Mechanistic Design and Understanding of Fully Polymeric Antifreezing and Tough Hydrogels

结冰是一种自然现象，在维持地球上的生命方面起着至关重要的作用，但不必要的结冰会导致严重的经济，环境和生命威胁后果。传统的防冻材料，如疏冰无水有机物或含有防冻添加剂的亲水性水凝胶，在零度以下的温度下经常遭受弱的机械性能，这限制了它们的实际应用。为了解决这个问题，本研究将探索一种设计策略，用于开发一类新的完全聚合的水凝胶，该水凝胶具有固有的防冻性能和增强的机械强度，而不需要防冻添加剂。 一个成功的项目可以为一个新的防冻水凝胶家族铺平道路，这些水凝胶具有不同的结构和其他内置功能，适用于零度以下的不同应用，包括柔性超级电容器，软机器人，电子皮肤和可穿戴设备。该研究是多学科的，将为高分子化学/物理、分子模拟和工程设计领域的本科生/研究生和高中教师提供宝贵的学习经验。此外，PI还将在课程中引入实验和计算部分，以加强学生对工程材料的学习，并通过组织国际会议，特别期刊和STEM学生活动来促进水凝胶材料领域。技术总结：本研究的总体目标是双重的，旨在（1）开发和设计一种新的具有内在防冻和增强机械性能的全聚合水凝胶系列，以及（2）通过使用聚合物化学和分子模拟的组合，在从原子到宏观水平的不同空间和时间尺度上对这些水凝胶的防冻/增韧机制进行基本了解。这些防冻水凝胶的设计策略是将强水结合聚合物与紧密交联和高度互穿的双网络结构整合，从而增强聚合物-水相互作用以竞争性地抑制冰成核和生长，以及激活多个能量耗散途径以改善水凝胶的机械性能。与实验工作平行，将开发具有新聚合算法的多尺度分子模拟，以研究在静止和拉伸状态以及不同零度以下温度下限制在网络中的聚合物周围的水结构，动力学和相互作用。计算研究可以揭示不同的，但相关的防冻和增韧机制在原子水平上。最后，将比较和关联来自基准水凝胶系统的实验和计算数据，以更好地理解此类水凝胶的复杂组成/结构依赖性防冻和机械性能。这将导致以迭代的方式通过研究聚合物化学，侧基/交联剂，网络结构和水行为的变化来优化防冻水凝胶的设计。总的来说，具有增强性能的新型防冻水凝胶的开发可能会影响提高能源效率、环境保护、生物医学治疗和工业应用等领域。该奖项反映了NSF的法定使命，并被认为是值得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的支持。

NON-TECHNICAL SUMMARY:Icing is a natural phenomenon that plays a crucial role in sustaining life on Earth, but unwanted icing can cause severe economic, environmental, and life-threatening consequences. Conventional antifreezing materials, such as icephobic water-free organics or hydrophilic hydrogels containing antifreezing additives, often suffer from weak mechanical properties under subzero temperatures, which limits their practical applications. To address this issue, this research will explore a design strategy for developing a new class of fully polymeric hydrogels that possess inherent antifreezing properties and enhanced mechanical strength without requiring antifreeze additives. A successful project could pave the way for a new family of antifreezing hydrogels with diverse structures and other built-in functions for different applications under subzero temperatures, including flexible supercapacitors, soft robotics, electronic skin, and wearable devices. The research is multi-disciplinary and will provide a valuable learning experience for undergraduate/graduate students and high-school teachers in the areas of polymer chemistry/physics, molecular simulations, and engineering design. Additionally, the PI will also introduce experimental and computational components to the curriculum to enhance student learning of engineered materials and promote the field of hydrogel-based materials by organizing international conferences, special journal issues, and STEM student activities. TECHNICAL SUMMARY:The overarching goals of this research are twofold and aim to (1) develop and engineer a new family of fully polymeric hydrogels with intrinsic antifreezing and enhanced mechanical properties and (2) gain a fundamental understanding of antifreezing/toughening mechanisms of these hydrogels at different spatial and time scales ranging from atomic to macroscopic levels by using a combination of polymer chemistry and molecular simulations. The design strategy for these antifreezing hydrogels is to integrate strong water-binding polymers with tightly crosslinked and highly interpenetrating double-network structures, allowing to enhance polymer-water interactions for competitively inhibiting ice nucleation and growth, as well as to activate multiple energy-dissipation pathways for improving hydrogel mechanical properties. Parallel to experimental works, multiscale molecular simulations with new polymerization algorithms will be developed to study water structures, dynamics, and interactions around polymers confined in networks at both resting and stretching states, as well as at different subzero temperatures. Computational study allows to reveal different but correlated antifreezing and toughening mechanisms at atomic levels. Finally, experimental and computational data from the benchmarking hydrogel systems will be compared and correlated to better understand the complex composition/structure-dependent antifreezing and mechanical performance of such hydrogels. This will lead toward an optimal design of antifreezing hydrogels in an iterative way by investigating changes in polymer chemistries, pendant groups/crosslinkers, network structures, and water behavior. Overall, the development of new antifreezing hydrogels with enhanced properties could impact areas such as improved energy efficiency, environmental protection, biomedical treatments, and industrial applications..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.