CAREER: Impact of Nanoconfinement on Large-Scale Dynamics of Polymers

技术概述：聚合物在界面附近的动态行为对其在广泛的高科技应用中的性能至关重要。这项CAREER研究的目的是了解控制纳米聚合物在界面之间扩散的参数，并利用这些信息构建能够实现预测能力的理论。大块聚合物的扩散依赖于基本变量，如链长和温度，已经被很好地理解，这些信息将为纳米尺度上的扩散比较提供坚实的基础。在本研究中，将使用荧光技术研究纳米聚合物在良好控制的平面界面之间的扩散。活性聚合将用于合成具有低多分散性指数的聚合物，这些聚合物含有共价键，热稳定的荧光团，不影响薄膜的玻璃化转变。提出的研究计划旨在：1)确定由化学相同单元组成的简单聚合物（即均聚物）的扩散系数如何受到围合尺寸大小以及聚合物与围合界面之间相互作用的影响。2)通过改变主链刚度、链线性（支链或星形聚合物），以及在具有不同表面化学性质的界面之间以特定方式自组装的嵌段共聚物模型，确定链结构与界面扩散的基本机制之间的关系。3)发展理论，确定尺度关系，构建预测模型，提高设计高性能纳米结构材料的能力。非技术摘要：该项目的目的是研究当表面被与聚合物分子大小相当的距离分开时，聚合物分子平行于表面的运动。这种理解在各种技术应用中都很重要，例如硬盘润滑和微电子制造，以及细胞内的生物过程。例如，聚合物的某些性质可以通过将聚合物与粘土混合而得到改善；这项研究将有助于解释聚合物在混合过程中如何在单个粘土颗粒之间的空间中移动。该项目的总体结果将是更全面地了解控制表面附近和中间聚合物运动的因素，这将改善新先进材料的设计规则，并增强对聚合物物理的理解。为了补充这项研究，这个CAREER项目的推广和教育部分是为了恢复和扩大社会和各级学生对STEM职业的兴趣，特别是针对那些在经济地位、种族和性别方面代表多样性的人。CAREER奖将允许PI开发一个少数民族教学研究员项目，该项目将研究生同事与来自一级高中的少数民族教师配对，进行尖端研究并开发涉及现代聚合物材料问题的新高中课程。通过积极参与，研究生还将对当前数学、科学和工程教育问题以及这些学科职业的社会观点产生新的认识。此外，为了更广泛地接触K-12学生，PI和研究生同事将开发工程探险模块，并将其纳入探索UT，这是一个校园日的表演，展览，讲座和实践活动。这个活动是免费的，涉及来自德克萨斯州各地的公众和K-12学生，PI和研究生将通过实践演示进行互动，突出“为什么塑料会这样做”。

TECHNICAL SUMMARY:The dynamic behavior of polymers near interfaces is critical to performance in a broad range of high-technology applications. The objective of this CAREER research is to develop an understanding of the parameters controlling the diffusion of polymers nanoconfined between interfaces and to use this information to construct theories that enable predictive capabilities. The dependence of bulk polymer diffusion on fundamental variables, such as chain length and temperature, is well understood and this information will provide a strong foundation for comparison of diffusion at the nanoscale. In this research, the diffusion of polymers nanoconfined between well-controlled planar interfaces will be studied using fluorescence techniques. Living polymerizations will be used to synthesize polymers with low polydispersity indexes containing covalently-bound, thermally-stable fluorophores that do not affect the glass transition of the film. The proposed research program seeks to: 1) Determine how diffusion coefficients of simple polymers composed of chemically identical units (i.e. homopolymers) are affected by the size of the confining dimension and by interactions between the polymer and the confining interfaces. 2) Identify the relationships between chain architecture and the fundamental mechanisms of interfacial diffusion by varying backbone rigidity, chain linearity (branched or star polymers), and by employing model block copolymers that self-assemble in specific ways when confined between interfaces with differing surface chemistry. 3) Develop theories, ascertain scaling relationships and construct predictive models that enhance capabilities for designing high-performance nanostructured materials.NON-TECHNICAL SUMMARY:The objective of this project is to perform a study of polymer molecule movement parallel to surfaces when the surfaces are separated by a distance comparable to the size of the polymer molecule. This understanding is important in a variety of technological applications, such as hard drive lubrication and microelectronics manufacturing, and in biological processes within cells. For example, certain properties of polymers can be improved by mixing polymers with clay; this study will help explain how the polymer moves in spaces between individual clay particles during the mixing process. The overall result of this project will be a more comprehensive understanding of the factors that control polymer motion near and in-between surfaces which will improve design rules for new advanced materials and enhance the understanding of polymer physics. To complement the research, the outreach and educational component of this CAREER project is to revive and expand the interest of society and students at all levels in STEM careers, especially targeting those who represent diversity with respect to economic status, ethnicity and gender. The CAREER award will allow the PI to develop a Minority Teaching Fellows program that pairs graduate student colleagues with minority teachers from Title 1 high-schools to conduct cutting-edge research and develop new high-school curricula involving modern issues of polymeric materials. Through active participation, graduate students will also develop new appreciation for current issues of math, science and engineering education and societal viewpoints of careers in these disciplines. Additionally, to more broadly reach K-12 students, the PI and graduate student colleagues will develop Engineering Expeditions modules to be incorporated into Explore UT, an on campus day of performances, exhibits, lectures and hands-on activities. This event is free and involves a broad cross-section of the public and K-12 students from all over the State of Texas with whom the PI and graduate students will interact through hands-on demonstrations highlighting "why plastics do what they do".