Peter A. Rock Thermochemistry Laboratory and NEAT ORU, University of California at Davis, Davis, California 95616, USA.
J Phys Chem B. 2010 Mar 4;114(8):3070-4. doi: 10.1021/jp911821p.
The dynamics of glass-forming liquids under nanoconfinement is key to understanding a variety of phenomena in nature and modern technology. We report a (13)C NMR spectroscopic study that directly demonstrates that alpha-relaxation in bulk glycerol involves an isotropic rotational jump of the constituent molecules. The activation energy of this motion is approximately 78 kJ mol(-1) in the bulk, which abruptly changes to a low value of approximately 27.5 kJ mol(-1), characteristic of beta-processes, upon confinement of glycerol into approximately 2 nm pores in mesoporous silica. This observation implies that the molecular dynamics associated with structural relaxation near glass transition are inherently different in supercooled glycerol in the bulk and under extreme nanoconfinement.
纳米受限条件下玻璃形成液体的动力学对于理解自然界和现代技术中的各种现象至关重要。我们报告了一项（13）C NMR 光谱研究，该研究直接证明了在块状甘油中，α松弛涉及组成分子的各向同性旋转跳跃。在块状甘油中，这种运动的活化能约为 78 kJ mol(-1)，而当甘油被限制在介孔二氧化硅中约 2nm 的孔中时，它会突然变为约 27.5 kJ mol(-1)，这是β过程的特征。这一观察结果表明，在过冷甘油的本体和极端纳米受限条件下，与玻璃化转变附近结构弛豫相关的分子动力学本质上是不同的。
