Covalent Polymer Mechanochemistry

通过这个奖项，大分子、超分子和纳米化学项目资助杜克大学的斯蒂芬·克雷格教授研究共价聚合物的机械化学。这个项目涉及研究被施加的机械力加速的化学反应。这些反应影响了材料设计的多个方面，包括当前聚合物材料的宏观失效和机械限制。此外，机械响应官能团可能成为新型应力响应和自修复聚合物材料的关键元素。这些研究将深入了解聚合物在使用过程中所经历的宏观机械力如何有效地转化为所需的化学反应，为新型聚合物的开发奠定基础。更广泛的影响来自：(1)通过新的主动学习模块和相关的化学导论实验室经验，以及通过耦合的研究经验，将研究和教育结合起来；(2)在科学界出现不成比例的人员流失之前，通过吸引和招募年轻科学家来扩大代表性不足群体的参与；(3)广泛传播研究成果；(4)探索材料中的分子行为，这将对聚合物化学、物理有机化学、自修复和应力响应材料产生影响。总体技术目标是通过采用最先进的物理测量和开发新的定量方法，为机械化学动力学奠定定量基础。研究计划包括直接、实验表征和定量机械力对沿拉伸聚合物骨架引发的共价反应的影响。因为机械力不同于传统形式的能量输入，如热或光，是定向的，机械力和反应性之间的耦合提供了对过渡态结构的见解。然而，尽管力对化学反应的影响很重要，但对它的定量测量却很少。提出的工作利用了两种新的方法来量化机械化学反应性：多机械团，不可剪切聚合物的单分子力谱，以及多机械团，可剪切聚合物的脉冲超声和分子量降解。所观察到的机械化学活性的模型有望对这两类机械团的反应性进行定量评估。

With this award the Macromolecular, Supramolecular and Nanochemistry Program is funding Professor Stephen Craig of Duke Unviersity to study covalent polymer mechanochemistry. This project involves the study of chemical reactions that are accelerated by an applied mechanical force. These reactions impact multiple aspects of materials design, including the macroscopic failure and mechanical limitations of current polymeric materials. In addition, mechanically responsive functional groups might serve as the critical elements in new stress-responsive and self-healing polymeric materials. These studies will provide insight into how the macroscopic mechanical forces experienced by polymers during use can be effectively channeled into desired chemical responses, providing a foundation for new classes of polymers. Broader impacts come from: (1) integration of research and education through new active learning modules and associated laboratory experiences in introductory chemistry and through coupled research experiences; (2) broadening the participation of underrepresented groups by engaging and recruiting young scientists before the onset of disproportionate attrition from the sciences; (3) disseminating the results of the research broadly; and, (4) probing molecular behavior in materials in a manner that will have an impact on polymer chemistry, physical organic chemistry, and self-healing and stress-responsive materials.The overarching technical objective is to lay a quantitative foundation for mechanochemical kinetics by employing state-of-the-art physical measurements and developing new methods for quantitation. The research plan includes the direct, experimental characterization and quantification of the effect of mechanical forces on covalent reactions triggered along overstretched polymer backbones. Because mechanical force, unlike conventional forms of energy input such as heat or light, is directional, the coupling between mechanical force and reactivity provides insights into the structure of transition states. Despite its importance, however, quantitative measures of the effect of force on chemical reactions are rare. The proposed work makes use of two novel approaches to quantifying mechanochemical reactivity: the single molecule force spectroscopy of multi-mechanophore, non-scissile polymers, and the pulsed sonication and molecular weight degradation of multi-mechanophore, scissile polymers. Models for the observed mechanochemical activity are expected to enable quantitative assessment of reactivity in both classes of mechanophores.