Chua Y Z, Tylinski M, Tatsumi S, Ediger M D, Schick C
Institute of Physics, University of Rostock, Albert-Einstein-Str. 23-24, 18059 Rostock, Germany.
Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA.
J Chem Phys. 2016 Jun 28;144(24):244503. doi: 10.1063/1.4954665.
Physical vapor deposition (PVD) has been used to prepare organic glasses with very high kinetic stability and it has been suggested that molecular anisotropy is a prerequisite for stable glass formation. Here we use PVD to prepare glasses of tetrachloromethane, a simple organic molecule with a nearly isotropic molecular structure. In situ AC nanocalorimetry was used to characterize the vapor-deposited glasses. Glasses of high kinetic stability were produced by deposition near 0.8 Tg. The isothermal transformation of the vapor-deposited glasses into the supercooled liquid state gave further evidence that tetrachloromethane forms glasses with high kinetic stability, with the transformation time exceeding the structural relaxation time of the supercooled liquid by a factor of 10(3). The glass transition temperature of liquid-cooled tetrachloromethane is determined as Tg ≈ 78 K, which is different from previously reported values. The frequency dependence of the glass transition was also determined and the fragility was estimated as m ≈ 118. The successful formation of PVD glasses of tetrachloromethane which have high kinetic stability argues that molecular asymmetry is not a prerequisite for stable glass formation.
物理气相沉积（PVD）已被用于制备具有非常高动力学稳定性的有机玻璃，并且有人提出分子各向异性是形成稳定玻璃的先决条件。在此，我们使用PVD制备四氯化碳玻璃，四氯化碳是一种具有近乎各向同性分子结构的简单有机分子。采用原位交流纳米量热法对气相沉积玻璃进行表征。通过在接近0.8 Tg的温度下沉积制备出具有高动力学稳定性的玻璃。气相沉积玻璃等温转变为过冷液态进一步证明了四氯化碳能形成具有高动力学稳定性的玻璃，其转变时间比过冷液体的结构弛豫时间长10³倍。测定了液冷四氯化碳的玻璃化转变温度为Tg≈78 K，这与先前报道的值不同。还确定了玻璃化转变的频率依赖性，并估计其脆性为m≈118。成功制备出具有高动力学稳定性的四氯化碳PVD玻璃表明，分子不对称性并非形成稳定玻璃的先决条件。
