RUI: Dynamic Guanidine-based Polymer Networks

RUI：动态胍基聚合物网络

• 批准号: 2105149
• 负责人: Michael Larsen
• 金额: $ 33万
• 依托单位: Western Washington University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-06-15 至 2025-05-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2105149&HistoricalAwards=false
• 关键词: RUI; Dynamic; Guanidine; based; Polymer

PART 1: NON-TECHNICAL SUMMARYPolymeric materials can generally be divided into two categories: (a) thermoplastics, materials such as plastic bottles, grocery bags, and nylon, that soften with heat and can be remolded and recycled; and (b) thermosets, those such as tires, epoxy adhesives, and resins, that have a permanent shape and are very difficult to reprocess. Thermosets thus have limited potential for reuse, ultimately having a negative impact on the environment through resource consumption and accumulation of large amounts of waste material. At the molecular level, the difference between these two classes of materials arises from the fact that thermoplastics consist of discrete polymer chains that can move and flow when heated, whereas thermosets are built from a crosslinked molecular network that is permanently bonded together. To bridge the gap between these materials, recent efforts have focused on making their fixed networks reversible -- that is, enabling them to de-crosslink under certain conditions followed by reformation of the network, allowing thermosets to be remolded and reprocessed. These systems represent a new class of materials known as dynamic polymer networks. While dynamic polymer networks have been the focus of considerable research during the last two decades, many fundamental questions about them remain, detracting from their practical utility and restricting their applications beyond the research lab. This research will leverage the unique characteristics of a novel chemical reaction aimed at de-crosslinking thermosets in order to gain generalized insight into the fundamental principles of dynamic polymer networks. Successful realization of the PI’s research goals will yield a wide variety of reprocessable thermosets and link specific molecular-level characteristics with macroscopic properties, helping to shape future designs and applications of these advanced materials in areas as varied as sustainable manufacturing, advanced medicine, and next-generation batteries. Students participating in this research will be trained in an interdisciplinary manner involving synthetic chemistry, polymer characterization, and a variety of techniques for property determination.PART 2: TECHNICAL SUMMARYDynamic polymer networks are covalently crosslinked materials that combine the desirable properties of thermosets with the reprocessability of thermoplastics. Their crosslinks undergo reversible exchange reactions that are activated under specific conditions, continuously reorganizing the network. Recently the PI demonstrated a new type of these materials based on previously unknown exchange reactions of guanidines. This proposal seeks to leverage the unique capabilities of dynamic guanidine-based polymer networks to answer fundamental questions in the field of dynamic materials and expand the window of achievable properties of these systems. Specific objectives of this proposal are to: (1) use the versatility of the guanidine functionality to both modify its reactivity and introduce noncovalent bonding partners, establishing the link between fundamental molecular-scale properties and macroscopic rheological behavior; and (2) incorporate guanidine crosslinks into a variety of precisely altered polymer structures to elucidate the role of specific characteristics of the “background” polymer in determining the behavior of dynamic networks. These studies will be accomplished by student researchers using a combination of synthetic techniques, polymer characterization, rheological analysis, and dielectric spectroscopy..This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

第 1 部分：非技术概要聚合物材料通常可分为两类：(a) 热塑性材料，例如塑料瓶、购物袋和尼龙，它们受热软化，可以重塑和回收；(b) 热固性材料；轮胎、环氧树脂粘合剂和树脂等具有永久性形状且很难再加工的热固性材料的再利用潜力有限，最终对环境产生负面影响。在分子水平上，这两类材料之间的差异在于，热塑性塑料由离散的聚合物链组成，加热时可以移动和流动，而热固性塑料则由交联聚合物构成。为了弥合这些材料之间的差距，最近的努力集中在使它们的固定网络可逆——也就是说，使它们能够在某些条件下解交联，然后重新形成网络，成为热固性材料。改造和这些系统代表了一种称为动态聚合物网络的新型材料，尽管动态聚合物网络在过去二十年中一直是大量研究的焦点，但仍然存在许多基本问题，影响了它们的实际用途并限制了它们的应用。该研究实验室将利用旨在解交联热固性材料的新型化学反应的独特特性，以获得对动态聚合物网络基本原理的普遍了解，成功实现 PI 的研究目标将产生广泛的成果。可再加工热固性材料并将特定的分子级特性与宏观特性联系起来，有助于塑造这些先进材料在可持续制造、先进医学和下一代电池等领域的未来设计和应用。涉及合成化学、聚合物表征和各种性能测定技术的跨学科方式。第 2 部分：技术摘要动态聚合物网络是共价交联材料，它将热固性材料的理想性能与热塑性塑料的可再加工性结合在一起。交联发生在特定条件下激活的可逆交换反应，不断重组网络。最近，PI 展示了一种基于以前未知的胍交换反应的新型材料。该提案旨在利用动态胍基聚合物的独特功能。该提案的具体目标是：（1）利用胍官能团的多功能性来改变其反应性。并引入非共价键合伙伴，建立基本分子尺度特性和宏观流变行为之间的联系；(2) 将胍交联结合到各种精确改变的聚合物结构中，以阐明“背景”聚合物的特定特征在确定中的作用；这些研究将由学生研究人员结合合成技术、聚合物表征、流变分析和介电光谱来完成。该奖项反映了 NSF 的法定使命，并被认为是值得的。通过使用基金会的智力优势和更广泛的影响审查标准进行评估来提供支持。