Probing Fluctuations and Nanoscale Dynamics in Glasses and Other Complex Materials

9877069 Israeloff在这项研究中，新的扫描探针显微镜（SPM）技术将用于测量有机玻璃，聚合物和其他材料的介电和粘弹性特性的波动作为频率，时间，字段和位置的函数。对玻璃中纳米尺度波动的直接研究可以提供导致非指数弛豫、发散弛豫时间和玻璃化转变的缩放的动态过程的详细图像。 这些调查将解决关键问题，如长度规模和性质的分子协同性，异质性的重要性和它的时间演变。 统计措施，表征玻璃协同性可以直接与模拟提供的。 介电波动也将被用来调查预测违反波动耗散定理（FDT）在宏观老化玻璃。 虽然从未在实验中观察到，这些非平衡FDT违规可能提供一种手段来探测平衡玻璃序参量，并强烈依赖于模型。 这些研究解决了非平衡统计力学中一个基本的未解决的问题，并测试了各种玻璃化转变模型。 研究生和博士后参与这些调查。% 这项研究涉及液体和聚合物如何冻结成无序固体的基本问题，即，眼镜 虽然在过去已经做了很多工作，这些问题，目前的技术采用扫描探针显微镜现在允许这样的研究进行近原子/分子水平。 以这种方式，人们发现，复杂材料的物理性质可以显着变化时，在近分子长度尺度探测。 这项研究站在当代凝聚态物理学领域之一的最前沿，预计将为我们理解复杂材料的行为做出重大贡献，从而为未来技术做出贡献。 这项研究为凝聚态物理和材料科学的新兴领域的研究生和博士后研究人员的培训提供了极好的机会，从而有助于在21世纪世纪创造一个专业的物理学家和材料科学家干部就业。 ***

9877069IsraeloffIn this research novel scanning probe microscopy (SPM) techniques will be used to measure the fluctuations in the dielectric and visco-elastic properties of organic glasses, polymers, and other materials as a function of frequency, time, field and position. The direct study of nano-scale fluctuations in glasses could provide a detailed picture of the dynamical processes leading to non-exponential relaxation, diverging relaxation times, and scaling at the glass transition. These investigations will address critical issues such as the length scale and nature of the molecular cooperativity, and the importance of heterogeneity and its time evolution. Statistical measures which characterize glassy cooperativity can be directly compared with those provided by simulations. Dielectric fluctuations will also be used to investigate predicted violations of the fluctuation-dissipation theorem (FDT) in macroscopic aging glasses. Although never observed in experiments, these non-equilibrium FDT violations may provide a means to probe the equilibrium glass order parameter, and are strongly model dependent. These researches address a fundamental unresolved issue in non-equilibrium statistical mechanics as well as test various glass transition models. Graduate students and postdocs participate in these investigations.%%% This research deals with fundamental problems of how liquids and polymers freeze into disordered solids, i.e., glasses. Though much work in the past has been done on these problems, present technology employing scanning probe microscopy now allow such studies to be performed on a near-atomic/molecular level. In this manner it was found that the physical properties of complex materials can vary dramatically when probed at near molecular length scales. This research stands at the forefront of one of the areas of contemporary condensed matter physics and is expected to make significant contributions to our understanding on the behavior of complex materials and thus to future technology. This research provides excellent opportunities for the training of graduate students and post doctoral research associates in an emerging area of condensed matter physics and materials science, and thereby contributes to the creation of an expert cadre of physicists and materials scientists for employment in the 21st Century. ***