Understanding the Mobile Oriented Amorphous Fraction in Semicrystalline Ferroelectric Polymers and Its Unique Contribution to Electrostriction

柔性混合电子产品在各种应用中需求量很大，包括物联网、人体性能监测、可穿戴医疗传感器、能量收集和软机器人。在众多的电活性聚合物中，电致伸缩聚合物表现出许多独特的和吸引人的属性。这个项目采用了一个综合的实验/理论方法来理解极性半结晶聚合物的电致伸缩的基本物理。据建议，液晶类取向的非晶部分有助于显着的电致伸缩驱动。利用这一假设，将实现理论预测，合成和性能表征的闭环，以获得基本的理解并加速新材料的发现。 此外，该项目还将整合科学、技术、工程和数学方面的教育和推广。 这将包括本科生和高中生的暑期研究机会。 技术概要：为了响应柔性电子的快速发展，本项目旨在了解电致伸缩的起源并开发新的电致伸缩聚合物以获得更好的性能。最近，铁电聚合物复杂的半结晶形态中的一种独特成分，即，液晶状取向的无定形部分（OAF）。与铁电晶体不同，这些高度移动的OAF可以通过场诱导的构象转变（即，机械电致伸缩）和对准的铁电畴的电排斥。在这个项目中，计算机模拟与全原子和粗粒度的分子动力学将首先被用来解开机械电致伸缩和电排斥机制，并了解其理论极限。这些信息将指导电致伸缩聚合物的实验制备，包括聚（偏二氟乙烯）为基础的无规共聚物/三元共聚物和松弛样的n-尼龙共聚物。原位X射线衍射在电极化过程中将进行了解复杂的半结晶形态和微分贡献的微晶和OAF。实验结果将反馈到计算机模拟中进行改进。通过计算机模拟、合成、结构/性能表征和反馈的循环，将充分理解铁电聚合物中的增强电致伸缩，并将实现新的电活性材料。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:Flexible hybrid electronics are in high demand for various applications, including the internet of things, human performance monitoring, wearable medical sensors, energy harvesting, and soft robotics. Among the many electroactive polymers, electrostrictive polymers exhibit many unique and appealing attributes. This project incorporates an integrated experimental/theoretical approach to understand the fundamental physics of electrostriction in polar semicrystalline polymers. It is proposed that the liquid-crystal-like oriented amorphous fraction contributes significantly to the electrostrictive actuation. Capitalizing on this hypothesis, a closed loop of theoretical prediction, synthesis, and property characterization will be implemented to obtain fundamental understanding and accelerate the discovery of new materials. In addition, this project will also integrate education and outreach in science, technology, engineering, and mathematics. This will include summer research opportunities for undergraduates and high school students. TECHNICAL SUMMARY:In response to the fast development of flexible electronics, this project aims to understand the origin of electrostriction and develop new electrostrictive polymers for better performance. Recently, a unique component in the complex semicrystalline morphology of ferroelectric polymers, i.e., the liquid-crystal-like oriented amorphous fraction (OAF), was identified. Unlike the ferroelectric crystals, these highly mobile OAFs can actuate at a much lower electric field via a field-induced conformational transformation (i.e., mechanoelectrostriction) and the electric repulsion of aligned ferroelectric domains. In this project, computer simulation with full-atomistic and coarse-grained molecular dynamics will first be used to unravel both the mechanoelectrostriction and the electric repulsion mechanisms and to understand their theoretical limits. This information will guide the experimental preparation of electrostrictive polymers, including both poly(vinylidene fluoride)-based random copolymers/terpolymers and relaxor-like n-nylon copolymers. In-situ X-ray diffraction during electric poling will be performed to understand the complex semicrystalline morphology and differential contributions from the crystallites and the OAFs. The experimental findings will be fed back to the computer simulation for refinement. Through this cycle of computer simulation, synthesis, structure/property characterization, and feedback, enhanced electrostriction in ferroelectric polymers will be fully understood, and new electroactive materials will be implemented..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.