2016 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 51: Glasses (joint session CPP/DY, organized by DY)
CPP 51.4: Vortrag
Donnerstag, 10. März 2016, 10:30–10:45, H48
Glass transition and stable glass formation of carbon tetrachloride — •Yeong Zen Chua1, Michael Tylinski2, Mark D. Ediger2, and Christoph Schick1 — 1Institute of Physics, University of Rostock, Rostock 18051 Germany — 2Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706 USA
There have been attempts to find correlations between the ability to form stable glasses and general characteristic of the materials. It was argued that asymmetric molecules, which allow anisotropic packing on the surface during deposition, are a prerequisite for stable glass formation. This leads to the question whether symmetric molecules can form stable glasses. Carbon tetrachloride (CCl4) is an ideal molecule to verify this hypothesis, since the molecule is pseudo spherical with no orientation. On the other side, the formation of stable glasses is thought to be mediated by a highly mobile surface layer. So it might be expected that CCl4, as a small and simple organic molecule, has enhanced mobile surface layer and thus increases its ability to form stable glasses. These conflicting factors lead to our investigation of CCl4 glasses produced by physical vapor deposition with insitu AC chip nanocalorimetry. Kinetically stable glasses have been observed to form at substrate temperature around 0.8 Tg, consistent with previous work on stable glass formers. The isothermal transformation of the as-deposited glasses into supercooled liquid state gave further evidence to support the stable glass formation, thus disproving molecular asymmetry as a prerequisite. The glass transition temperature is determined as Tg = (78±2) K, which is different from previously reported values.