Anwar Saleem, Asadi Kamal
Max-Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany.
School of Chemical & Materials Engineering, National University of Sciences & Technology, Sector H-12, Islamabad, Pakistan.
ACS Macro Lett. 2019 May 21;8(5):525-529. doi: 10.1021/acsmacrolett.9b00166. Epub 2019 Apr 22.
Despite the realization of ferroelectricity in the δ-phase of poly(vinyleden difluoride) (PVDF) nearly four decades ago, the dynamics of polarization switching has not been studied yet. Here, we unravel the polarization switching mechanism as a one-dimensional process that is nucleated by a 90° rotation of a CH-CF repeat unit, forming a kink with reversed dipole along the polymer chain. The kink subsequently propagates in time, yielding full polarization reversal along the chain while preserving TGTG' chain conformation. We show that the domain wall mobility in δ-phase PVDF is faster than both conventional ferroelectric β-phase PVDF and its copolymers with trifluoroethylene, P(VDF-TrFE). The switching time at infinite electric field for δ-phase PVDF is ten times faster and amounts to 500 ps. Fast switching dynamics combined with the low voltage operation and high thermal stability of polarization make δ-PVDF a suitable candidate for microelectronic applications.
尽管近四十年前就在聚偏二氟乙烯（PVDF）的δ相中实现了铁电性，但极化切换动力学尚未得到研究。在此，我们揭示了极化切换机制是一个一维过程，该过程由CH-CF重复单元的90°旋转成核，沿着聚合物链形成具有反向偶极子的扭结。扭结随后随时间传播，沿链产生完全极化反转，同时保持TGTG'链构象。我们表明，δ相PVDF中的畴壁迁移率比传统铁电β相PVDF及其与三氟乙烯的共聚物P（VDF-TrFE）都要快。δ相PVDF在无限电场下的切换时间快十倍，达到500皮秒。快速的切换动力学，加上低电压操作和极化的高热稳定性，使δ-PVDF成为微电子应用的合适候选材料。
