Stretchable, Tough, Water-Retaining Hydrogels for Non-Traditional Applications

适用于非传统应用的可拉伸、坚韧、保水水凝胶

• 批准号: 1404653
• 负责人: Joost Vlassak
• 金额: $ 40万
• 依托单位: Harvard University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-05-01 至 2017-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1404653&HistoricalAwards=false
• 关键词: Stretchable; Tough; Water; Retaining; Hydrogels

A three-dimensional polymer network may absorb a large quantity of water and form a hydrogel. Familiar examples include jello and superabsorbent diapers. Hydrogels are under intense development for biomedical applications such as scaffolds in tissue engineering and carriers for drug delivery. Most existing hydrogels, however, are weak, brittle, and not very stretchable. They also dry out as water evaporates. These issues have severely limited the scope of applications of hydrogels. This project will develop stretchable, tough, and water-retaining hydrogels. Hydrogels of enhanced mechanical properties and environmental stability will open new applications. Examples include stretchable, transparent, ionic conductors; fire-retarding blankets; swellable seals; and environmentally responsive actuators and sensors. Large-scale use of hydrogels is attractive for a number of reasons. Many kinds of polymers can form hydrogels; this diversity enables suitable polymers to be selected to achieve specific functions. Hydrogels consist mostly of water, and can be formed by naturally occurring polymers; many hydrogels are inexpensive and environmentally friendly. The mechanical behavior of hydrogels will also serve as a vehicle to bridge the gap between research and education: Fresh insights that arise from this project will be incorporated into graduate courses; the project will offer research opportunities to high-school students, and will use Internet sites such as iMechanica and YouTube to bring recent developments in the mechanics of materials to readers worldwide.Recent findings highlight a significant opportunity: hydrogels of enhanced properties may achieve much broader applications, well beyond those envisaged so far. This opportunity poses new scientific questions concerning the development of stretchable, tough, water-retaining hydrogels. The project will draw upon concepts of nonlinear fracture mechanics, as well as polymer science, to investigate the mechanisms that control multiple mechanical properties of hydrogels, including stretchability, stiffness, strength and toughness. The project will examine approaches that enhance the mechanical properties and environmental stability of hydrogels, by introducing energy dissipation mechanisms to toughen hydrogels, by embedding fibers to stiffen and strengthen hydrogels, by modifying weak bonds to enable healing after deformation, and by adding hygroscopic components to alter the chemical potential of water inside the gels. Energy-dissipation mechanisms of two broad types will be investigated: recoverable dissociation of weak crosslinks such as ionic bonds and crystallites, and frictional sliding between hydrogels and embedded fibers.

三维聚合物网络可以吸收大量的水，形成水凝胶。熟悉的例子包括果冻和高吸水性尿布。水凝胶在生物医学方面的应用正得到大力发展，如组织工程中的支架和药物输送载体。然而，大多数现有的水凝胶都很脆弱，易碎，而且不太可拉伸。它们也会随着水分的蒸发而变干。这些问题严重限制了水凝胶的应用范围。该项目将开发可拉伸、坚韧、保水的水凝胶。增强机械性能和环境稳定性的水凝胶将开辟新的应用领域。例子包括可拉伸的、透明的离子导体；防火毯;剖海豹;以及对环境敏感的执行器和传感器。水凝胶的大规模使用有很多吸引人的原因。多种聚合物可形成水凝胶；这种多样性可以选择合适的聚合物来实现特定的功能。水凝胶主要由水组成，可以由天然存在的聚合物形成；许多水凝胶既便宜又环保。水凝胶的力学行为也将成为弥合研究和教育之间差距的工具：从这个项目中产生的新见解将被纳入研究生课程；该项目将为高中生提供研究机会，并将利用iMechanica和YouTube等互联网网站向全世界的读者介绍材料力学的最新进展。最近的发现强调了一个重要的机会：性能增强的水凝胶可能会获得更广泛的应用，远远超出目前的设想。这一机遇提出了有关可拉伸、坚韧、保水性水凝胶发展的新的科学问题。该项目将借鉴非线性断裂力学和聚合物科学的概念，研究控制水凝胶多种力学性能的机制，包括拉伸性、刚度、强度和韧性。该项目将研究提高水凝胶机械性能和环境稳定性的方法，包括引入能量耗散机制使水凝胶变韧，通过嵌入纤维使水凝胶变硬和增强，通过修改弱键使变形后能够愈合，以及通过添加吸湿成分来改变凝胶内部水的化学势。两种类型的能量耗散机制将被研究：离子键和晶体等弱交联的可恢复解离，以及水凝胶和嵌入纤维之间的摩擦滑动。