High-Electric-Field-Induced Hierarchical Structure Change of Poly(vinylidene fluoride) as Studied by the Simultaneous Time-Resolved WAXD/SAXS/FTIR Measurements and Computer Simulations

Abstract

A high electric field was applied cyclically to poly(vinylidene fluoride) films, during which the simultaneous and time-resolved measurements of the two-dimensional wideangle X-ray diffraction (WAXD), small-angle X-ray scattering (SAXS), and transmission-type Fourier transform infrared (FTIR) spectra were performed using a synchrotron X-ray radiation system. The inversion of the CF 2 dipole moments caused by the alternate change of the electric field vector direction was detected to occur around ±80−100 MV/m as estimated by the electricfield-strength dependence of the IR band intensity. On the other hand, the WAXD peaks were found to show the maximal intensities at 0 and ±250−300 MV/m. In these regions, the 001 reflection of the β form and the 002 reflection of the δ form changed the intensities remarkably and periodically. These experimental data were interpreted, not by the idea of a simple inversion motion of the rigid polar chains (the planar zigzag chains of the form β and the TGTG̅ chains of the α and δ forms) but by the more complicated couplings between the rotation and tilting motions of the chain segments, the cooperative T-G conformational exchanges, and the associated inversion motion of the CF 2 dipoles. The idea of the cooperative chain motions was supported by the density functional theory calculations performed under the external electric field. Different from the remarkable changes of the WAXD and FTIR data, the SAXS patterns did not show the detectable changes in these processes, indicating that the above-mentioned cooperative structural changes should occur in the crystalline regions with the stacked lamellar structure kept unchanged.

$δ$-PVDF Based Flexible Nanogenerator

“…Thus, as a result 1209 cm −1 absorption band does not appear in IR spectra of δ -phase. 36 This observation is consistent with FTIR spectra of PVDF nanoparticles processed via electrospray. Additionally, the FTIR spectra (Fig.…”

“…The fourier transform infrared spectroscopy (FTIR) study of the nanoparticles (Fig. S3 (marked as δ ), supplementary material) shows the IR absorption bands of δ -PVDF as reported by K. Tashiro et al 36 . The vibrational bands at 1182 cm −1 and 1209 cm −1 are one of the conclusive way to identify the δ -phase through FTIR.…”

An Optical/Ferroelectric Multiplexing Multidimensional Nonvolatile Memory from Ferroelectric Polymer

“…[ 7 ] Large‐scale transformation from α‐phase to β‐phase is induced by thermal and UV‐annealing, [ 8 ] mechanical deformation, [ 9 ] and electric field poling. [ 10 ] Very recently, Ding et al. demonstrated that nanoannealing of PVDF films could also be induced by gold nanoparticle‐assisted plasmonic heating under irradiation of continuous waver laser, which substantially facilitates the α‐ to β‐phase transformation.…”

“…[7] Large-scale transformation from α-phase to β-phase is induced by thermal and UV-annealing, [8] mechanical deformation, [9] and electric field poling. [10] Very recently, Ding et al demonstrated that nanoannealing of PVDF films could also be induced by gold nanoparticle-assisted plasmonic heating under irradiation of continuous waver laser, which substantially facilitates the αto β-phase transformation. [11] With different conformations (trans-gauche-trans-gauche′ [TGTG′] for α-phase and all-trans [TTTT] for β-phase), Multiplexing physical dimensions to realize multidimensional storage in a single material has been a goal to increase storage density and data security.…”

Electric-Field-Induced Phase Transition and Crystal Structural Change of the Oriented Poly(vinylidene Fluoride) β Form as Clarified by the In Situ Synchrotron Wide-Angle X-ray Diffraction Measurement

“…In order to trace the structural change of PVDF films in the electric field from the wide hierarchical structure levels, the present authors challenged to simultaneously measure two-dimensional WAXD patterns, the small-angle X-ray scattering (SAXS) patterns, and the transmission-type IR spectra in the process of stepwise change of electric field strength in the range of 0 to ±400 MV/m by using the synchrotron X-ray radiation system combined with a miniature FTIR spectrometer . The samples used there were the commercially available biaxially oriented PVDF films composed of the crystal forms α and β.…”