Nanoconfined Polymer Ferroelectricity Lei Zhu, Case Western Reserve University, DMR 0907580

1. Nanoconfined Polymer FerroelectricityLei Zhu, Case Western Reserve University, DMR 0907580 Poly(vinylidene fluoride) (PVDF) is a well-known ferroelectric polymer with high dielectric constants (er>10). Application of ferroelectric PVDF for advanced dielectric applications such as high energy density capacitors is very attractive. However, strong cooperative ferroelectricity in PVDF is disadvantageous for such applications. To achieve high energy storage and low loss simultaneously, we propose to confine PVDF ferroelectricity in nanospaces. Similar to homogeneous crystallization, we expect that by confining ferroelectric polymers in nanospaces, dipole moment switching will be substantially delayed to a higher electric field, resulting in simultaneous high energy density and low loss. In this project, we studied anisotropic dielectric properties and electric energy storage in P(VDF-co-hexafluoropropylene) [P(VDF-HFP)] films. We found that crystal orientation the film is extremely important. This research will provide physical insights in nanoconfined polymer ferroelectricity for the high energy density capacitor application. Figure 1. Unipolar D-E loops for (A) the solution-cast, (B) the solution-cast and stretched, (C) the hot-pressed P(VDF-HFP) films. (D) summarizes stored electric energy in P(VDF-HFP) films with different crystal orientations.

2. Nanoconfined Polymer FerroelectricityLei Zhu, Case Western Reserve University, DMR 0907580 Education and Research at All Levels: Ph.D. students: Fangxiao Guan (3rd yr) One REU undergraduate student: Chad Houghton, Pennsylvania State University, Erie Postdoctoral fellow: Dr. Jing Wang (2nd yr) Outreach Plans to Local High Schools The PI plans to work with local high school students and teachers to disseminate his research findings in nanoconfined polymer ferroelectricity. Undergraduate Research The PI plans to host three undergraduate students in his laboratory to work on the proposed project. Figure 2. An REU student, Chad Houghton, from Pennsylvania State University at Erie presented a poster on homogeneous crystallization in polymer nanodroplets obtained in electrospun nanofibers. Mr. Ganji Zhong, a graduate student, served as his direct mentor for research. This research will provide us a novel method to achieve nanodroplets of ferroelectric polymers such as PVDF.