Silyl Ether Metathesis for Universal Vitrimer Design

非技术总结：该项目的主要目标是开发一种由聚合物制成的动态材料的新方法，该方法可以将优异的机械性能和化学稳定性与良好的再加工性和可回收性相结合。聚合物材料在应对包括替代能源、医疗/健康和国家安全/竞争力在内的许多技术挑战方面发挥着至关重要的作用。广义上，聚合物材料分为两大类：热固性材料和热塑性塑料。热固性树脂的分子是永久连接的(“交联”)，因此具有优异的机械性能、尺寸稳定性以及耐化学品和溶剂的性能。然而，热固性树脂的一个关键限制是它们不能重塑、再加工或回收，因为它们的分子是永久缝合在一起的。相比之下，热塑性聚合物可以重塑和再加工，但它们通常机械强度较低，高温下结构稳定性较差，耐化学/溶剂性能较差。这项研究提出了一种新的化学策略，旨在结合热塑性塑料和热固性塑料的最佳属性。具体地说，将探索一种普遍的战略，通过一种新的硅-氧交换反应，将可塑性、可再加工性和可回收性引入各种聚合物网络和复合材料。拟议战略的成功示范可能会对新材料开发、聚合物回收和可持续性以及包括添加剂制造在内的现代加工技术产生重大影响。该项目还将提供广泛的机会来培训研究生和本科生，包括在科学领域代表性不足的群体。该项目还将使PI能够与UCI数学、工程、科学成就(MESA)计划合作，开展K-12材料科学/化学扩展工作，其中一个模块侧重于动态/自修复聚合物。技术摘要：本研究的主要目标是研究硅醚歧化作用作为一种新的、健壮的、通用的动态共价化学，用于设计动态聚合物材料。永久交联型聚合物(即热固性聚合物)具有优异的力学性能、抗蠕变性能和尺寸稳定性，以及耐化学/溶剂性能。然而，热固性树脂的一个关键限制是它们不能通过加热或溶剂进行重塑、再加工或回收。相比之下，热塑性聚合物可以重塑和再加工，但它们通常机械强度较低，高温下结构稳定性较差，耐化学/溶剂性能较差。该项目描述了一种新的化学策略，旨在结合热塑性塑料(可再加工、可回收)和热固性(机械强度、蠕变和耐溶剂性)的优良属性。具体地说，提出了一种通用的策略，通过一种新的硅醚歧化反应将塑性、可再加工性和可回收性引入到各种聚合物网络和复合材料中。首先，将对普通商品聚合物制成的玻璃体的硅醚歧化反应的一般适用性进行研究(目标1)。目的2详细介绍了由多个聚合物通过动态反应共混合成玻璃化聚合物的方案。这提供了一种定制和改进玻璃剂性能的简单方法。将仔细研究生成的玻璃体的动态机械性能，并将其与结构相关联。最后，将所提出的策略扩展到通过无机表面和有机聚合物基质之间的硅醚歧化反应来设计无机/有机复合玻璃聚合物(目标3)。同样，将对复合玻璃体进行结构-性能研究。建议战略的成功演示可能会对新材料开发、聚合物回收和可持续发展以及包括添加剂制造在内的现代技术产生重大影响。该奖项反映了NSF的法定使命，并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，被认为值得支持。

NON-TECHNICAL SUMMARY:The main objective of this project is to develop a new method for producing dynamic materials made out of polymers that can combine excellent mechanical properties and chemical stability with good reprocessability and recyclability. Polymeric materials play an essential role in addressing many technological challenges including alternative energy, medical/health, and national security/competitiveness. Broadly defined, polymeric materials are classified into two large categories: thermosets and thermoplastics. Thermosets have their molecules permanently connected ("cross-linked") and as a result have excellent mechanical properties, dimensional stability, and resistance to chemicals and solvents. However, a critical limitation of thermosets is that they cannot be reshaped, reprocessed, or recycled since their molecules are permanently stitched together. In contrast, thermoplastic polymers can be reshaped and reprocessed, but they normally have lower mechanical strength, lower structural stability at elevated temperature, and poorer chemical/solvent resistances. This research presents a new chemical strategy that aims to combine the best attributes of both thermoplastics and thermosets. Specifically, a universal strategy will be explored to introduce plasticity, reprocessability and recyclability to various polymer networks and composites through a new silicon-oxygen exchange reaction. Successful demonstration of the proposed strategy could offer significant impact on new materials development, polymer recycling and sustainability, and modern processing technologies including additive manufacturing. This project will also provide extensive opportunities to train graduate and undergraduate students, including underrepresented groups in science. This project will also enable the PI to work with the UCI Mathematics, Engineering, Science Achievement (MESA) Program on a K-12 materials science/chemistry outreach effort with a module focusing on dynamic/self-healing polymers.TECHNICAL SUMMARY:The main objective of this research is to investigate silyl ether metathesis as a new, robust, and universal dynamic covalent chemistry for the design of dynamic polymeric materials. Permanently cross-linked polymers (i.e., thermosets) have excellent mechanical properties, creep resistance and dimensional stability, and chemical/solvent resistance. However, a critical limitation of thermosets is that they cannot be reshaped, reprocessed, or recycled by heat or with solvent. In contrast, thermoplastic polymers can be reshaped and reprocessed, but they normally have lower mechanical strength, lower structural stability at elevated temperature, and poorer chemical/solvent resistances. This project describes a new chemical strategy that aims to combine the excellent attributes of both thermoplastics (reprocessability, recyclability) and thermosets (mechanical strength, creep and solvent resistances). Specifically, a universal strategy is proposed to introduce plasticity, reprocessability and recyclability to various polymer networks and composites through a new silyl ether metathesis reaction. First, the general applicability of silyl ether metathesis will be investigated for vitrimers made of common commodity polymers (Aim 1). Aim 2 details plans for the synthesis of vitrimers from multiple polymers through dynamic reactive blending. This provides a simple way to tailor and improve vitrimer properties. The dynamic mechanical properties of the resulting vitrimers will be carefully investigated and correlated with the structures. Finally, the proposed strategy is extended to the design of inorganic/organic composite vitrimers through silyl ether metathesis between inorganic surfaces and organic polymer matrices (Aim 3). Similarly, structure-property studies will be conducted for the composite vitrimers. Successful demonstration of the proposed strategy could offer significant impact on new materials development, polymer recycling and sustainability, and modern technologies including additive manufacturing.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.