CAREER: Mechanics of Active Polymers with Dynamic Molecular Bonding

这项教师早期职业发展（Career）资助将使用综合实验-理论-计算方法来研究动态活性聚合物的机械和界面特性。动态活性聚合物有望从医疗保健到航空航天的众多应用。作为一个显著的例子，适应性液晶弹性体有很大的潜力成为一种变革性的执行器材料，模仿生物肌肉的主要功能（即，保护，驱动，自我修复），这将使人造机器更接近人类的自然能力，同时大大扩展其应用范围。然而，现有的力学理论不能完全适应这些新兴活性聚合物中涉及的新化学、物理和力学之间的复杂耦合。该项目的理论将建立动态分子键与材料能量耗散、机械和界面特性之间的明确联系，这将成为应用驱动的活性聚合物设计和制造的有效工具。这项资助的教育目标是促进学生对工程的兴趣，加强他们对力学概念的学习，并为他们准备应对聚合物工程挑战的关键技能。增强现实辅助的主动学习方法将被开发，以提高学生对复杂概念的理解。每年将举办研讨会，让少数民族高中学生参与液晶弹性体的4D打印。该研究的具体目标是使用适应性液晶弹性体作为材料平台，开发动态活性聚合物的力学理论建模和仿真框架，将具有动态键合的链构型的演变与网络体积和界面特性联系起来，并使用它来生成具有定制能量耗散，驱动和愈合能力的活性结构的新设计。研究目标包括：(1)揭示能量耗散机制；(2)确定应力-应变关系；(3)了解界面焊接动力学；(4)建立功能结构设计的计算平台。以下基本问题将得到回答：(1)为什么液晶弹性体表现出如此非凡的能量耗散，它与材料成分有何关系？(2)当温度相关的链相互作用和动态键同时存在时，它们的应力-应变关系是怎样的？(3)其界面焊接与非晶态网络有何不同？该理论将成为PI未来研究新开发的活性聚合物的结构-性能关系的设计和表征的基石。它也为PI研究不同形式的活性聚合物的制造和加工技术奠定了基础。该奖项反映了美国国家科学基金会的法定使命，并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，被认为值得支持。

This Faculty Early Career Development (CAREER) grant will use an integrated experimental-theoretical-computational approach to study the mechanical and interfacial properties of dynamic active polymers. Dynamic active polymers promise numerous applications ranging from healthcare to aerospace. As a notable example, adaptable liquid-crystal elastomers have the great potential to become a transformative actuator material that mimics the major functions of biological muscle (i.e., protection, actuation, self-healing), which will bring man-made machines closer to the natural capabilities of humans while greatly extending their applications. However, existing mechanics theories cannot fully accommodate the sophisticated coupling among the new chemistry, physics, and mechanics involved in these emerging active polymers. The project's theory will establish a clear connection between the dynamic molecular bonding and material energy dissipation, mechanical, and interfacial properties, which serves as an effective tool for the application-driven design and manufacturing with active polymers. The educational objective of this grant is to promote students' interest in engineering, enhance their learning of mechanics concepts, and prepare them with critical skills to meet the challenges in polymer engineering. Augmented reality-assisted active learning approach will be developed to improve students’ understanding of complex concepts. Annual workshops will be created to engage minority high school students with 4D printing of liquid-crystal elastomers.The specific goal of the research is to use adaptable liquid-crystal elastomers as a material platform to develop a mechanics of dynamic active polymer theoretical modeling and simulation framework that links the evolution of chain configuration with dynamic bonding to the network bulk and interfacial properties and use it to generate new designs of active structures with tailored energy dissipation, actuation, and healing capabilities. The research objectives include: (i) revealing the energy dissipation mechanisms, (ii) determining the stress-strain relationship, (iii) understanding the interfacial welding kinetics, and (iv) establishing a computational platform to design functional structures. The following fundamental questions will be answered: (1) why do liquid-crystal elastomers exhibit such an extraordinary energy dissipation, and how is it related to the material composition? (2) What is their stress-strain relationship when temperature-dependent chain interactions and dynamic bonding are both involved? (3) How is their interfacial welding different from the amorphous networks? The theory will serve as a cornerstone for the PI’s future studies on the design and characterization of structure-property relationships of newly developed active polymers. It also lays the foundation for the PI to investigate different forms of manufacturing and processing technologies of active polymers.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.