PECASE: Nanoscale Confinement in Polymers: Integrated Research and Education in Nanoscale Experimental Mechanics

该学院早期职业发展(CALEAR)课程旨在量化聚合物在纳米尺度限制和硬表面附近限制/增强的大分子迁移率下的机械行为。后者将被设计成模拟聚合物纳米复合材料中接近原始和功能化的纳米管和纳米纤维的聚合物分子的行为。在这些材料体系中，大的表面积体积比使得硬质相限制了分子的流动性和构象。因此，整个复合材料实际上可能是一个界面，具有与原始本体聚合物非常不同的局部和有效的宏观性质。将开发实验纳米级探针方法，以确定纳米级分子耗散的变化，并量化超薄聚合物薄膜中表面分子的集体时间相关响应。测量粘弹性蠕变函数和玻璃化转变温度随聚合物层厚度的变化将为评估硬界面附近的分子构象提供数据。由于缺乏关于硬表面附近聚合物基质改性的局部信息，制备强韧、多功能和轻质聚合物纳米复合材料的潜力远远达不到其预期的潜力。如果成功，该计划将为高性能纳米结构聚合物的受控和高效设计奠定基础，并建立多相聚合物的性能限制。该计划的实验结果将是分子动力学和微力学模型的基本材料参数，应用于纳米复合材料、生物系统、纳米印迹、纳米流体阵列等。该职业奖项的外展计划将(A)通过工程教学套件激励高中生学习航空航天工程，该教材将提高高中生对航空航天应用的分层材料的技术意识，(B)向本科生和研究生提供纳米力学实践教育，以及(C)支持专业人员进行纳米力学实验室培训。

This Faculty Early Career Development (CAREER) program seeks to quantify the mechanical behavior of polymers subjected to nanoscale confinement and restricted/enhanced macromolecular mobility near hard surfaces. The latter will be designed to simulate the behavior of polymer molecules near pristine and functionalized nanotubes and nanofibers in polymer nanocomposites. The large surface-to-volume ratio in these material systems is such that the hard phase restricts molecular mobility and conformations. As a result, the entire composite may be practically an interphase, with local and effective macroscopic properties being very different from pristine bulk polymers. Experimental nanoscale probe methods will be developed to determine variations in molecular dissipation at the nanoscale and to quantify the collective time-dependent response of surface molecules in ultra-thin polymer films. Measurements of the viscoelastic creep functions and glass transition temperatures as a function of polymer layer thickness will provide the data to assess molecular conformations near hard interfaces.Due to the lack of local information on polymer matrix modification near hard surfaces, the fabrication of strong and tough multifunctional and lightweight polymeric nanocomposites is far from reaching its projected potential. If successful, this program will set the foundations for controlled and efficient design of high performance nanostructured polymers and establish property limits for multiphase polymers. The experimental results from this program will be essential material parameters for molecular dynamics and micromechanics models with applications to nanocomposites, biological systems, nanoimprinting, nanofluidic arrays, etc. The outreach plan of this CAREER award will (a) inspire high school students to study aerospace engineering via an engineering teaching kit that will increase high school student technology awareness in hierarchical materials for aerospace applications, (b) provide hands-on education on nanoscale mechanics to undergraduate and graduate students, and (c) support professionals with nanoscale mechanics laboratory training.