Tg Changes, Surface Effects, and Dynamics in Nanoconfined Polymers

技术：限制和表面效应的基本问题，在纳米尺度上的材料行为，特别是玻璃化转变（Tg）和相关的动力学，将解决使用模型热固性材料局限于各种nanocomposing几何形状，包括自由站立和支持薄膜，棒，和球体。 表面和固有尺寸效应的相对贡献将系统地变化，因为作为纳米限制长度尺度的函数的表面积到体积的缩放对于不同的几何形状是不同的。 模型聚氰脲酸酯材料将被用于研究，因为它们允许退火的残余应力没有去湿或孔生长的问题，并允许自由站立，以及支持结构的简易合成。 交联密度的Tg抑郁症的影响将被检查，以测试最近的建议，即分子的刚度和大小的合作重排区域是重要的因素，用于确定的Tg变化的幅度。 玻璃化转变温度将使用差示扫描量热法（DSC）测量，作为冷却速率的函数，动态将使用准等温DSC测量线性动态比热的新方法来测量。非技术：薄膜和其他特殊几何形状中的聚合物的性质将通过各种实验技术在固态下进行研究。这项研究的结果对于从根本上理解纳米级行为和测试这种行为的最新假设非常重要。 此外，这些结果对电子和航空航天工业很重要，因为它们将有助于优化纳米电子，纳米光刻和纳米复合材料应用中的聚合物性能。 拟议的工作包括培训两名研究生和一名本科生研究员，从事涉及纳米级聚合物化学和物理学以及量热法的前沿研究。 道德操守培训将纳入对学生的培训。 PI在与少数民族学生和女学生合作方面有着良好的记录，同样将做出巨大努力，将代表性不足的学生纳入该项目。 外联活动将包括为TTU方案开发一个为期一周的聚合物模块，“科学-这是女孩的事”，供高中女生使用，并为TTU超级星期六科学方案开发四个两小时的模块，供四至六年级学生使用。

TECHNICAL:The fundamental question of confinement and surface effects on material behavior at the nanoscale, and in particular the glass transition (Tg) and related dynamics, will be addressed using a model thermosetting material confined to various nanoconfining geometries, including freely-standing and supported thin films, rods, and spheres. The relative contributions of surface and intrinsic size effects will be systematically varied since the scaling of the surface area to volume as a function of nanoconfinement length scale differs for different geometries. Model polycyanurate materials will be used in the study because they allow annealing of residual stresses without dewetting or hole growth problems and allow facile synthesis of both freely-standing, as well as supported structures. The effect of crosslink density on the Tg depression will be examined in order to test recent suggestions that molecular stiffness and size of the cooperatively rearranging regions are important factors for determining the magnitude of the Tg changes. The glass transition temperature will be measured using differential scanning calorimetry (DSC) as a function of cooling rate, and dynamics will be measured using a new method for measuring the linear dynamic specific heat using quasi-isothermal DSC.NON-TECHNICAL:The properties of polymers in thin films and other special geometries are going to be studied in the solid state by a variety of experimental techniques. The results of the research are important for a fundamental understanding of nanoscale behavior and to test recent hypotheses for this behavior. In addition, the results are important to electronic and aerospace industries since they will facilitate optimization of polymer properties in nanoelectronic, nanolithographic, and nanocomposite applications. The proposed work includes the training of two graduate students and an undergraduate researcher in cutting edge research involving polymer chemistry and physics at the nanoscale and calorimetry. Ethics training will be incorporated into the training of the students. The PI has a strong track record working with minority and female students, and a strong effort will similarly be made to include underrepresented students in this project. Outreach will include development of a one-week long polymer module for the TTU program, "Science - It's a Girl Thing," for girls in high school, and the development of four two-hour modules for the TTU Super Saturdays science program for 4th to 6th graders.