Exploring room temperature dynamic covalent bonds in adaptive materials

第1部分：非技术概述聚合物/塑料在我们日常生活的几乎每一个方面都扮演着重要的角色。一般来说，大多数日常使用的塑料都是被动的，即为单一目的(如食品容器、塑料袋或粘合剂)而设计的，一旦使用，这些塑料就会被丢弃并影响环境。该项目致力于开发一类能够根据需要治愈或改变形状的自适应聚合物。此外，这些材料具有在使用后进行再加工的能力，并且通过控制在再加工过程中使用的温度和时间，有可能定制它们的物理特性(例如，硬度、弹性、温度响应)。精确调整材料性能的能力打开了定向材料的大门，这些材料可以通过加工轻松而系统地改变，这反过来又扩大了它们可以用于的潜在应用领域。这项研究混合了聚合物领域内的不同学科，从化学到聚合物加工和机械表征。重要的是，这种广泛的研究方法为学生(在所有级别)提供了涵盖这一主题的广泛的教育经验。研究生将参加一个为期两年的外展培训计划，以发展和完善他们与公众互动和有效沟通的能力。利用这项培训，他们将参加一系列的外联活动，包括少年科学咖啡馆S、非小物质分子工程博览会，以及旨在接触芝加哥当地公立学校学生的一系列计划。这些外展活动，再加上高中和本科综合研究机会，旨在增加在科学和工程领域任职人数不足的少数群体的比例。第2部分：技术综述：Rowan团队最近的工作表明，室温动态Thia-Michael(TM)化学(基于苯氰基乙酸酯/酰胺Michael受体)可以通过一种称为动态反应诱导相分离(DIPS)的过程来获得机械强度高的聚合物网络。这些相分离的动态材料表现出诸如愈合、形状记忆和可逆粘合等性能。此外，TM反应的交换动力学和热力学可以通过TM受体的电子性质来系统地改变，从而可以研究动态交换性质如何影响网络的相分离形态和整体材料性质。计划中的研究通过退火条件、光照曝光以及与其他动态键合系统的交叉反应来研究动态TM材料的操作。此外，这些材料的相分离形态(以及因此的机械性能)可以通过热加工条件(冷却速度、退火步骤等)直接控制。因此，这项工作的第一个目标是发展这类自适应材料的基本结构/加工/形态/性能关系。这项工作的第二个目标是利用苯氰乙酸酯/酰胺Michael受体结构固有的E/Z异构性来开发光敏动态TM键，从而获得一类新型的光激活动态材料。最后，将启动一项新计划，旨在使用系统聚合物科学方法(受系统化学启发)进行功能性聚合物设计，目标是获得多功能聚合物，即其性能在暴露于化学或环境线索后可显著改变的聚合物系统，使其可用于各种应用。为此，PI将调查将多个通信动态反应周期整合到聚合物网络中的可能性。该奖项反映了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。

PART 1: NON-TECHNICAL SUMMARY Polymers/plastics play a critical role in almost every aspect of our daily life. Generally, most plastics in everyday use are passive, that is, designed for a single purpose (e.g., food containers, plastic bags, or adhesives) and once used these plastics are thrown away and impact the environment. This project is focused on developing a class of adaptive polymers that have the ability to heal or change shape on demand. In addition, these materials have the ability to be reprocessed after use, and by controlling the temperature and time employed during reprocessing it is possible to tailor their physical properties (e.g., stiffness, elasticity, temperature response). The ability to precisely retool the material properties opens the door to targeting materials that can be easily and systematically changed by processing, which in turn expands the potential applications areas that they can be used for. The research is a mix of different disciplines within the polymer area, from chemistry to polymer processing and mechanical characterization. Importantly, this broad research approach provides students (at all levels) with wide-ranging educational experiences covering this swath of topics. Graduate students will participate in a two-year outreach training program to develop and refine their abilities to engage and effectively communicate with the general public. Using this training they will participate in a series of outreach events, including Junior Science Cafés, the No Small Matter Molecular Engineering Fair, as well as a number of programs aimed at outreach to students from local Chicago public schools. These outreach activities, in conjunction with additional integrated high-school and undergraduate research opportunities, are designed to increase the fraction of underrepresented minorities in science and engineering. PART 2: TECHNICAL SUMMARY Recent work by the Rowan group has shown that room temperature dynamic thia-Michael (tM) chemistry (based on benzalcyanoacetate/amide Michael acceptors) can be used to access mechanically robust polymer networks through a process coined dynamic reaction-induced phase separation (DRIPS). These phase separated dynamic materials exhibit properties such as healing, shape memory, and reversible adhesion. Furthermore, the exchange kinetics and thermodynamics of tM reactions can be systematically altered by the electronic nature of the tM acceptor, allowing an investigation of how the dynamic exchange properties impact both the phase-separated morphology and the overall materials properties of the network. The planned research investigates the manipulation of dynamic tM materials through annealing conditions, light exposure, and cross-reactivity with additional dynamic bonding systems. In addition, the phase separated morphology (and therefore mechanical properties) of these materials can be directly manipulated through thermal processing conditions (cooling rates, annealing steps, etc.). As such, the first goal of this work is aimed at developing fundamental structure / processing / morphology / property relationships in this class of adaptive materials. The second goal of this work is to develop photo-responsive dynamic tM bonds by taking advantage of the inherent E/Z isomerism of the benzalcyanoacetate/amide Michael acceptor structure, to give access to a new class of photo-activated dynamic materials. Finally, a new program will be initiated aimed at using a Systems Polymer Science approach (inspired by systems chemistry) to functional polymer design with the goal of accessing pluripotent polymers, namely polymer systems whose properties can be significantly altered upon exposure to chemical or environmental cues allowing them to be used in a wide variety of applications. To do this, the PI will investigate the potential of incorporating multiple communicating dynamic reaction cycles into polymer networks..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.