Surface Crystallization and Diffusion of Organic Glasses

有机玻璃的表面结晶和扩散

• 批准号: 1206724
• 负责人: Lian Yu
• 金额: $ 53.5万
• 依托单位: University of Wisconsin-Madison
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-05-15 至 2016-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1206724&HistoricalAwards=false
• 关键词: Surface; Crystallization; Diffusion; Organic; Glasses

TECHNICAL SUMMARY: With support from the Solid State and Materials Chemistry program, Lian Yu and his student coworkers at the University of Wisconsin - Madison will study Surface Crystallization and Diffusion of Organic Glasses (DMR 1206724). Glasses constitute an important class of solids produced by cooling liquids, condensing vapors, and evaporating solutions while avoiding crystallization. According to the current view that crystallization is controlled by diffusion, glasses should not crystallize readily. Yet many do crystallize, sometimes surprisingly fast. Recent work has discovered new modes of crystal growth that emerge as organic liquids are cooled to become glasses. This study seeks to understand one such process: fast crystal growth at the surface of organic glasses. The team will test the hypothesis that the phenomenon arises because of surface molecular mobility and the possibility for surface crystals to grow toward free space. They will determine how molecules are transported to support upward-lateral growth of surface crystals through real-time high-resolution microscopy. Surface diffusion coefficients will be measured for organic glasses to learn whether surface diffusion can sustain surface crystal growth. Experiments will be performed to determine the effect of glass aging on surface crystallization and diffusion, and how the fast growth of surface crystals is terminated as glasses are heated to become liquids. Polymer additives will be used to perturb crystallization and diffusion to understand their role in stabilizing organic glasses against crystallization. The team will study how the nature of surface mobility changes from hard inorganic solids to soft organic solids, from crystals to glasses, and from small-molecule glasses to polymer glasses.NON-TECHNICAL SUMMARY:The results of this research will benefit many areas of science and technology in which crystallization, glasses, and surfaces are important. Glasses are amorphous materials that combine solid-like mechanical stability and liquid-like spatial uniformity, making them ideal for many applications ranging from telecommunication to bio-preservation. Understanding glass crystallization will benefit the fabrication of glass ceramics and control of bio-mineralization, for which amorphous solids are key precursors. This research will improve the stability of organic glasses against crystallization and advance their applications in electronic and biomedical technologies. Pharmaceutical scientists will benefit from this knowledge as they develop amorphous formulations to deliver poorly soluble drugs. Poor solubility is limiting the development of many drugs that are beneficial and can significantly advance health care in the U.S. and developing countries. This project will provide rates of surface diffusion on organic materials, which are essential for understanding and controlling many technological processes - crystal growth, sintering, stability of thin films, and durability of nano-materials. Although extensive data exist for metals and semiconductors, the data are lacking for soft organic materials. Graduate and undergraduate students will benefit from the multi-disciplinary nature of this project, having significant exposure to crystals and glasses, high and low molecular weight organic materials, and both industrial and academic research labs. Personnel supported by this grant will work with UW-Madison's Pre-college Enrichment Opportunity Program for Learning Excellence (PEOPLE), which has a proven record of increasing the enrollment of minority and low-income high school students to colleges and universities. This program provides experiences that help students to become scientifically literate citizens and encourages them to consider careers in science and engineering.

技术摘要：在固态和材料化学项目的支持下，威斯康星大学麦迪逊分校的连宇和他的学生同事将研究有机玻璃的表面结晶和扩散(DMR 1206724)。玻璃是一类重要的固体，由冷却液体、冷凝蒸汽和蒸发溶液而产生，同时避免结晶。根据目前认为析晶受扩散控制的观点，玻璃不应轻易析晶。然而，许多人确实结晶了，有时速度快得令人惊讶。最近的工作发现了当有机液体冷却成玻璃时出现的新的晶体生长模式。这项研究试图了解一个这样的过程：有机玻璃表面的快速晶体生长。该团队将测试这一假设，即这种现象是由于表面分子的移动性以及表面晶体向自由空间生长的可能性造成的。他们将通过实时高分辨率显微镜确定分子是如何运输的，以支持表面晶体的向上横向生长。将测量有机玻璃的表面扩散系数，以了解表面扩散是否能够维持表面晶体的生长。将进行实验，以确定玻璃老化对表面结晶和扩散的影响，以及当玻璃被加热成为液体时，表面晶体的快速生长是如何终止的。聚合物添加剂将被用来扰乱析晶和扩散，以了解它们在稳定有机玻璃抗析晶方面的作用。该小组将研究表面迁移率的性质如何从硬无机固体到软有机固体，从晶体到玻璃，从小分子玻璃到聚合物玻璃。非技术摘要：这项研究的结果将使结晶、玻璃和表面重要的许多科学和技术领域受益。玻璃是一种非晶态材料，结合了类似固体的机械稳定性和类似液体的空间均匀性，使其成为从电信到生物保护的许多应用的理想选择。了解玻璃晶化将有助于微晶玻璃的制备和生物矿化的控制，而无定形固体是生物矿化的关键前体。这项研究将提高有机玻璃的抗结晶稳定性，并促进其在电子和生物医学技术中的应用。制药科学家将从这一知识中受益，因为他们开发了无定形配方来提供难于溶解的药物。较差的溶解性限制了许多有益的药物的开发，这些药物可以显著促进美国和发展中国家的医疗保健。该项目将提供有机材料的表面扩散速率，这对于理解和控制许多工艺过程至关重要--晶体生长、烧结、薄膜的稳定性和纳米材料的耐用性。尽管有大量的金属和半导体数据，但软有机材料的数据很少。研究生和本科生将从这个项目的多学科性质中受益，他们将大量接触水晶和玻璃、高和低分子有机材料，以及工业和学术研究实验室。这笔助学金支持的人员将与威斯康星大学麦迪逊分校的大学前卓越学习丰富机会计划(People)合作，该计划在增加少数族裔和低收入高中生进入学院和大学的招生方面有着良好的记录。该计划提供经验，帮助学生成为具有科学素养的公民，并鼓励他们考虑在科学和工程领域就业。