CAREER: Mechano-Adaptive Polymers with Reversible Strain Stiffening and Softening via Active Control of Metal-Ligand Interactions

职业：通过主动控制金属-配体相互作用实现可逆应变硬化和软化的机械适应性聚合物

• 批准号: 2238935
• 负责人: Ying Yang
• 金额: $ 60.13万
• 依托单位: Board of Regents, NSHE, obo University of Nevada, Reno
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-08-01 至 2028-07-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2238935&HistoricalAwards=false
• 关键词: CAREER; Mechano; Adaptive; Polymers; Reversible

NON-TECHNICAL SUMMARYThe mechanical and elastic properties of synthetic polymers are one reason why they have become ubiquitous in modern life. However, comparatively, biomaterials exhibit unmatchable dynamics and complex mechanical behaviors. This has motivated materials scientists and engineers for years to push the limit of synthetic polymers to approach the functionalities of biomaterials. This project is inspired by the mechanics of biological cells. Actin, which plays an important role in supporting cell mechanical integrity, shows stiffening followed by softening under mechanical stress. The stiffening protects the cell from initial impact while the softening prevents catastrophic fracture. These mechano-responses are fully reversible. Imparting this mechanical reversibility of “stiffening-softening” to synthetic polymers will enable unprecedented mechano-adaptation and allow the materials to actively adjust their shape and stiffness in response to the mechanical environment, becoming resistant to both low and high impacts. These properties have not been realized in synthetic polymers. As such, this project aims to develop polymeric materials with tailored structures and molecular interactions to achieve similar mechanics. The results will advance the limited understanding of controlling the nonlinear mechanics of complex molecular networks. It will set the stage toward materials that emulate mechanobiology to have force-regulated sensing, signaling, and morphing functionalities. The project will be integrated with strategic education and outreach plans centered on virtual reality (VR) demonstrations to engage a diverse group of students and promote polymer science education in Northern Nevada. TECHNICAL SUMMARYBiomaterials exhibit unmatchable dynamics and complex mechanical behaviors compared to synthetic polymers. Supramolecular polymers with tunable noncovalent bonds provide an opportunity to bridge this gap. Intensive research has been conducted to elucidate the interdependencies of material properties, polymer architectures, and the characteristics of the associative groups. However, active control of the dynamics of the associative bonds by mechanical force is still understudied. Thus, this project will elucidate the use of this dynamic parameter by focusing on the change of sticker kinetics during mechanical perturbation in a nonequilibrium state, in order to access the complex nonlinear viscoelasticity for responsive networks. The nonlinear mechanics of interest is the “stiffening-softening paradox” of living cells. They stiffen under low strains to resist the initial impact, soften at high strains to prevent catastrophic fracture, and recover their original forms upon load removal, representing dynamic adjustments of their mechanical property according to the surrounding environment. The project plans to develop a solvent-free polymer that contains tailored noncovalent bonds, whose associative interactions can be actively adjusted with force in a multi-component system assembled from linear-bottlebrush-linear triblock copolymers. Each component would provide complementary properties to realize complex nonlinear mechanics. This study will address the fundamental question as to how different structural components independently dominate the macroscopic viscoelasticity in certain force ranges, and when their coupled effects become dominant. A combination of synthetic approaches and mechanical & spectroscopic characterization methods will be used to probe their interactions. Understanding the interplay between multi-component systems will serve as a springboard to emulate living materials, which rely on multi-component hierarchical structures to optimize living functions. .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.

非技术总结合成聚合物的机械和弹性性能是它们在现代生活中无处不在的原因之一。然而，相比之下，生物材料表现出无与伦比的动力学和复杂的力学行为。这促使材料科学家和工程师多年来推动合成聚合物的极限，以接近生物材料的功能。这个项目的灵感来自于生物细胞的力学。肌动蛋白在支持细胞机械完整性中起重要作用，在机械应力下表现出硬化和软化。硬化保护电池免受初始冲击，而软化防止灾难性断裂。这些机械反应是完全可逆的。赋予合成聚合物这种“硬化-软化”的机械可逆性将实现前所未有的机械适应性，并允许材料响应机械环境主动调整其形状和刚度，从而能够抵抗低冲击和高冲击。这些特性在合成聚合物中还没有实现。因此，该项目旨在开发具有定制结构和分子相互作用的聚合物材料，以实现类似的力学。这一结果将促进对复杂分子网络非线性力学控制的有限理解。它将为模仿机械生物学的材料奠定基础，使其具有力调节的传感，信号和变形功能。该项目将与以虚拟现实（VR）演示为中心的战略教育和推广计划相结合，以吸引多元化的学生群体，并促进北方内华达州的聚合物科学教育。技术概述与合成聚合物相比，生物材料表现出无与伦比的动力学和复杂的机械行为。具有可调非共价键的超分子聚合物提供了弥合这一差距的机会。已经进行了深入的研究，以阐明材料性能，聚合物结构和缔合基团的特征的相互依赖性。然而，通过机械力对缔合键的动力学进行主动控制仍然研究不足。因此，这个项目将阐明使用这个动态参数，专注于在非平衡状态下的机械扰动过程中的贴纸动力学的变化，以访问响应网络的复杂的非线性粘弹性。感兴趣的非线性力学是活细胞的“硬化-软化悖论”。它们在低应变下软化以抵抗初始冲击，在高应变下软化以防止灾难性断裂，并在载荷移除后恢复其原始形式，代表其机械性能根据周围环境的动态调整。该项目计划开发一种无溶剂的聚合物，其中含有定制的非共价键，其缔合相互作用可以在由线性-瓶刷-线性三嵌段共聚物组装的多组分系统中通过力进行主动调节。每个组件将提供互补的属性，以实现复杂的非线性力学。这项研究将解决的基本问题，不同的结构组件如何独立地主导在一定的力范围内的宏观粘弹性，以及当他们的耦合效应成为主导。将使用合成方法和机械光谱表征方法的组合来探测它们的相互作用。了解多组分系统之间的相互作用将成为模拟生命材料的跳板，生命材料依赖于多组分层次结构来优化生命功能。 该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。