Department of Chemistry, The George Washington University, Washington, DC 20052, USA.
J Phys Chem A. 2011 Jun 16;115(23):5965-72. doi: 10.1021/jp110372t. Epub 2011 Mar 14.
Fast scanning calorimetry (FSC) was employed to investigate glass softening dynamics in bulk-like and ultrathin glassy water films. Bulk-like water samples were prepared by vapor-deposition on the surface of a tungsten filament near 140 K where vapor-deposition results in low enthalpy glassy water films. The vapor-deposition approach was also used to grow multiple nanoscale (approximately 50 nm thick) water films alternated with benzene and methanoic films of similar dimensions. When heated from cryogenic temperatures, the ultrathin water films underwent a well manifested glass softening transition at temperatures 20 K below the onset of crystallization. However, no such transition was observed in bulk-like samples prior to their crystallization. These results indicate that thin-film water demonstrates glass softening dynamics that are dramatically distinct from those of the bulk phase. We attribute these differences to water's interfacial glass transition, which occurs at temperatures tens of degrees lower than that in the bulk. Implications of these findings for past studies of glass softening dynamics in various glassy water samples are discussed.
快速扫描量热法（FSC）被用于研究块状和超薄玻璃态水膜中的玻璃软化动力学。块状水样品是通过在接近 140 K 的钨丝表面蒸镀制备的，蒸镀导致低焓玻璃态水膜的形成。蒸镀方法还用于生长多个纳米级（约 50nm 厚）的水膜，与苯和甲酸膜交替排列，其尺寸相似。当从低温加热时，超薄水膜在结晶起始温度以下 20 K 的温度下经历了明显的玻璃软化转变。然而，在结晶之前，块状样品中没有观察到这种转变。这些结果表明，薄膜水的玻璃软化动力学与块状相的动力学明显不同。我们将这些差异归因于水的界面玻璃化转变，其发生温度比体相低数十度。这些发现对过去各种玻璃态水样品中玻璃软化动力学的研究具有重要意义。
