Crystal Isomorphism and Nanodomain Approach toward Novel Ferroelectric Crystalline Polymers

技术综述：在半晶性极性聚合物中观察到了新颖的铁电行为，即窄的单极化和双极化回路，在先进的电子应用中具有广阔的前景。基于聚偏氟乙烯无规共聚物的最新发现，提出了在铁电晶体中具有大体积共单体的重复单元同象是扩大链间距离和钉扎纳米尺寸铁电域(即纳米域)的有效策略。在该方案中，利用晶体同构钉扎纳米结构的假设，合理地设计了新型铁电尼龙共聚物，并对其工作机理进行了验证。首先，将合成尼龙11与各种尼龙共聚单体的无规共聚物，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，在尼龙11无规共聚物中将进一步采用N-或C-甲基化，以扩大链间距，促进更快的偶极转换。第三，在铁电尼龙晶体中，纳米结构域将被物理钉扎(通过较大的共聚单体)或化学钉扎(通过可紫外线交联的共聚单体)，以实现窄的极化环路。如果成功，这项研究不仅将证实钉扎纳米结构域导致新型铁电行为的机制，而且将为各种电活性应用提供更好的聚合物材料。非技术概述：高场响应的电活性聚合物是一种智能软材料，在电能存储、智能驱动器/人工肌肉和能量收集等领域具有极大的吸引力。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。这阻碍了它们在实际应用中的使用，尽管聚合物具有优异的加工性、重量轻和低成本的特点。受最新研究成果的启发，本项目旨在通过合理的聚合物设计、合成和电学性质表征，实现纳米限制效应对半晶极性聚合物的电响应性能的影响。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，上述应用将变得实际可行，造福社会。除了科研活动，该项目还为少数民族和代表性不足的高中生以及本科生和研究生青年专业人员提供了一个广泛的教育和培训平台。在整个拟议的项目中，将实施并强调一个涉及教师、研究生、本科生和高中生的互动反馈教育主题，以提高普通社区对聚合物纳米科学和技术的认识。

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.