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

非技术摘要：各种应用对柔性混合电子产品的需求很高，包括物联网、人体表现监测、可穿戴医疗传感器、能量收集和软机器人。在众多电活性聚合物中，电致伸缩聚合物表现出许多独特且吸引人的属性。该项目采用综合实验/理论方法来了解极性半晶聚合物中电致伸缩的基本物理原理。据认为，类液晶取向的非晶部分对电致伸缩驱动有显着贡献。利用这一假设，将实施理论预测、合成和性能表征的闭环，以获得基本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。 这将包括为本科生和高中生提供夏季研究机会。 技术摘要：针对柔性电子器件的快速发展，该项目旨在了解电致伸缩的起源并开发新型电致伸缩聚合物以获得更好的性能。最近，在铁电聚合物的复杂半晶形态中发现了一种独特的成分，即类液晶取向的非晶态部分（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）和排列的铁电域的电排斥在低得多的电场下驱动。在该项目中，将首先使用全原子和粗粒度分子动力学的计算机模拟来阐明机械电致伸缩和电斥力机制，并了解它们的理论极限。该信息将指导电致伸缩聚合物的实验制备，包括聚偏二氟乙烯基无规共聚物/三元共聚物和松弛剂状正尼龙共聚物。将在电极化过程中进行原位 X 射线衍射，以了解复杂的半晶形貌以及微晶和 OAF 的差异贡献。实验结果将反馈到计算机模拟中进行细化。通过计算机模拟、合成、结构/性能表征和反馈的循环，将充分了解铁电聚合物中增强的电致伸缩，并将实施新的电活性材料。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值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: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.