Molecular Understanding and Design of Physically-linked Double Network Hydrogels

虽然聚合物水凝胶作为软湿材料在废水处理、组织工程、药物递送和食品工业中具有广泛的应用，但大多数水凝胶的机械性能较弱，这极大地限制了它们的用途。双网络（DN）水凝胶，由两个对比和互穿的聚合物网络组成，被认为是可能是最坚韧的软材料。目前对DN凝胶从合成方法到增韧机理的认识主要来自于化学交联的DN凝胶，但这些DN凝胶缺乏自恢复和自修复性能。从化学交联的DN凝胶，拟议的工作试图开发一个新的类的物理为基础的DN水凝胶与集成的上级机械，自愈合，自恢复，和机械诱导的光学性能。 化学和物理连接的DN凝胶的系统探索将使更好地理解结构-性能关系和更好地设计具有其他理想性能的下一代坚韧水凝胶。从该项目中获得的新知识和技术也可能导致工程应用，如强大的人工组织，自我修复材料，智能压力响应机器人和损伤控制传感器。该项目将为各级学生提供研究机会，包括代表性不足的学生，并帮助发展聚合物物理，材料化学，分子模拟和工程设计方面的教科书知识和实践技能。该项目还将通过课程开发、暑期实习和当地推广活动整合更广泛的教育方面。技术概要：本项目的主要目标是开发新的物理连接双网络（DN）水凝胶，该水凝胶具有高机械强度、自修复性能和机械诱导发光三种综合性能。通过研究三种类型的物理连接的DN凝胶，有和没有不同的交联剂，PI的小组希望揭示一些基本原则的内在结构之间的结构网络拓扑结构，功能之间的相互作用和两个网络内，结构依赖于增韧，自我修复，和能量耗散机制的结构性能关系。为此，将探讨三项任务：第一项任务是研究第一和第二网络对基于物理的DN凝胶的机械性能的功能作用，并了解不同的网络及其相互作用如何影响可观察到的机械性能。第二个任务是研究DN凝胶的自恢复和自修复性能和机制，同时仍然保持良好的机械性能。在平行的实验任务，计算组件将包括结构，动力学和两个网络和交联剂之间的相互作用的研究。 此外，将开发一个理论模型来描述网络对机械，自我恢复/愈合性能和能量耗散的依赖性。计算和实验结果的结合和比较将有助于建立物理连接的DN凝胶的宏观性能和纳米网络相互作用之间的关系，在不同的时间尺度和长度尺度，最终旨在制定一套规则，合理设计新的坚韧凝胶。

NON-TECHNICAL SUMMARY:While polymer hydrogels as soft-and-wet materials have a wide range of applications for wastewater treatment, tissue engineering, medication delivery, and in the food industry, most hydrogels are mechanically weak which greatly limits their uses. Double network (DN) hydrogels, consisting of two contrasting and interpenetrating polymer networks, are considered as perhaps the toughest soft materials. Current knowledge of DN gels stemming from synthesis methods to toughening mechanisms comes mainly from chemically crosslinked DN gels, but these lack in self-recovery and self-healing properties. Differently from chemically crosslinked DN gels, the proposed work attempts to develop a new class of physically-based DN hydrogels with integrated superior mechanical, self-healing, self-recovery, and mechanically-induced optical properties. Systematic exploration of both chemically- and physically-linked DN gels will enable a better fundamental understanding of structure-property relationships and a better design of next-generation tough hydrogels with other desirable properties. New knowledge and techniques derived from this project may also lead to engineering applications such as robust artificial tissues, self-healing materials, smart stress-responsive robots, and damage-control sensors. The project will provide research opportunities to students at all levels, including underrepresented students, and help develop textbook knowledge and hands-on skills in polymer physics, materials chemistry, molecular simulations, and engineering design. The project will also integrate broader educational aspects via curriculum development, summer internships, and local outreach activities.TECHNICAL SUMMARY:The main objective of this project is to develop new physically-linked double-network (DN) hydrogels with three integrated properties of highly mechanical strength, self-healing properties, and mechanical-induced luminescence. By studying three types of physically-linked DN gels with and without different crosslinkers, the PI's group expects to reveal some fundamental principles about the intrinsic structure-property relationships amongst structural network topologies, functional interactions between and within two networks, and structural dependence on toughening, self-healing, and energy-dissipation mechanisms. To this end three tasks will be explored: The first task is to study the functional role of the first and second networks on mechanical properties of the physically-based DN gels and to understand how different networks and their interactions affect observable mechanical properties. The second task centers on the study of the self-recovery and self-healing properties and mechanisms of the DN gels while still retaining good mechanical properties. In parallel to the experimental tasks, computational components will include the study of structure, dynamics, and interactions between the two networks and crosslinkers. Moreover, a theoretical model will be developed to describe the dependence of networks on mechanical, self-recovery/healing properties, and energy dissipation. Combination and comparison of the computational and experimental results will help to establish a relationship between the macroscopic performance of the physically-linked DN gels and the nanoscopic network interactions at different time-scales and length-scales, eventually aiming to develop a set of rules for rational design of new tough gels.