Architectural design of active adhesives

粘合剂是一种无处不在的材料，不仅在我们的日常生活中，而且在先进和专业的应用中，如可穿戴电子产品，生物医学粘合剂和软机器人。目前满足这种多样化功能的方法依赖于探索性地将各种聚合物与大量需要的增粘剂、增塑剂和其他添加剂混合在一起。这种以混合为基础的财产控制方法是无效和不精确的。此外，松散的添加剂容易浸出和迁移，这会导致性能随时间的变化以及不可避免的表面污染，从而禁止它们在敏感应用中使用，如艺术品修复，生物医学设备和微电子。拟议的按架构粘合平台将使无添加剂粘合剂的设计具有定制的属性组合，可以根据需要切换。该平台基于带有动态分子连接剂的刷状聚合物网络，为分子支架重构提供了多种途径，同时又不损失材料的完整性。分子电刷网络中丰富的结构参数允许独立于化学成分和彼此的不同物理特性的可编程变化。开发具有主动调制性能的结构可编程粘合剂将为软物质工程提供突破，产生具有特殊性能组合和按需切换能力的活性粘合剂。先进材料的设计将通过精密化学、软物质物理和新兴技术的整合，为不同背景的研究生提供充分的跨学科培训机会。第2部分：技术概述粘合剂性能是由体积和界面变形机制相互作用的结果，两者本质上都是粘弹性的。理解分子刷结构如何控制这种相互作用代表了本提案的智力焦点。拟议的研究将解决以下基本问题。首先是粘附与分子网络结构之间的层次关系，跨越不同的长度和时间尺度。了解刷子结构的单个元素如何影响粘弹性响应是实现压敏胶（psa）性能可编程控制的重要里程碑。第二是附着力对化学成分的内在依赖，以及不同的附着力特性（如粘性、拉伸和附着力）的相互依赖。按结构设计的方法将打破这些传统规则，允许独立于化学和彼此的物理特性的变化。第三是目前无法在不影响设备完整性和形状的情况下根据需要切换压敏胶粘剂材料的粘附强度。这一挑战将通过战略性地整合休眠功能来解决，这些功能可以通过外部刺激激活，从而触发网络拓扑结构的内部重新排列。该奖项反映了NSF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 SUMMARYAdhesives are ubiquitous materials not only in our daily lives but also for advanced and specialized applications such as wearable electronics, biomedical adhesives, and soft robotics. Current approaches to meet such a diverse scope of functions rely on exploratively blending assorted polymers with large quantities of tackifiers, plasticizers and other additives as needed. This mixing-based approach toward property control is ineffective and imprecise. Furthermore, loose additives are prone to leaching and migration, which leads to property variation over time along with inevitable surface contamination, thus prohibiting their use in sensitive applications such as art restoration, biomedical devices, and microelectronics. The proposed adhesion-by-architecture platform will empower the design of additive-free adhesives with tailored property combinations that can be switched on demand. The platform is based on brush-like polymer networks with dynamic molecular linkers, which provide various pathways for molecular-scaffold reconfiguration without losing material integrity. The abundance of structural parameters in molecular brush networks allows for the programmable variation of distinct physical characteristics independent of chemical composition and one another. Developing structurally programmable adhesives with actively modulated performance will offer a breakthrough in soft matter engineering, yielding active adhesives with exceptional property combinations and switching on-demand capability. The design of advanced materials will provide ample opportunities for interdisciplinary training of graduate students with diverse backgrounds through integration of precision chemistry, soft-matter physics, and emerging technologies.PART 2: TECHNICAL SUMMARYAdhesive performance results from an interplay of bulk and interfacial deformation mechanisms, both viscoelastic in nature. Understanding how molecular brush architecture controls this interplay represents the intellectual focus of this proposal. The proposed research will address the following fundamental problems. The first is the hierarchical relationship between adhesion and molecular network architecture, spanning different length and time scales. Understanding how an individual element of the brush structure contributes to the viscoelastic response is a crucial milestone towards programmable control of the performance of pressure-sensitive adhesives (PSAs). The second is the inherent reliance of adhesion on chemical composition and the interdependence of distinct adhesive characteristics such as tack, stretch, and work of adhesion. The design-by-architecture approach will allow breaking these conventional rules to allow for the variation of physical characteristics independent of chemistry and one another. The third is the current inability to switch the adhesion strength of pressure-sensitive adhesive materials on demand without perturbing the integrity and shape of a device. This challenge will be addressed by strategically incorporating dormant functionalities that can be activated by an external stimulus to trigger internal rearrangement of the network topology..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.