CAREER: Gas-regulated Mechanochemical Activation for Bio-inspired Responses in Polymer Networks

非技术总结：在自然界中，生物系统可以对机械力做出建设性的反应，例如皮肤在割伤后的愈合。受此启发，本项目旨在开发力响应型合成高分子材料，该材料可以在施加力后进行重塑。目标是利用二氧化碳作为外部刺激，从外部调节力触发激活和重塑的程度。要做到这一点，材料将包括两个部分。一种成分被设计为通过膨胀来应对二氧化碳，另一种成分包括被称为机械基团的力敏感基团，它将根据膨胀的程度重塑材料。使用这种方法，该项目描述了系统的研究，检查了聚合物网络中机械团激活及其时间尺度的结构-性质关系。该项目将有助于推进研究，开发出安全性更高、使用寿命更长、对环境影响更小的材料。该项目还将包括教育和推广活动，包括为就读于主要本科机构（PUI）的不同背景的本科生提供指导研究机会，基于该项目为聚合物技术选修课开发实践模块，以及实施职业模块，使学生接触该领域的职业道路。此外，该项目支持接待两名有兴趣在PUI工作的访问研究生，他们将在夏季开始建立开发本科生驱动的研究项目所需的技能。技术概述：生物系统对机械力作出建设性反应的能力激发了机械响应聚合物网络的设计，这种网络同样会引起建设性反应。然而，开发具有力触发重塑能力的合成材料的策略仍然有限。这项工作将采取逐步的方法来调节机械化学激活使用外部刺激双网络（DN）水凝胶。使用DN结构，外部控制将由二氧化碳（CO2）响应的初级网络提供，该网络通过膨胀调节次级网络的机械化学分裂程度。二氧化碳调节、力触发的机械团激活将与随后的交联聚合耦合，以响应变形加强和重塑材料。该系统将用于确定控制机械团活化和动力学的结构-性质关系，这可能为基础和应用研究中的机械化学研究提供新的策略。项目的教育和外联部分包括：1)加强本科教育和培训；2)丰富研究生专业发展；3)建设科研基础设施，加强教育人才培养。第一个领域包括为参加PUI的不同背景的本科生提供指导研究机会，为参加聚合物技术选修课的本科生开发实践模块和职业模块，并举办研讨会，帮助本科生提交有竞争力的奖学金项目申请。第二个领域包括接待两名有兴趣在PUI追求职业生涯的访问研究生，以获得在PUI进行研究的第一手经验，并开始建立开发本科生驱动的研究项目所需的技能。第三个领域的重点是开发和传播材料，以未来的和新的教师在PUIs帮助他们进行和资助他们的研究。该奖项反映了美国国家科学基金会的法定使命，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。

NON-TECHNICAL SUMMARY:In nature, biological systems can constructively respond to mechanical force, such as the healing of skin after a cut. Taking this as inspiration, this project aims to develop force-responsive synthetic polymeric materials that can remodel after force is applied. The goal is to externally regulate the extent of force-triggered activation and remodeling using carbon dioxide as an external stimulus. To do this, the material will include two components. One component is designed to respond to carbon dioxide by swelling and the other includes force-sensitive groups called mechanophores, which will remodel the material in response to the extent of swelling. Using this approach, the project describes systematic studies examining the structure-property relationships that underlie mechanophore activation and their time scales in polymer networks. This project will help advance research towards developing materials offering enhanced safety, longer lifespan, and reduced environmental impact. The project will also include educational and outreach activities including mentored research opportunities for undergraduates from diverse backgrounds attending a primarily undergraduate institution (PUI), the development of a hands-on module based on this project for a technical elective in polymers, and the implementation of a career module to expose students to career paths in the field. Further, this project supports hosting two visiting graduate students who have interest in a career at a PUI for the summer to begin building the skills needed to develop an undergraduate-driven research program.TECHNICAL SUMMARY:The ability of biological systems to respond constructively to mechanical force inspires the design of mechano-responsive polymer networks that similarly elicit constructive responses. However, strategies to develop synthetic materials capable of force-triggered remodeling remain limited. This effort will take a stepwise approach towards regulating mechanochemical activation using an external stimulus in double network (DN) hydrogels. Using a DN structure, external control will be afforded by a carbon dioxide (CO2)-responsive primary network, which regulates the extent of mechanochemical scission in the secondary network via swelling. CO2-regulated, force-triggered activation of the mechanophore will be coupled to a subsequent crosslinking polymerization to strengthen and remodel the material in response to deformation. This system will be used to determine the structure-property relationships that govern mechanophore activation and kinetics, which may enable new strategies to study mechanochemistry in basic and applied research.Educational and outreach components of the project include: 1) enhancing undergraduate education and training; 2) enriching graduate professional development; and 3) building research infrastructure and enhancing educator development. The first area includes providing mentored research opportunities for undergraduates of diverse backgrounds attending a PUI, development of a hands-on module and career module targeted towards undergraduates enrolled in a technical elective focused on polymers, and hosting a workshop to aid undergraduates in submitting competitive applications to a fellowship program. The second area includes hosting two visiting graduate students who have interest in pursuing a career at a PUI for the summer to gain first-hand experience of conducting research at a PUI and to begin building the skills needed to develop an undergraduate-driven research program. The third area focuses on developing and disseminating materials to prospective and new faculty at PUIs to help them perform and fund their research.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.