Mechanistic Design and Understanding of Fully Polymeric Antifreezing and Tough Hydrogels

非技术摘要：结冰是一种自然现象，对维持地球上的生命起着至关重要的作用，但不受欢迎的结冰可能会造成严重的经济、环境和危及生命的后果。传统的防冻材料，如含防冻剂的疏水性有机物或亲水性水凝胶，往往在零下温度下力学性能较差，限制了它们的实际应用。为了解决这一问题，本研究将探索一种设计策略，以开发一种新型的全聚合水凝胶，具有固有的防冻性能和增强的机械强度，而不需要防冻剂。一个成功的项目可能会为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，可用于零下温度下的不同应用，包括柔性超级电容器、软机器人、电子皮肤和可穿戴设备。这项研究是多学科的，将为本科生/研究生和高中教师在聚合物化学/物理、分子模拟和工程设计领域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、特刊和STEM学生活动来促进水凝胶材料领域的发展。技术概述：这项研究的主要目标是双重的，目的是(1)开发和设计具有内在防冻和增强力学性能的新的全聚合物水凝胶家族；(2)利用聚合物化学和分子模拟相结合的方法，在从原子到宏观的不同空间和时间尺度上对这些水凝胶的防冻/增韧机理有一个基本的了解。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相结合，从而增强聚合物-水的相互作用，以竞争性地抑制冰核和生长，并激活多条能量耗散途径，以改善水凝胶的力学性能。与实验工作平行的是，将利用新的聚合算法开发多尺度分子模拟，以研究在静止和拉伸状态以及不同零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。计算研究可以揭示原子水平上不同但相互关联的抗冻和增韧机制。最后，将对基准水凝胶系统的实验和计算数据进行比较和关联，以更好地了解此类水凝胶的复杂组成/结构相关的防冻和机械性能。这将通过研究聚合物化学成分、侧基/交联剂、网络结构和水行为的变化，以迭代的方式导致防冻水凝胶的优化设计。总体而言，具有增强性能的新型防冻水凝胶的开发可能会对提高能源效率、环境保护、生物医学治疗和工业应用等领域产生影响。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

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.