Two-way shape-memory polymer design based on periodic dynamic crosslinks inducing supramolecular nanostructures

第一部分：形状记忆聚合物（SMP）具有许多潜在的应用，包括航空航天、生物医学、软机器人等。目前SMP的局限性包括低能量密度，这意味着材料不能承受大载荷。此外，它们不具有高鲁棒性并且具有差的可逆性。PI的工作通过应变诱导的超分子组装形成的长程有序纳米结构的新机制解决了SMP的局限性。PI和她的团队将通过了解新型材料设计和双向SMP（2 WSMP）设计特定的结构-性能关系来推进材料化学和聚合物科学的知识状态。通过整合合成，加工和先进的表征，他们的目标是使新一代的2 WSMP具有前所未有的能量密度，由低成本和可扩展的商业起始化学品合成。与目前广泛使用的液晶弹性体形状致动材料相比，这些2 WSMP将以低得多的材料成本在大得多的载荷下致动。这将允许更广泛的测试和采用，并有助于推进软执行器的研究。 从该项目中产生的精心策划的高质量实验数据集的集合可以用于基准理论和模拟模型。随着2 WSMP行为的潜在应用和视觉效果，这项工作也为招募和培训学生作为下一代劳动力和研究领导者提供了有吸引力的机会。 第二部分：通过动态非共价键或共价键形成的聚合物网络表现出一系列令人感兴趣的和可调的机械性能（例如，坚韧、有弹性、可自愈、刺激响应和可重新配置）。在自然界中，等级有序结构是通过弱但合作的相互作用形成的，以执行精确的功能。本工作将探讨一种新的高能量密度形状记忆聚合物的分子设计概念，通过应变诱导形成超分子纳米结构的大范围秩序。假设在周期性动态聚合物（PDPs）中形成应变诱导的超分子结构的能力可以通过非共价和共价交联在大应变下稳定聚合物链排列，并且因此在制备的双向形状记忆聚合物（2 WSMP）中微晶排列。 计划的工作将集中在解决有关分子设计，聚合物薄膜和纤维形态控制和结晶域取向的基本问题，并最终对SMP行为的新设计的影响。该研究将导致从低成本和可扩展的试剂合成高能量密度的2 WSMPs。所得到的2 WSMP旨在具有高冲程、在大负载下的致动以及最小的循环滞后。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。

PART 1: NON-TECHNICAL SUMMARY Shape memory polymers (SMPs) have many potential applications, including aerospace, biomedical, soft robotics, and others. Current limitations of SMPs including low energy density, which means the material cannot be subjected to a large load. Furthermore, they do not have high robustness and have poor reversibility. The PI's work addresses limitations of SMPs through a new mechanism of strain-induced long-range ordered nanostructures formed from supramolecular assembly. The PI and her group will advance the state of knowledge in materials chemistry and polymer science through understanding novel materials design and structure-property relationships specific to two-way SMP (2WSMP) design. By integrating synthesis, processing, and advanced characterization, they will aim to enable a new generation of 2WSMPs with unprecedented energy densities synthesized from low-cost and scalable commercial starting chemicals. Compared to current widely used liquid-crystal elastomer shape-actuation materials, these 2WSMPs would actuate under much larger loads at a much lower material cost. This should allow more widespread testing and adoption, and help advance research on soft actuators. The collection of curated, high-quality experimental datasets produced from this project can potentially be used to benchmark theory and simulation models. With the potential applications and visual effects of 2WSMP behaviors, this work also offers appealing opportunities for recruiting and training students as next-generation workforce and research leaders. PART 2: TECHNICAL SUMMARY Polymer networks formed through dynamic noncovalent or covalent bonds exhibit a range of interesting and tunable mechanical properties (e.g., tough, elastic, self-healable, stimuli-responsive, and reconfigurable). In nature, hierarchically ordered structures are formed through weak but cooperative interactions to perform precise functions. This work will investigate a new molecular design concept of high energy-density shape memory polymers through strain-induced large range order of supramolecular nanostructure formation. The hypothesis is that the ability to form strain-induced supramolecular structures in periodic dynamic polymers (PDPs) may stabilize polymer chain alignment under large strains through non-covalent and covalent crosslinks and as a result crystallite alignment in the prepared two-way shape memory polymers (2WSMPs). The planned work will focus on addressing fundamental questions related to molecular design, polymer thin film and fiber morphology control and crystalline domain orientation, and ultimately their impact on the new designs of SMP behaviors. This study will lead to high energy density 2WSMPs synthesized from low cost and scalable reagents. The resulting 2WSMPs are aimed to have high stroke, actuation under large loads, and minimal cycling hysteresis..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.