Whitaker Katherine R, Tylinski M, Ahrenberg Mathias, Schick Christoph, Ediger M D
Department of Mathematics and Physical Sciences, Louisiana State University of Alexandria, Alexandria, Louisiana 71302, USA.
Department of Chemistry, University of Wisconsin - Madison, Madison, Wisconsin 53706, USA.
J Chem Phys. 2015 Aug 28;143(8):084511. doi: 10.1063/1.4929511.
The reversing heat capacity of vapor-deposited o-terphenyl glasses was determined by in situ alternating current nanocalorimetry. Glasses were deposited at substrate temperatures ranging from 0.39 Tg to Tg, where Tg is the glass transition temperature. Glasses deposited near 0.85 Tg exhibited very high kinetic stability; a 460 nm film required ∼10(4.8) times the structural relaxation time of the equilibrium supercooled liquid to transform into the liquid state. For the most stable o-terphenyl glasses, the heat capacity was lower than that of the ordinary liquid-cooled glass by (1 ± 0.4)%; this decrease represents half of the difference in heat capacity between the ordinary glass and crystal. Vapor-deposited o-terphenyl glasses exhibit greater kinetic stability than vapor-deposited glasses of indomethacin, in qualitative agreement with recent surface diffusion measurements indicating faster surface diffusion on o-terphenyl glasses. The stable glass to supercooled liquid transformation was thickness-dependent, consistent with transformation via a propagating front initiated at the free surface.
通过原位交流纳米量热法测定了气相沉积邻三联苯玻璃的可逆热容量。玻璃在0.39Tg至Tg的基板温度下沉积，其中Tg是玻璃化转变温度。在0.85Tg附近沉积的玻璃表现出非常高的动力学稳定性；一个460nm的薄膜需要平衡过冷液体结构弛豫时间的约10^(4.8)倍才能转变为液态。对于最稳定的邻三联苯玻璃，其热容量比普通液冷玻璃低(1±0.4)%；这种降低代表了普通玻璃和晶体之间热容量差异的一半。气相沉积的邻三联苯玻璃比气相沉积的吲哚美辛玻璃表现出更高的动力学稳定性，这与最近的表面扩散测量结果定性一致，该测量结果表明邻三联苯玻璃上的表面扩散更快。稳定玻璃到过冷液体的转变与厚度有关，这与在自由表面引发的传播前沿的转变一致。
