CAREER: Formation of Stable Polymer Glasses

技术摘要：玻璃的性质很大程度上取决于玻璃形成的途径。通过物理气相沉积可以形成低能量、超稳定的有机分子玻璃。这种生产超稳定玻璃的方法不适用于聚合物。因此，低能量、超稳定聚合物玻璃的形成还没有实现。该职业奖的第一个目标是探索基质辅助脉冲激光蒸发(Maple)作为一种生产低能量、超稳定聚合物薄膜的方法。待探索的工艺参数包括生长速度(瞬时和平均)、衬底温度和沉积分子的动能。将对所有薄膜的稳定性、形貌和机械性能进行表征。这一职业的第二个目标是探索稳定玻璃形成的机制。在这里，提出了新的实验来探索稳定的玻璃形成和表面迁移率之间的关系。首先，将比较不同表面流动性增强的聚合物玻璃的稳定性。其次，比较了不同比表面积/体积比的聚合物膜的稳定性。第三，将开发一种独特的荧光多层方法，允许直接测量自由表面稳定性和能量-景观表面。这项提议将解决的基本问题包括：表面迁移率更高的薄膜是否会形成更稳定的玻璃？表面分子能够探索较低的能态吗？非技术总结：这项工作解决了与低能、稳定的玻璃形成有关的基本问题，最终，这项工作有朝一日可能为开发具有无与伦比的热稳定性和动力学稳定性的聚合物玻璃提供指导。这项建议将探索一种可能的应用，稳定的聚合物玻璃作为超阻隔膜。这些材料的其他潜在应用包括1)基于有机发光二极管技术的显示器，具有对环境因素(例如，湿度、温度波动)的增强的稳定性，以及更低的功耗，2)具有更高形态稳定性的有机电子产品，以及3)表现出更强的抗污染物能力的涂层和保护皮肤。新发现的低能量、稳定的玻璃将被纳入一门关于玻璃转变的新本科生/研究生选修课。这项拟议的研究将由一个由高中、本科生和研究生组成的不同团队完成。这一职业奖概述了一个独特的四级教育和推广计划，旨在增加代表不足的少数族裔和来自经济困难背景的学生对科学感兴趣、获得STEM学位和参与学术研究的人数。该外展计划旨在促进科学职业道路上各个层面的科学参与。

TECHNICAL SUMMARY: The properties of glasses strongly depend on the path to glass formation. Low energy, ultra-stable organic molecular glasses can be formed by physical vapor deposition. This route to producing ultra-stable glasses is not amenable to polymers. As such, the formation of low energy, ultra-stable polymer glasses have not been realized. The first objective of this CAREER award is to explore Matrix Assisted Pulsed Laser Evaporation (MAPLE) as a route to produce low-energy, ultra-stable polymer films. Processing parameters to be explored include growth rate (both instantaneous and average), substrate temperature, and kinetic energy of the depositing molecule. The stability, morphology, and mechanical properties will be characterized for all films. The second objective of this CAREER is to explore the mechanism of stable glass formation. Here, new experiments are proposed to explore the relationship between stable glass formation and surface mobility. First, the stability of polymer glasses that exhibit different enhanced surface mobility will be compared. Second, the stability of polymer films formed with different surface area/volume ratios will be compared. Third, a unique fluorescence multilayer approach that will allow for the direct measurement of free surface stability and energy-landscape surface will be developed. Fundamental questions this proposal will address include: Do films with greater surface mobility form more stable glasses? Are surface molecules able to explore lower energy states? NON-TECHNICAL SUMMARY: The work addresses fundamental questions concerning low-energy, stable glass formation, and, ultimately, the work may someday provide guidelines for the development of polymer glasses with unmatched thermal and kinetic stability. This proposal will explore one possible application of stable polymer glasses as ultra-barrier membranes. Other potential applications of these materials include 1) displays based on organic light-emitting diode technology, possessing enhanced stability to environmental factors (e.g., humidity, temperature fluctuations), and lower power consumption, 2) organic electronics with greater morphological stability, and 3) coatings and protective skin layers exhibiting greater resistance to contaminants. The new discovery of low energy, stable glasses will be incorporated into a new undergraduate/graduate elective course on the glass transition. The proposed research will be accomplished by a diverse team of high school, undergraduate and graduate students. This CAREER award outlines a unique 4-tier educational and outreach program to increase the number of underrepresented minorities and students from economically disadvantaged backgrounds interested in science, obtaining STEM degrees, and participating in academic research. The outreach program is designed to promote scientific involvement at all levels of a scientific career path.