CAREER: Mechanochemical Activation in Ordered Polymer Networks

非技术综述：跨分子施加力是推动化学反应的一种有效方法。这种对力敏感的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。聚合物是这些类型材料的有用平台，因为它们可以充当“分子手柄”，将施加在大宗材料上的力传递到分子级别。然而，设计高效、均匀地将力传递到分子尺度的聚合物仍然是一个巨大的挑战。在这个项目中，PI和她的学生将通过在纳米级合成和表征具有明确连接性和内部结构的力响应聚合物来应对这一挑战。这项工作将使人们能够对力在聚合物材料中的分布有新的理解，并为实际应用中力响应型聚合物材料的设计提供参考。这个项目还将通过发展用于本科生聚合物科学课程的主动学习课堂活动，创建以不同女性榜样为特色的视频演示，以及建立一个妇女化学小组，为PI系的女学生提供指导和职业发展机会，促进教育和扩大对聚合物科学的参与。技术摘要：设计能够有效地将宏观作用力转换到分子尺度的聚合物平台对于机械力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在应变下聚合物网络中的力的分子尺度分布。将开发三个模型系统来研究这一现象。首先，为了验证更均匀的网络将驱动更有效的机械力化学活化的假设，含有螺吡喃的聚合物将被交联成定义良好的网络，并研究作为网络连通性、网络链分散性和缺陷含量的函数的力诱导激活率。其次，为了研究纳米结构和竞争结构弛豫在物理交联材料中的作用，将研究自组装成有序纳米级形态的三嵌段共聚物中的机械力化学活化。最后，将开发新的策略，使机械团能够精确地放置在聚合物链中，然后将用于测试如何使用纳米级界面附近的链拉伸来促进或抑制力驱动的化学过程。总之，这些研究目标将带来对聚合物网络中分子尺度强迫分布的基本见解，并为功能性机械力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个教育和推广活动相结合。PI将为聚合物科学开发和分发面向过程的指导性研究性学习(POGIL)活动。她还将制作聚合物科学重要主题的视频演示，将女性演讲者作为感兴趣的学生的榜样。最后，她将为她所在系的学生建立一个化学女性小组，作为促进新的指导机会和扩大女性学生参与科学事业的机制。这一奖项反映了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: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.