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

非技术摘要：在自然界中，生物系统可以建设性地对机械力做出反应，例如割伤后皮肤的愈合。受此启发，该项目旨在开发力响应型合成聚合物材料，这种材料可以在受力后进行重塑。其目标是使用二氧化碳作为外部刺激，从外部调节力量触发的激活和重塑的程度。要做到这一点，材料将包括两个组件。一个组件旨在通过膨胀对二氧化碳做出反应，另一个组件包括被称为机械团的力敏感基团，它将根据膨胀的程度对材料进行重塑。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载体激活及其时间尺度所依据的结构-性质关系。该项目将有助于推动研究，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外展活动，包括为来自不同背景的本科生在一个主要是本科院校(PUI)学习的本科生提供指导研究机会，在此项目的基础上为聚合物技术选修课开发一个动手模块，以及实施一个职业模块，让学生了解该领域的职业道路。此外，该项目支持招待两名有兴趣在PUI工作的来访研究生，开始培养开发本科生驱动的研究计划所需的技能。技术摘要：生物系统对机械力做出建设性反应的能力激发了机械响应聚合物网络的设计，同样引起了建设性的反应。然而，开发能够力触发重塑的合成材料的策略仍然有限。这项工作将采取一种循序渐进的方法，在双网络水凝胶中使用外部刺激来调节机械力化学激活。使用DN结构，外部控制将由二氧化碳(CO2)响应的一级网络提供，该一级网络通过膨胀调节二级网络中机械力化学断裂的程度。二氧化碳调节的、力触发的机械团的激活将与随后的交联化聚合相耦合，以加强和重塑材料，以响应变形。这个系统将被用来确定支配机械团激活和动力学的结构-性质关系，这可能使在基础和应用研究中研究机械力化学的新战略成为可能。该项目的教育和推广部分包括：1)加强本科生教育和培训；2)丰富研究生专业发展；3)建设研究基础设施和加强教育者发展。第一个领域包括为参加PPI的不同背景的本科生提供有指导的研究机会，开发一个针对就读聚合物技术选修课的本科生的动手模块和职业模块，以及举办一个研讨会，帮助本科生向奖学金计划提交竞争性申请。第二个领域包括招待两名有兴趣在PUI从事职业生涯的来访研究生，以获得在PPI进行研究的第一手经验，并开始培养开发以本科生为导向的研究计划所需的技能。第三个领域专注于开发和传播材料给PUIS的未来和新教师，以帮助他们进行研究并为他们的研究提供资金。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: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.