Tailoring Size and Shape of beta-Sheet Nanocrystals for Crosslinking and Reinforcement of Elastomers

用于弹性体交联和增强的β-片纳米晶体的尺寸和形状定制

• 批准号: 1610109
• 负责人: Li Jia
• 金额: $ 45万
• 依托单位: University of Akron
• 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: 2016-06-01 至 2020-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1610109&HistoricalAwards=false
• 关键词: Tailoring; Size; Shape; beta; Sheet

NON-TECHNICAL SUMMARY. Elastomers are rubbery materials that are produced on the scale of 200 million tons annually worldwide. Their applications range from daily goods (for example tires) to defense (for example sonar domes of navy ships) and to biomedicine (for example coatings of artery stents). This NSF-supported research/educational team led by a chemist (Jia) and a physicist/chemical engineer (Foster) combines inspirations from biological systems and lessons from chemical and physical principles to develop the next generation of elastomers. A central focus is to reduce the size of hard particles that strengthen the elastomers to the nanometer scale. The research team will advance our fundamental understanding of how these reinforcing elements produce elastomers that are strong, stiff, and extensible and that have programmed capability to dissipate energy. This scientific knowledge can be used for a number of applications, e.g. tires that are safe, durable, and fuel-efficient. The elastomers developed can also potentially be directly applied to make medical devices safer. Parallel to the research effort, the program will train undergraduate and graduate students in this interdisciplinary area. The team will carry out outreach activities aimed at attracting domestic talent to careers in science and technology and particularly in polymer-related areas using aspects of elastomers as the primary content materials.TECHNICAL SUMMARY. The ability to manipulate atoms and molecules to form hierarchical structures with precisely controlled size and shape is central to nanoscience. Beta-sheet nanocrystals exist in both natural and synthetic elastomers and function as crosslinks and provide reinforcement. However, their morphologies are drastically different in these two circumstances. In natural elastomers (i.e., silks), they are particulates with all three dimensions smaller than 10 nm. In synthetic elastomers (e.g., polyurethanes), they have been found to be fibrous with the longest dimension, in the hydrogen-bonding direction, ranging from hundreds of nanometers to microns. In silks, the size control is attributed to specific amino acid sequences and an exquisite reeling process. Controlling the size and aspect ratio of beta-sheet nanocrystals is an unresolved challenge for synthetic systems. This research pursues this central quest of nanoscience in an important area of soft materials, elastomers, to realize material properties otherwise unattainable. The scientific approach of the research is multifaceted, involving synthesis, characterization, and mechanical studies across the molecular, supramolecular, and nanometer scales. Based on their recent success in reducing the longest dimension of n-beta-sheet nanocrystals in a series of oligo(beta-alanine)-grafted polyisobutylenes to well below 100 nm, the research team will expand their ability to regulate the size and aspect ratio of the beta-sheet nanocrystals without an elaborate aminoacid sequence and to elucidate the reinforcing characteristics of the two morphologically contrasting beta-sheet nanocrystals. The polymer brush at the interface of the nanocrystal will be another focus as it is critical for the morphological control and likely plays an important role in reinforcement as well. The specific objectives of the planned research are to: (1) synthesize monodisperse oligo(beta-alanine)-grafted polyisobutylenes that form particulate nanocrystals with still smaller aspect ratios as well as those that form fibrous nanocrystals. (2) characterize the structures and morphologies of the beta-sheet nanocrystals including the polymer brush attached to the nanocrystal surface. (3) elucidate the reinforcing characteristics and study the reinforcing mechanisms of the particulate and fibrous nanocrystals.

非技术摘要。 弹性体是橡胶材料，全球每年生产2亿吨。它们的应用范围从日常用品（例如轮胎）到国防（例如海军舰艇的声纳圆顶）和生物医学（例如动脉支架涂层）。这个由化学家（Jia）和物理学家/化学工程师（Foster）领导的NSF支持的研究/教育团队将生物系统的灵感与化学和物理原理的教训相结合，以开发下一代弹性体。中心焦点是将增强弹性体的硬颗粒的尺寸减小到纳米级。研究团队将推进我们对这些增强元件如何生产坚固、坚硬、可延伸并且具有程序化能量消散能力的弹性体的基本理解。这些科学知识可以用于许多应用，例如安全，耐用和省油的轮胎。开发的弹性体也可以直接用于使医疗器械更安全。平行的研究工作，该计划将培养本科生和研究生在这个跨学科领域。该团队将开展外展活动，旨在吸引国内人才从事科学技术职业，特别是使用弹性体作为主要内容材料的聚合物相关领域。技术摘要。 操纵原子和分子以形成具有精确控制的大小和形状的分级结构的能力是纳米科学的核心。β-片层纳米晶体存在于天然和合成弹性体中，起交联作用并提供增强作用。然而，它们的形态在这两种情况下是截然不同的。在天然弹性体（即，丝），它们是所有三个维度都小于10 nm的颗粒。在合成弹性体（例如，聚氨酯），已经发现它们是纤维状的，在氢键方向上具有最长的尺寸，范围从数百纳米到微米。在丝绸中，尺寸控制归因于特定的氨基酸序列和精致的缫丝过程。控制β-折叠纳米晶体的尺寸和纵横比是合成系统的一个未解决的挑战。 本研究在软材料，弹性体的重要领域追求纳米科学的核心追求，以实现材料特性，否则无法实现。 研究的科学方法是多方面的，涉及分子，超分子和纳米尺度的合成，表征和机械研究。基于他们最近成功地将一系列寡聚（β-丙氨酸）接枝聚异丁烯中的n-β-折叠纳米晶体的最长尺寸降低到远低于100 nm，研究小组将扩大他们在没有精心设计的氨基酸序列的情况下调节β-折叠纳米晶体的尺寸和纵横比的能力，并阐明两种形态对比的β-折叠纳米晶体的增强特性。聚合物刷在界面处的粘结将是另一个焦点，因为它是关键的形态控制，并可能发挥重要的作用，以及在增强。 计划研究的具体目标是：（1）合成单分散低聚（β-丙氨酸）-接枝聚异丁烯，形成具有更小纵横比的颗粒纳米晶体以及形成纤维状纳米晶体的那些。 (2)表征了包括附着于纳米表面的聚合物刷的β-片层纳米晶体的结构和形态。 (3)阐明了颗粒状和纤维状纳米晶的增强特性，并研究了其增强机理。