CAREER: Mechanochemical Activation in Ordered Polymer Networks

非技术性总结：在分子间施加力是驱动化学反应的一种强有力的方式。这种力敏感分子可以用来制造报告其自身完整性的材料，在损坏后自我修复，或者允许使用力来控制反应发生的时间和地点。聚合物是这些类型的材料的有用平台，因为它们可以充当“分子手柄”，用于将施加到块体材料的力传递到分子尺度。然而，设计有效且均匀地将力传递到分子尺度的聚合物仍然是一个重大挑战。在这个项目中，PI和她的学生将通过合成和表征具有纳米级明确连接性和内部结构的力响应聚合物来应对这一挑战。这项工作将使人们对力在聚合物材料中的分布有新的理解，并为实际应用中的力响应聚合物材料的设计提供信息。该项目还将通过开发用于本科聚合物科学课程的主动学习课堂活动、创建以不同女性角色模型为特色的视频演示以及建立女性化学小组为PI部门的女学生提供指导和专业发展机会，为聚合物科学的教育和扩大参与做出贡献。设计有效地将宏观力转化为分子尺度的聚合物平台对于机械化学的实际应用至关重要。在这项工作中，PI和她的学生将研究聚合物材料的网络结构和纳米结构如何决定应变下聚合物网络中力的分子尺度分布。将开发三个模型系统来研究这一现象。首先，为了检验更均匀的网络将驱动更有效的机械化学活化的假设，含螺吡喃的聚合物将被交联成定义明确的网络，并研究作为网络连接性，网络链分散性和缺陷含量的函数的力诱导的活化率。第二，研究物理交联材料中纳米结构和竞争性结构弛豫的作用，将在自组装成有序纳米级形态的三嵌段共聚物中研究机械化学活化。最后，将开发新的策略，以使聚合物链中的机械载体精确定位，然后将用于测试纳米级界面附近的链拉伸如何用于促进或抑制力驱动的化学过程。这些研究目标将为聚合物网络中分子尺度的强制分布带来基本的见解，并为功能性机械化学活性材料的设计规则提供信息。这些研究目标将与旨在扩大参与和改善聚合物科学教育的几项教育和推广活动相结合。PI将为聚合物科学开发和分发过程导向的指导探究学习（POGIL）活动。她还将创建视频演示的重要主题在聚合物科学具有女性主持人作为榜样感兴趣的学生。最后，她将为她所在系的学生建立一个女性化学小组，作为促进新的指导机会和扩大女学生参与科学事业的机制。该奖项反映了NSF的法定使命，并通过使用基金会的智力价值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:Applying force across molecules is a powerful way to drive chemical reactions. Such force-sensitive molecules can be used to make materials that report on their own integrity, that self-heal after damage, or that allow force to be used to control when and where a reaction takes place. Polymers are a useful platform for these types of materials because they can act as "molecular handles" for transmitting forces applied to a bulk material down to the molecular scale. However, designing polymers that efficiently and uniformly transmit forces to the molecular scale remains a significant challenge. In this project, the PI and her students will address this challenge by synthesizing and characterizing force-responsive polymers with well-defined connectivity and internal structure at the nanometer scale. This work will enable new understanding of how forces are distributed in polymeric materials and inform design of force-responsive polymeric materials for practical applications. This project will also contribute to education and broadened participation in polymer science through development of active learning classroom activities for use in undergraduate polymer science courses, creation of video demonstrations featuring diverse female role models, and establishment of a women-in-chemistry group to provide mentoring and professional development opportunities for female students in the PI's department.TECHNICAL SUMMARY: Designing polymeric platforms that efficiently transduce macroscopic forces to the molecular scale is critical for practical applications of mechanochemistry. In this work, the PI and her students will investigate how the network structure and nanostructure of polymeric materials determine the molecular-scale distribution of forces in polymer networks under strain. Three model systems will be developed to investigate this phenomenon. First, to test the hypothesis that more uniform networks will drive more efficient mechanochemical activation, spiropyran-containing polymers will be crosslinked into well-defined networks, and force-induced activation rates studied as a function of network connectivity, network strand dispersity, and defect content. Second, to investigate the roles of nanostructure and competing structural relaxations in physically crosslinked materials, mechanochemical activation will be studied in triblock copolymers that self-assemble into well-ordered nanoscale morphologies. Finally, new strategies will be developed to enable precise placement of mechanophores within polymer chains, and will then be used to test how chain stretching near nanoscale interfaces can be used to promote or suppress force-driven chemical processes. Together, these research aims will bring fundamental insight to molecular-scale forced distributions in polymer networks and inform design rules for functional mechanochemically-active materials.These research aims will be integrated with several education and outreach activities aimed at broadening participation and improving education in polymer science. The PI will develop and distribute Process-Oriented Guided Inquiry Learning (POGIL) activities for polymer science. She will also create video demonstrations of important topics in polymer science featuring female presenters as role models for interested students. Finally, she will establish a women-in-chemistry group for students in her department as a mechanism for promoting new mentoring opportunities and broaden female students' participation in the scientific enterprise.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.