Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA.
J Phys Chem B. 2010 Mar 4;114(8):2635-43. doi: 10.1021/jp9107359.
Physical vapor deposition onto substrates near 0.85T(g) can prepare organic glasses with low enthalpy, high density, and high thermal stability. Isotopically labeled multilayer films of tris(naphthyl)benzene and indomethacin stable glasses were prepared and secondary ion mass spectrometry was used to study the evolution of these materials upon heating above T(g). In contrast to ordinary glasses, when stable glasses are held above T(g) they transform to a liquid via a growth front mechanism. In these experiments, growth fronts are initiated at the free surface of the glass and in some cases at the glass/substrate interface or an internal interface in the glass. For tris(naphthyl)benzene, the velocity of this growth front is observed to be nearly independent of the stability of the glass. Diffusion in the liquid that results from the growth front is initially 2-5 times faster than for the equilibrium supercooled liquid at the same temperature; the nature of this liquid is unclear. Under some circumstances, the slow evolution of this unusually mobile liquid into the equilibrium supercooled liquid can be observed.
在接近 0.85T(g) 的基底上进行物理气相沉积，可以制备低焓、高密度和高热稳定性的有机玻璃。我们制备了具有同位素标记的三（萘基）苯和吲哚美辛稳定玻璃的多层膜，并使用二次离子质谱研究了这些材料在 T(g)以上加热时的演变。与普通玻璃不同，当稳定玻璃保持在 T(g)以上时，它们通过生长前沿机制转变为液体。在这些实验中，生长前沿在玻璃的自由表面处开始，在某些情况下在玻璃/基底界面处或玻璃内部界面处开始。对于三（萘基）苯，观察到这个生长前沿的速度几乎与玻璃的稳定性无关。生长前沿导致的液体中的扩散最初比相同温度下平衡过冷液体快 2-5 倍；这种液体的性质尚不清楚。在某些情况下，可以观察到这种异常移动的液体缓慢演变成平衡过冷液体。
