CAREER: Vitrimer gels as a platform for homogenous and meso/nanostructured networks

该奖项的全部或部分资金来自《2021年美国救援计划法案》(公法117-2)。非技术概述：玻璃剂是一种相对较新的聚合物类型，不溶于水，但在高温下仍能流动。这些自相矛盾的特性--在任何其他类型的聚合物中都找不到--使玻璃剂具有机械强度高、耐化学腐蚀性和可回收利用的特点。虽然玻璃化研究主要集中在干散装材料上，但玻璃化凝胶(材料用液体溶剂膨胀)也被预测具有独特的性质。与传统的聚合物凝胶不同，玻璃化凝胶预计会有最小的结构缺陷。增加玻璃剂和溶剂之间的相互作用强度有望诱导凝胶组装成复杂的纳米结构。这种行为催生了适应性材料的开发，这些材料可以根据命令切换性能，这是制造更安全的电池和更有效的分离膜和催化剂支架所必需的。为此，这项工作将确定玻璃化凝胶的分子设计原则。通过调节玻璃剂和溶剂之间的相互作用，可以实现具有均匀或复杂纳米结构的凝胶。这项研究的成功将揭开新一代具有自适应纳米结构的温度响应性聚合物材料的序幕。为了加强研究目标，教育计划将鼓励未被充分代表的少数族裔(URM)高中生攻读STEM博士学位。为了实现这一目标，来自塔拉哈西当地一所高中的学生将通过课堂上的科学实验和PI实验室的暑期研究实习，向学生介绍STEM榜样和研究机会。技术摘要：玻璃体是一种动态的聚合物网络，具有缔合交联链(XL)，它保持网络连接但进行交换反应。玻璃体表现出独特的结构和热力学特性，这将为获得具有适应性的介观和纳米结构的温度响应材料开辟新的途径。具体地说，这项拟议的工作将研究玻璃凝胶，在这种凝胶中，网络因溶剂而膨胀。理论和模拟预测，缔合XL导致玻璃体凝胶具有最小的网络缺陷，并诱导相分离成富玻璃体和富溶剂的区域。为了解决理论和实验之间的知识差距，PI和他的学生将阐明缔合XL如何影响玻璃体凝胶网络的拓扑结构和自组装。其具体目标是(I)开发合成路线来制备模型玻璃体凝胶，(Ii)研究均相单相凝胶的网络结构，以及(Iii)研究介观和纳米结构凝胶的相行为和动力学。拟议的方法将建立更具适应性的凝胶作为适应性材料，其形态随着刺激的响应而启动，从而满足能量储存、分离和催化方面的迫切技术需求。主要教育目标是创建一个推广计划，鼓励未被充分代表的少数族裔(URM)高中生攻读STEM博士学位。该计划将与当地一所高中合作，通过以下方式向URM高中生介绍STEM榜样和研究机会：(I)指导他们完成与聚合物相关的课堂实验；(Ii)将正在崛起的URM高中生安排在暑期研究实习中从事更透明的凝胶项目-从而整合研究和教育推动力。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。

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2).NON-TECHNICAL SUMMARY:A vitrimer is a relatively new type of polymer that is insoluble yet still flows at high temperatures. These paradoxical traits – not found in any other type of polymer – enable vitrimers to be mechanically robust, chemically resistant, and also recyclable. While vitrimer research has mostly focused on dry bulk materials, vitrimer gels (where the material is swollen with a liquid solvent) are also predicted to have unique properties. Unlike conventional polymer gels, vitrimer gels are expected to have minimal structural defects. Increasing the interaction strength between the vitrimer and solvent is anticipated to induce the gel to assemble into a complex nanostructure. Such behavior invites the development of adaptable materials that switch properties on command, which are needed for creating safer batteries, and more efficient separations membranes and catalyst scaffolds. To that end, this work will determine the molecular design principles of vitrimer gels. Through tuning the interactions between vitrimer and solvent, gels with either uniform or complex nanostructures will be realized. Success in this research will unlock a new generation of temperature responsive polymer materials with adaptable nanostructures. Augmenting the research objectives, the education plan will encourage underrepresented minority (URM) high school students to pursue STEM PhD degrees. To achieve this goal, students from a local Tallahassee high school will be introduced to STEM role models and research opportunities through in-class science experiments and summer research internships in the PI’s laboratory.TECHNICAL SUMMARY:A vitrimer is a dynamic polymer network that has associative cross-links (XLs), which maintain network connectivity but undergo exchange reactions. Vitrimers express unique structural and thermodynamic traits that will open new pathways towards temperature responsive materials with adaptable meso- and nanostructures. Specifically, the proposed work will investigate vitrimer gels, where the network is swollen by solvent. Theory and simulations predict that associative XLs cause vitrimer gels to have minimal network defects, and induce phase separation into vitrimer-rich and solvent-rich domains. To address the knowledge gap between theory and experiment, the PI and his students will elucidate how associative XLs affect vitrimer gel network topology and self-assembly. The specific aims are to (I) develop synthetic routes to prepare model vitrimer gels, (II) investigate the network structure of homogeneous single-phase gels, and (III) examine the phase behavior and dynamics of meso- and nanostructured gels. The proposed approach will establish vitrimer gels as adaptable materials whose morphologies actuate in response to a stimulus, thereby satisfying urgent technological needs in energy storage, separations, and catalysis.The main educational objective is to create an outreach program to encourage underrepresented minority (URM) high school students to pursue a PhD in STEM. Collaborating with a local high school, the program will introduce URM high school students to STEM role models and research opportunities by (I) guiding them through in-class polymer-related experiments and (II) placing rising URM high school seniors in summer research internships to work on vitrimer gel projects – thereby integrating the research and educational thrusts..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.