Glass Transitions, Polyamorphic Transitions, and Chemical Order Freezing Transitions, in Liquids and Other Complex Systems

液体和其他复杂系统中的玻璃化转变、多晶型转变和化学有序冻结转变

• 批准号: 0455621
• 负责人: C. Austen Angell
• 金额: --
• 依托单位: Arizona State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-03-15 至 2009-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0455621&HistoricalAwards=false
• 关键词: Glass; Transitions; Polyamorphic; Chemical; Order

This project aims to study glasses that are formed on extremely short time scales by "hyperquenching." Developed over decades to vitrify "bad" glassformers, hyperquenching has never been systematically applied to explore the high temperature structure and properties of common glassformers. The possibility of examining features of glassforming liquids in the absence of smearing by vibrational excitation is a central goal for this study. Some key results were obtained in the previous grant period supporting the concept of topological defects as elementary excitations in glasses, and experiments needed to properly develop this idea will be performed. Hyperquenching of glassformers like zink chloride (ZnCl2) containing site sensitive probes like cyanide ion CN- will be performed. Hyperquenching of complex ion containing glassformers will permit the definition of the second fictive temperature described in a recent paper. Initiated in 2004 are new glasses obtained by (i) "pressure-tuning" and (ii) mechanical damage. Pressure-quenched and damage-formed glasses will be examined as analogs of hyperquenched glasses. In addition, it is shown how, in systems with additional complexity over the usual glassformer, hyperquenching can open the door to detailed study of the complex process. This may be (i) a liquid-liquid phase change that can be quenched-in before it happens, and then studied at leisure during reheating, or (ii) a molecular structure change, such as the folding of a protein, or the progress of some chemical ordering process. In each case the preliminary proof of principle is given. using papers published during the present grant period. In this proposal some new points of departure for the experimental study of glassformers are outlined and resources to bring them to fruition are requested. Previous work in this group was focussed on liquids in metastable equilibrium, or on the transition from liquid to glass and back to liquid using similar time scales for cooling and heating. The new approach was originally designed to permit greater overlap with computer simulation, but has now been recognized as a strategy for exploring supercooled liquid states, and glassy state dynamics, in its own right. It is also motivated by the information on the nature of traps on the energy landscape (both their energetics and vibrational dynamics) that can be obtained by interrogation of the hyperquenched glass.%%%Under NSF support this author has just contributed an article on fundamental aspects of the glassy state to a book on Pharmaceuticals "Freeze Drying of Pharmaceuticals" because many of today's drugs are now being preserved in the glassy state by the freeze drying process. One of the reasons for this choice is that vitreous materials dissolve much more rapidly (in the stomach for instance) than do their crystalline analogs. This work on the thermodynamics and dynamic properties of glasses is of fundamental importance to the development of drug processing. This project on separating physical from chemical effects of hyperquenching will provide valuable training to both graduate and undergraduate researchers.

该项目旨在研究在极短的时间尺度上通过“超淬火”形成的玻璃。几十年来，超淬火技术一直被用于玻璃化“坏”的玻璃形成体，但从未被系统地应用于探索普通玻璃形成体的高温结构和性能。玻璃形成液体的振动激发的情况下的拖尾检查功能的可能性是本研究的中心目标。在前一个资助期获得了一些关键结果，支持拓扑缺陷作为玻璃中的基本激发的概念，并将进行适当开发这一想法所需的实验。将进行玻璃形成剂如氯化锌（ZnCl 2）的超淬灭，所述玻璃形成剂含有位点敏感探针如氰化物离子CN-。超淬火的复杂离子含有玻璃形成将允许定义的第二假想温度在最近的论文中描述。2004年开始的是通过（i）“压力调谐”和（ii）机械损伤获得的新玻璃。压力淬火和损伤形成的玻璃将被视为超淬火玻璃的类似物。 此外，它示出了如何，在系统中具有额外的复杂性超过通常的玻璃形成，hyperquenching可以打开大门，详细研究的复杂过程。这可能是（i）液-液相变，可以在它发生之前被淬灭，然后在再加热期间休闲地研究，或者（ii）分子结构变化，例如蛋白质的折叠，或者一些化学排序过程的进展。在每一种情况下的初步证明的原则。使用本资助期内发表的论文。在这一建议中，概述了玻璃成型实验研究的一些新的出发点，并要求提供资源使其取得成果。这个小组以前的工作集中在亚稳平衡的液体上，或者在冷却和加热的时间尺度相似的情况下从液体到玻璃再回到液体的转变上。这种新方法最初的设计是为了与计算机模拟有更大的重叠，但现在已经被认为是探索过冷液态和玻璃态动力学的一种策略。它也是由关于能量景观上的陷阱的性质的信息（它们的能量学和振动动力学）所激发的，这些信息可以通过询问超淬火玻璃来获得。在美国国家科学基金会的支持下，这位作者刚刚为一本关于药物的书《药物的冷冻干燥》撰写了一篇关于玻璃态基本方面的文章，因为今天的许多药物都是通过冷冻干燥过程以玻璃态保存的。这种选择的原因之一是，玻璃体材料比它们的晶体类似物溶解得更快（例如在胃中）。玻璃的热力学和动力学性质的这项工作是至关重要的药物加工的发展。本计画将超淬灭的物理效应与化学效应分离，将为研究生与本科生的研究人员提供有价值的训练。