Polymer Adhesion at Extreme Rates and Temperatures

聚合物粘合剂是聚合物最普遍的应用之一，它们在当今技术中的关键作用只会越来越大。从电子产品到医疗保健，再到建筑和建筑，许多技术对聚合物粘附性的依赖大大增加了这些界面遇到的环境和负载条件的范围。随着聚合物界面在防护装备和机器人设备中发挥更重要的作用，这种环境和条件的范围将会扩大，这些设备专门设计用于最大限度地减少人类暴露于潜在有害的极端环境中。此外，由于聚合物粘附和粘合剂产生的废物数量正在以显着的速度增长。这种废物不仅是直接用于粘合的聚合物，而且是粘合材料，这些材料通常难以分离，以便有效地回收或升级循环。该研究项目将对极端加载速率和温度变化下聚合物界面的粘附性产生新的认识。这一基础将有助于弥补极端条件下聚合物界面特性基础知识的不足，我们预计这些结果将指导分离界面的新协议的开发，从而帮助建立一个更可持续的社会。参与该项目的研究生和本科生将学习广泛的技能，包括聚合物合成和配方，粘附，机械和热性能的表征方法，以及旨在解决技术前沿挑战的定制仪器的开发和实施。他们还将培养写作、管理、指导和演讲技巧。此外，研究团队将启动一项新的K-12外展计划，面向马萨诸塞州西部地区代表性不足的少数民族学生，以帮助激发STEM领域未来的职业发展。虽然聚合物界面强度已经得到了经典的研究，但在材料结构如何控制界面在机械和热载荷下的高速变形方面，开放性问题和看似矛盾的结果仍未得到解决。PI的团队将结合一种新的实验方法，称为功率放大动态力学分析（PADMA），与模型材料相结合，为控制聚合物界面强度提供见解和途径。基于目前广泛用于许多商业粘合剂的聚丙烯酸正丁酯的三种模型聚合物体系将形成研究的基础。设计的两种系统具有相似的低应变和低应变率性能，但大应变和大应变率响应不同。这种差异与神经网络的交联结点有关。这些材料将深入了解弹性粘附长度尺度如何在高速下演变，以及这种变化如何与聚合物网络结构的变化相关。第三种材料体系是控制水体积分数的聚（丙烯酸正丁酯）-共聚（二甲基丙烯酰胺）水凝胶，它将深入了解由高速率热变化引发的局部相变如何改变界面分离。具体来说，在高热率加载时，水膨胀域的大小和连通性将与界面强度的变化有关。总的来说，这些结果将有助于提高聚合物性能的知识基础，特别是在界面方面。这一知识将导致分离聚合物界面的新方法，减少能量，不需要有害溶剂。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。

PART 1: NON-TECHNICAL SUMMARYPolymer adhesives are one of the most pervasive applications of polymers, and their critical role in today’s technologies has only grown. The reliance of numerous technologies, from electronics to medical care to building and construction, on polymer adhesion has vastly increased the range of environments and loading conditions that these interfaces encounter. This range of environments and conditions will grow as polymer interfaces are expected to play more important roles in protective gear and in robotic devices that are specifically designed to minimize human exposure to potentially harmful extremes. Additionally, the quantity of waste that is created due to polymer adhesion and adhesives is growing at significant rates. This waste is not only polymers directly used in bonding but also the bonded materials, which are typically difficult to separate in order to be recycled or upcycled efficiently. This research project will lead to new understanding of adhesion at polymer interfaces at extreme rates of loading and temperature change. This foundation will help to meet a deficiency in the fundamental knowledge of polymer interfacial properties at extreme conditions, and we anticipate that the results will guide the development of new protocols for separating interfaces that help build a more sustainable society. Graduate and undergraduate students who participate in this project will learn a broad range of skills, including polymer synthesis and formulation, characterization methods for adhesion, mechanical and thermal properties, and the development and implementation of custom instrumentation designed to address challenges at the forefront of technology. They will also develop writing, management, mentoring, and presentation skills. Additionally, the team of researchers will launch a new K-12 outreach program geared toward under-represented minority students throughout the Western Massachusetts region to help inspire future careers in STEM. PART 2: TECHNICAL SUMMARYWhile polymer interfacial strength has been studied classically, open questions, and seemingly contradictory results, remain unresolved in how material structure controls the deformation of interfaces loaded, mechanically and thermally, at high rates. The PI's group will combine a new experimental method, called power amplified dynamic mechanical analysis (PADMA), with model materials to provide insight and pathways for controlling polymer interfacial strength. Three model polymer systems based on poly(n-butyl acrylate), which is broadly used in many current commercial adhesives, will form the foundation of the study. Two systems will be designed with similar low strain and low strain rate properties but different large strain and large strain rate responses. This difference will be associated with the network’s crosslink junctions. These materials will provide insight into how the elasto-adhesion length scale evolves at high velocities and how this change is related to changes in the polymer network structure. The third materials system, poly(n-butyl acrylate)-co-poly(dimethylacrylamide) hydrogels with controlled volume fractions of water, will provide insight into how localized phase transitions initiated by high rate thermal changes alter interfacial separation. Specifically, the size and interconnectivity of water swollen domains will be related to changes in interfacial strength when loaded at high thermal rates. Overall, the results will contribute to the limited, yet growing, knowledge base of polymer properties at high rates, especially at interfaces. This knowledge will lead to new methods for separating polymer interfaces with decreased energy and without the need for harmful solvents.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.