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Karl Freed教授报告(2012-06-02)

( 2012-06-01 )
 

报告题目:The Descent into Glass-Formation

报告时间:2012年6月2日下午 2:30

报告地点:理化大楼一楼科技展厅

报告人:Professor Karl Freed,Chemistry Department,University of Chicago

报告人简介:

 

Karl F. Freed教授出生于1942年,于1963年获得哥伦比亚大学理学学士学位,于1965年、1967年分别获得哈佛大学文学硕士学位和博士学位。1968年Karl F. Freed在美国芝加哥大学化学系、杰姆斯·富兰克研究所任助理教授,于1973年升任副教授,1976年升任教授。Karl F. Freed教授曾于1983-1986年任杰姆斯·富兰克研究所所长,曾担任Chemical Reviews, Chemical Physics等学术期刊的顾问编辑,目前是J. Chem. Phys.的副主编。

 

报告摘要:

Glassy materials have been fundamental to technology since the dawn of civilization and remain so to this day: novel glassy systems are currently being developed for applications in energy storage, electronics, food, drugs, and more. Glass-forming fluids exhibit a universal set of transitions beginning at temperatures often in excess of twice the glass transition temperature Tg and extending down to Tg, below which relaxation becomes so slow that systems no longer equilibrate on experimental time scales. Despite the technological importance of glasses, no prior theory explains this universal behavior nor describes the huge variations in the properties of glass-forming fluids that result from differences in molecular structure. Not surprisingly, the glass transition is currently regarded by many as the deepest unsolved problem in solid state theory. We describe our recently developed theory of glass formation in polymer fluids. Our theory explains the origin of four universal characteristic temperatures of glass formation and their dependence on monomer-monomer van der Waals energies, conformational energies, and pressure and, perhaps most importantly, on molecular details, such as monomer structure, molecular weight, size of side groups, and so forth. The theory also provides a molecular explanation for fragility, a parameter that quantifies the rate of change with temperature of the viscosity and other dynamic mechanical properties at Tg. The fragility reflects the fluid's thermal sensitivity and determines the manner in which glass-formers can be processed, such as by extrusion, casting, or inkjet spotting.

 
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