Quantifying the Polymer Physics of Mechanical Deformation in Ultra-thin Polymer Glasses

量化超薄聚合物玻璃机械变形的聚合物物理

• 批准号: 1608614
• 负责人: Alfred Crosby
• 金额: $ 40.5万
• 依托单位: University of Massachusetts Amherst
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-05-01 至 2019-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1608614&HistoricalAwards=false
• 关键词: Quantifying; Polymer; Physics; Mechanical; Deformation

NON-TECHNICAL SUMMARY Numerous technologies rely upon the properties and performance of thin polymer films. For example, membranes used in clean water applications are comprised of thin polymer layers through which water is pushed to separate and remove unwanted contaminants. Although currently useful, this technology remains energetically unfavorable due to engineering limits with regard to the mechanical strength of polymer thin films. Beyond membranes, the efficiency and lifetime of many other applications are also limited by the mechanical properties of polymer thin films; however, direct knowledge of these properties in thin films is extremely limited. Changes in polymer materials when they are processed into films comprised of only a few molecules in thickness are well known, but how these changes impact mechanical strength remains unclear. The proposed project will overcome current challenges with directly measuring mechanical properties in ultra-thin polymers, leading to new fundamental data and knowledge that can help guide the design and synthesis of new materials for better membranes, alternative power sources, as well as many other technologies. The proposed research will provide a strong foundation for the education and training of multiple graduate students and undergraduate researchers. To extend the impact of this project to the K-12 education level, new materials science and engineering curriculum materials will be developed to be integrated into a workshop, called BioInspire!. This program is designed to teach lessons of materials science and engineering and biology in the context of bioinspired innovation, where science, engineering, and art can be used to engage a broad, diverse group of students.TECHNICAL SUMMARYThis project will develop fundamental knowledge of the polymer physics associated with the mechanical properties in ultra-thin films of polymer glasses. Although changes in the mobility of glassy polymer chains in a surface-dominated regime has been studied extensively, the mechanical properties in ultrathin polymer films have only been studied to a limited extent. Here, a new measurement device, called the Ultrathin Film Tensile tester (UFT), will be used to measure the complete stress-strain relationship for polymer thin films under uniaxial extension conditions. The proposed measurements will provide a complete understanding of mechanical responses in ultra-thin polymer films by quantifying elastic and dissipative processes through monotonic and cyclic loading histories across a wide strain and temperature range, as well as controlled fracture experiments in the dimensionally-constrained regime. Three materials systems, including polystyrene (PS), polycarbonate (PC), and blends of polystyrene and poly(2,6-dimethyl-1,4-phenylene oxide) (PS/PPO), will be studied, allowing molecular structure and mechanical responses to be tuned systematically. The findings are expected to provide new insight with regards to how polymer mobility changes near a surface can alter the constitutive response of a polymer, how changes in entanglement density due to dimensional geometric constraints alters fracture mechanisms, and how geometric constraints on polymer molecules may alter the onset of dissipative or plastic deformations. The findings from this project will have a significant impact on fundamental polymer physics, as well as on the development of new characterization methods that can aid the development of advanced materials for thin film applications.

许多技术都依赖于聚合物薄膜的特性和性能。例如，用于净水应用的膜是由薄聚合物层组成的，水通过它被推动分离并去除不需要的污染物。虽然目前很有用，但由于聚合物薄膜机械强度的工程限制，这项技术在能量上仍然不利。除了薄膜，许多其他应用的效率和寿命也受到聚合物薄膜机械性能的限制；然而，对薄膜中这些特性的直接了解是非常有限的。当聚合物材料被加工成只有几个分子厚度的薄膜时，它们的变化是众所周知的，但是这些变化是如何影响机械强度的还不清楚。该项目将克服目前直接测量超薄聚合物机械性能的挑战，带来新的基础数据和知识，有助于指导新材料的设计和合成，以获得更好的膜，替代能源，以及许多其他技术。建议的研究将为多个研究生和本科生研究人员的教育和培训提供坚实的基础。为了将该项目的影响扩展到K-12教育水平，将开发新材料科学和工程课程材料，并将其整合到一个名为“BioInspire!”的研讨会中。该课程旨在在生物启发创新的背景下教授材料科学、工程和生物学课程，科学、工程和艺术可以用来吸引广泛、多样化的学生群体。本项目将发展与超薄聚合物玻璃薄膜机械性能相关的聚合物物理基础知识。虽然玻璃聚合物链在表面占主导地位的迁移率的变化已经被广泛研究，但超薄聚合物薄膜的机械性能只在有限的程度上进行了研究。在这里，一种新的测量设备，称为超薄薄膜拉伸测试仪（UFT），将用于测量聚合物薄膜在单轴拉伸条件下的完整应力-应变关系。所提出的测量将通过在宽应变和温度范围内的单调和循环加载历史，以及在尺寸约束下的受控断裂实验，量化弹性和耗散过程，从而全面了解超薄聚合物薄膜的机械响应。三种材料体系，包括聚苯乙烯（PS），聚碳酸酯（PC），以及聚苯乙烯和聚（2,6-二甲基-1,4-苯乙烯氧化物）（PS/PPO）的共混物，将被研究，允许分子结构和机械响应被系统地调整。这些发现有望为以下方面提供新的见解：表面附近聚合物迁移率的变化如何改变聚合物的本构响应，由于尺寸几何约束而导致的纠缠密度的变化如何改变断裂机制，以及聚合物分子的几何约束如何改变耗散或塑性变形的发生。该项目的研究结果将对基础聚合物物理学产生重大影响，并对新的表征方法的发展产生重大影响，这些方法可以帮助开发用于薄膜应用的先进材料。