Understanding and Exploiting the Transport Behavior of Polymers in Confined Geometries

目前，在从根本上理解聚合物在受限几何（如超薄膜）中的热力学和输运性质，以及这些性质对薄膜厚度和制备条件的依赖方面，存在着重大的知识空白。最近的研究表明，当薄膜厚度低于某一临界厚度时，各种聚合物薄膜的性能都偏离了体行为。我们最近的测量表明，渗透剂通过聚合物超薄膜的体积扩散随着薄膜厚度的减少而急剧下降，而聚合物薄膜的质子电导率似乎没有以类似的方式下降。这项工作的首要目标是表征聚合物在受限几何中的质子传输和扩散行为，阐明这种行为的长度尺度和大小，并对导致观察到的现象的机制形成自一致和全面的基本理解。该提案的智力优点可以大致定义为：(1)表征聚合物超薄膜中的质子传输，(2)开发一个基本模型来解释聚合物超薄膜的物理化学性质，以及(3)利用观察到的行为来提高使用现有材料和工艺的燃料电池质子交换膜的能力。这项活动的广泛影响包括：(1)为克服微光刻技术中的一些障碍提供指导和机会，使微电子工业受益；(2)提供一种提高燃料电池聚合物膜性能的方法；(3)以一种协同混合建模和实验的方式教育本科生和研究生；(4)加强代表性不足和少数民族学生的教育，并改善中学科学教育。

Currently there are significant knowledge gaps in fundamentally understanding the thermodynamic and transport properties of polymers in confined geometries (e.g. ultra-thin films), and the dependence of these properties on film thickness and preparation conditions. Recent studies have shown that a wide variety of polymer film properties deviate from bulk behavior as the film thickness decreases below some critical thickness. Our recent measurements suggest that bulk diffusion of penetrants through polymer ultra-thin films decreases dramatically with decreasing film thickness while the proton conductivity of polymer films does not appear to decrease in a similar manner. The overarching goals of this work are to characterize the proton transport and diffusion behavior of polymers in confined geometries, elucidate the length scales and magnitudes of such behavior, and develop a self consistent and comprehensive fundamental understanding of the mechanisms that are responsible for the observed phenomena. The intellectual merits of the proposal can broadly be defined as: (1) characterizing the proton transport in polymer ultra-thin films, (2) developing a fundamental model to explain the physiochemical properties of polymer ultra-thin films, and (3) exploiting the observed behavior to produce enhanced capabilities for proton exchange membranes for fuel cells using existing materials and processes. The broader impacts of this activity include: (1) providing guidance on and opportunities for overcoming some of the roadblocks in microlithography to benefit the microelectronics industry, (2) providing a way to enhance polymer membrane performance for fuel cells, (3) educating undergraduate and graduate students in a manner that synergistically blends modeling and experiment, and (4) enhancing underrepresented and minority student education and improving secondary school science education.