Influence of Steric Hindrance on Ferro‐ and Piezoelectric Performance of Poly(vinylidene fluoride)‐Based Ferroelectric Polymers

Abstract

Poly(vinylidene fluoride) (PVDF) and copolymers possess excellent ferro‐ and piezoelectric properties, and highly expected to be utilized as sensors in the areas covering the smart wearer, hydrophone, speaker, and medical ultrasonic devices. Besides PVDF in β crystalline phase, the copolymers with trifluoroethylene (TrFE) and tetrafluoroethylene (TFE) are widely investigated both in academia and industry. To illustrate how the steric hindrance between VDF and TrFE/TFE affects the condensed‐state structure and electric properties of the polymers, the electric properties and their dependences on molecular configuration and crystal structures of PVDF, P(VDF‐TrFE), and P(VDF‐TFE) are comparatively investigated. The introduction of same molar contents (20 mol%) of TrFE and TFE monomers into PVDF chain leads to the similar conformation transformation from α (γ ) phase to β phase and similar crystallinity in resultant P(VDF‐TFE) and P(VDF‐TrFE) thanks to the depressed energy of trans conformation and the increased energy barrier between anti‐gauche and trans conformation. That leads to the more preferred β‐phase and ferroelectric domains generated in P(VDF‐TrFE) and P(VDF‐TFE). Both the size of ferroelectric phase, the polarity of the polymer chain, the organization and orientation of the grains along the field are responsible for the excellent piezoelectric field resulted by the varied composition as well.

Composition Dependence of Microstructures and Ferroelectric Properties in Poly(vinylidene fluoride-ter-trifluoroethylene-ter-chlorodifluoroethylene) Terpolymers

“…The nonpolar α phase, despite being the most accessible one, is paraelectric because of the TGTG′ (T: trans ; G: gauche ) conformation and antiparallel chain packing. By copolymerizing VDF with trifluoroethylene (TrFE), the resulting P­(VDF-TrFE) copolymers can directly crystallize into the ferroelectric β phase from the melt or solution. − Another example of the copolymer showing a similar ferroelectric phase is P­(VDF-TFE) (TFE: tetrafluoroethylene) …”

“…11−14 Another example of the copolymer showing a similar ferroelectric phase is P(VDF-TFE) (TFE: tetrafluoroethylene). 15 P(VDF-TrFE) (TrFE: trifluoroethylene) has long been considered as normal ferroelectric materials with large polarization hysteresis and has a maximized piezoelectric coefficient d 33 of ca. −30 pC/N.…”

Facile fabrication of ferroelectric poly(vinylidene fluoride) thin films with pure γ phase

“…17–20 Therefore, strategies including regulation of the chemical structure, incorporation of additives, and altering the fabrication conditions or environment have been investigated. 21–30…”

“…[17][18][19][20] Therefore, strategies including regulation of the chemical structure, incorporation of additives, and altering the fabrication conditions or environment have been investigated. [21][22][23][24][25][26][27][28][29][30] Incorporating trifluoroethylene (TrFE) into the PVDF chains, namely PVDF-TrFE copolymer, is effective for the direct generation of the polar b-like ferroelectric phase. 20 It exhibits, however, a low Curie temperature.…”

Factors affecting the piezoelectric performance of ceramic-polymer composites: A comprehensive review

“…Materials exhibiting piezoelectric properties are classified into three main categories, ceramics, polymers, and composites [9]. These materials can either exist naturally (such as quartz, cane sugar, collagen, topaz, and Rochelle salt) [6,10,11] or can be synthesised chemically such as perovskites [10,12], synthetic polymers [13][14][15] or piezoelectric composites [16,17]. These materials have characteristic individual advantages that can be beneficial towards specific applications.…”