NIRT: Dynamic Heterogeneity and the Behavior of Glass-Forming Materials at the Nanoscale

该NIRT奖由材料研究部的聚合物项目和化学与传输系统部的界面、传输和热力学项目资助。这项工作旨在了解聚合物和小分子玻璃形成物的空间动态异质性如何受到纳米尺度限制的影响，以及这反过来如何影响分子和热力学性质的弛缓。动态非均质性将通过荧光探针研究和纳米受限材料的溶剂化动力学作为约束尺寸的函数进行系统探索。此外，体积和焓弛豫将作为约束的函数来研究，其具体目的是检查动态非均质性是否影响这些性质的弛豫，以及它是否是达到平衡所需的时间发散的原因。纳米约束将包括交联橡胶中低分子量玻璃形成物的“软”约束，纳米多孔基质中低分子量玻璃形成物和聚苯乙烯的“刚性”约束，以及聚苯乙烯对超薄膜的约束。此外，还研究了冻干聚苯乙烯玻璃的宏观和分子弛豫行为。这项工作将包括许多以前没有进行过的新测量，预计将导致对约束如何影响动态非均质性的理解，以及更一般地说，动态非均质性对Tg附近宏观性质松弛的重要性。这项工作将更好地理解材料在玻璃温度附近的行为，在中微米或纳米尺度上，对于材料的最终用途和功能非常重要，例如，纳米复合材料和纳米电子应用。该项目还将为研究生、博士后研究人员和高中生提供优秀的培训。将努力将本科生和高中生纳入研究对象。将通过在德克萨斯州和西南地区的女子和少数民族学院的特别招生工作，努力将妇女和代表性不足的少数民族纳入其中。此外，将努力包括参加TTU麦克奈尔学者计划的第一代大学生（通常是少数民族）的本科生。这项工作将在科学界广泛传播，在国家论坛上发表，并在会议论文集和档案期刊上发表。该项目的研究结果亦会在可行的情况下，纳入由有关私家学院教授的本科及研究生课程***

This NIRT award is being funded by the Polymers Program of the Division of Materials Research and the Interfacial, Transport and Thermodynamics Program of the Division of Chemical and Transport Systems. The work is aimed at understanding how spatially dynamic heterogeneity in polymeric and small molecule glass formers is influenced by confinement at the nanoscale, and how this in turn, influences the relaxation of molecular and thermodynamic properties. Dynamic heterogeneity will be systematically probed using fluorescent probe studies and solvation dynamics in nanoconfined materials as a function of confinement size. In addition, volume and enthalpy relaxation will be studied as a function of confinement with the specific aim of examining whether or not dynamic heterogeneity influences the relaxation of these properties and whether or not it is the cause of the divergence of times required to reach equilibrium. Nanoconfinement will include "soft" confinement of low molecular weight glass-formers in crosslinked rubber, "rigid" confinement of both low molecular weight glass-formers and polystyrene in nanoporous matrices, and confinement of polystyrene to ultrathin films. In addition, the macroscopic and molecular relaxation behavior of freeze-dried polystyrene glasses will be examined. The work will include many novel measurements that have not been performed previously and is anticipated to lead to an understanding of how dynamic heterogeneity is influenced by confinement, and more generally, the importance of dynamic heterogeneity on the relaxation of macroscopic properties near Tg.%%%The work will provide a better understanding of the behavior of materials near their glass temperatures at the meso- or nanometer scale and is important for the ultimate usefulness and function of materials in, for example, nanocomposites and nanoelectronics applications. The program will also provide excellent training for the graduate students and post-doctoral researchers and high school students. Efforts will be made to include undergraduate researchers and high school students. Efforts will be made to include women and underrepresented minorities through special recruiting efforts at women's and minority colleges in the Texas and southwest region. In addition, an effort will be made to include undergraduate students who participate in the TTU McNair Scholars Program for first generation college students (often minorities). The work will be broadly disseminated within the scientific community by presentation at national forums and publication in both proceedings conferences and archival journals. The results of the project will also be incorporated to the extent feasible in both undergraduate and graduate courses taught by the respective PIs.***