Chemical simulations of stress-activated functional molecules and materials

近年来，人们在开发功能分子和材料体系方面付出了巨大的努力。在许多情况下，这些系统被设计为经历化学反应，这些化学反应响应外部刺激，如光、热或电流，执行机械功。例子包括分子航天飞机和马达、行走塑料和微型致动器。另一种探索较少的替代方法涉及相反的过程，在该过程中，通过对系统施加外部应力来对其进行机械加工，从而引发化学反应。考虑到许多现实世界系统中存在的固有的巨大压力，压力激活系统的开发可能会有显著的好处。例如，有可能开发出响应并适应滑动接触中不断变化的应力以最佳地控制摩擦和磨损的功能性润滑剂、检测基础设施中的损伤的分子应力传感器，甚至是响应于在特定细胞部位吸附时所经历的压力而被激活的药物输送系统。为了开发压力激活的功能系统，有必要了解施加的压力和化学反应之间的关系。拟议的研究将为此目的使用量子化学模拟，并遵循三个综合途径。首先，将开发新的方法，以允许模拟承受应力和应变的真实模型系统。其次，这些技术将与传统的模拟方法一起用于研究分子系统如何响应外部压力。模拟将集中在摩擦化学和机械力化学上，摩擦化学涉及在润滑接触中发生的反应，机械力化学涉及通过拉伸分子系统激活反应。第三，这些结果将被用来建立将分子水平的行为与宏观性质联系起来的预测模型，以指导应力激活功能系统的合理发展。这项工作本身利用了化学、物理、材料科学、应用数学、计算机科学和工程学，这将为五名研究生和两名博士后研究员提供宝贵的跨学科经验。

Recent years have witnessed tremendous efforts aimed at developing functional molecular and materials systems. In many cases, these systems are designed to undergo chemical reactions that perform mechanical work in response to external stimuli such as light, heat, or an electrical current. Examples include molecular shuttles and motors, walking plastics, and microscopic actuators. An alternative, less-explored avenue involves the opposite process in which chemical reactions are induced by performing mechanical work on the system by subjecting it to external stresses. The development of stress-activated systems may have significant benefits given the inherently large stresses present in many real-world systems. For example, it may be possible to develop functional lubricants that respond and adapt to the changing stresses in sliding contacts to optimally control friction and wear, molecular stress sensors that detect damage in infrastructure, and even drug delivery systems that are activated in response to the stresses experienced upon adsorption at specific cellular sites. To develop stress-activated functional systems, it is necessary to understand the relationship between applied stress and chemical reactions. The proposed research will use quantum chemical simulations for this purpose and follow three integrated avenues. First, new methods will be developed to permit simulations of realistic model systems subjected to stresses and strains. Second, these techniques will be used along with conventional simulation methods to study how molecular systems respond to external stresses. The simulations will focus on tribochemistry, which involves reactions occurring in lubricating contacts, and mechanochemistry, which involves the activation of reactions by stretching molecular systems. Third, the results will be used to formulate predictive models relating molecular-level behaviour to macroscopic properties to guide the rational development of stress-activated functional systems. The work itself draws on chemistry, physics, materials science, applied mathematics, computer science, and engineering, which will provide five graduate students and two postdoctoral fellows with valuable interdisciplinary experience.