Ngai K L
CNR-IPCF, Dipartimento di Fisica, Largo Bruno Pontecorvo 3, I-56127, Pisa, Italy and Silesian Center for Education and Interdisciplinary Research, Institute of Physics, University of Silesia, 75 Pulku Piechoty 1A, 41-500 Chorzow, Poland.
Phys Rev E. 2020 Sep;102(3-1):032606. doi: 10.1103/PhysRevE.102.032606.
A hydrogen-bonding network or hydrogen-bonded cluster is formed in many hydrogen-bonded glass formers. It determines the dynamics of structural α relaxation and the Johari-Goldstein (JG) β relaxation because breaking of hydrogen bonds is the prerequisite. However, the networks and clusters can be substantially reduced or totally removed in the liquid state by high temperature accompanying the applied high pressure in experiments, and in the glassy state by hyperquenching the liquid under pressure. By confining the glass former in nanometer spaces, the extended network cannot form, and in addition the finite size effect limits the growth of the length scale of the α relaxation on lowering temperature. Any of these actions will modify the structure of the original hydrogen-bonded glass former, and also the intermolecular interaction governing the relaxation processes. Consequently the dynamics of the structural α relaxation and the JG β relaxation, as well as the relation between the two processes, are expected to change. An important advance in the study of the dynamics of glass-forming materials is the existence of the strong connection between the α relaxation and the JG β relaxation. In particular, the ratio of their relaxation times, t_{α}(T)/t_{β}(T), is quantitatively determined by the exponent of the Kohlrausch relaxation function of the α relaxation. This property is valid in hydrogen-bonded glass formers as well as in non-hydrogen-bonded glass formers. The interesting question is whether this property continues to hold after the hydrogen-bonded glass former has been modified by high temperature under high pressure, nanoconfinement, and hyperquenching under pressure. Remarkably, the answer is positive as concluded from the analyses of the data in several hydrogen-bonded glass formers reported in this paper. So far the main theoretical explanation of this property has been the coupling model.
在许多氢键型玻璃形成体中会形成氢键网络或氢键簇。它决定了结构α弛豫和乔哈里 - 戈尔茨坦（JG）β弛豫的动力学，因为氢键的断裂是其前提条件。然而，在实验中，伴随着施加的高压，高温会使液态下的网络和簇大幅减少或完全消失；在玻璃态下，通过在压力下对液体进行超快速淬火也会使其消失。通过将玻璃形成体限制在纳米空间中，扩展网络无法形成，此外有限尺寸效应限制了α弛豫长度尺度在降温时的增长。这些行为中的任何一种都会改变原始氢键型玻璃形成体的结构，以及控制弛豫过程的分子间相互作用。因此，预计结构α弛豫和JGβ弛豫的动力学以及这两个过程之间的关系都会发生变化。玻璃形成材料动力学研究中的一个重要进展是α弛豫和JGβ弛豫之间存在紧密联系。特别是，它们弛豫时间的比值tα(T)/tβ(T)由α弛豫的科尔劳施弛豫函数的指数定量确定。这一特性在氢键型玻璃形成体以及非氢键型玻璃形成体中均有效。有趣的问题是，在氢键型玻璃形成体经过高温高压、纳米限域和压力下的超快速淬火改性后，这一特性是否仍然成立。值得注意的是，从本文报道的几种氢键型玻璃形成体的数据分析得出的答案是肯定的。到目前为止，对这一特性的主要理论解释是耦合模型。
