Crystal Isomorphism and Nanodomain Approach toward Novel Ferroelectric Crystalline Polymers

技术概述：在半晶极性聚合物中观察到新的铁电行为，即狭窄的单和双极化环，并有望用于先进的电气应用。基于聚偏氟乙烯基无规共聚物的最新发现，提出了在铁电晶体内具有大体积共聚单体的重复单元同构是扩大链间距离和引脚纳米级铁电畴（即纳米畴）的有效策略。本文利用晶体同构的纳米结构域固定假说，合理设计了新型铁电尼龙共聚物，并验证了其工作机理。首先，将合成尼龙11无规共聚物与各种n-尼龙共聚物，以错配晶体中的酰胺基团，破坏氢键相互作用以增强铁电性。其次，N-或c -甲基化将进一步应用于尼龙11无规共聚物中，以扩大链间距离并促进更快的偶极子开关。第三，纳米结构域将被物理地（由较大的共聚单体）或化学地（由紫外线交联的共聚单体）固定在铁电尼龙晶体中，以实现窄极化环。如果成功，这项研究不仅将证实钉住纳米结构域的机制，而且将为各种电活性应用提供更好的聚合物材料。非技术总结：具有高场响应的电活性聚合物是智能软材料，在电能存储、智能执行器/人造肌肉和能量收集等众多电气应用中具有很高的吸引力。然而，与电活性陶瓷材料相比，目前的电活性聚合物表现出较差的电场响应。尽管聚合物具有优越的可加工性、重量轻和低成本的特点，但这不利于它们在实际应用中的使用。受近期研究成果的启发，本项目旨在通过合理的聚合物设计、合成和电性能表征，实现对半晶极性聚合物电响应性的纳米约束效应。如果成功，这些新型电活性聚合物将能够实现超高电场响应，上述应用将变得切实可行，造福社会。除科研活动外，本项目还为少数民族和弱势群体高中生、本科和研究生青年专业人才提供了广泛的教育和培训平台。一个互动反馈的教育主题，涉及教师，研究生，本科生和高中生，将在整个拟议的项目中实施和强调，以提高一般社区对纳米科学和聚合物技术的认识。

TECHNICAL SUMMARY:Novel ferroelectric behaviors, namely, narrow single and double polarization loops, have been observed in semicrystalline polar polymers and are promising for advanced electrical applications. Based on recent finding from poly(vinylidene fluoride)-based random copolymers, it is proposed that repeating-unit isomorphism having bulky comonomers inside ferroelectric crystals is an effective strategy to expand interchain distance and pin nanosized ferroelectric domains (i.e., nanodomains). In this proposal, the hypothesis of pinned nanodomains via crystal isomorphism is employed to rationally design new ferroelectric nylon copolymers and testify the working mechanism. First, nylon 11 random copolymers with various n-nylon comonomers will be synthesized to mismatch amide groups in the crystal, disrupting hydrogen-bonding interactions for enhanced ferroelectricity. Second, N- or C-methylation will be further employed in nylon 11 random copolymers to expand the interchain distance and facilitate faster dipole switching. Third, nanodomains will be pinned either physically (by larger comonomers) or chemically (by UV-crosslinkable comonomers) in ferroelectric nylon crystals to realize narrow polarization loops. If successful, this study will not only confirm the mechanism of pinned nanodomains responsible for novel ferroelectric behaviors, but also provide better polymeric materials for various electroactive applications.NON-TECHNICAL SUMMARY:Electroactive polymers with high field response are smart soft materials, which are highly attractive for numerous electrical applications in electrical energy storage, smart actuators/artificial muscles, and energy harvesting. However, comparing with electroactive ceramic materials, current electroactive polymers show inferior electric field responses. This impairs their usage in practical applications, despite the superior processability, light weight, and low-cost characteristics for polymers. Stimulated by recent research results, this project aims to realize a nanoconfinement effect on electric responsiveness of semicrystalline polar polymers via rational polymer design, synthesis, and electrical property characterization. If successful, these novel electroactive polymers will be able to achieve ultrahigh electric field responses and the above-mentioned applications will become practically feasible to benefit society. In addition to the scientific research activities, this project also provides a broad education and training platform for minority and under-represented high school students, and undergraduate and graduate young professionals. An interactive feedback educational theme, involving faculty members, graduate students, undergraduates and high school students, will be implemented and emphasized throughout the proposed project to enhance the awareness of nano-science and technology of polymers in the general community.