Synthesis and Properties of Ferroelectric Fluoroterpolymers with Curie Transition at Ambient Temperature

Abstract

This paper discusses a new family of ferroelectric polymorphic fluoroterpolymers comprosed of vinylidene difluoride (VDF), trifluoroethylene (TrFE), and a chloro-containing third monomer, such as chlorodifluoroethylene (CDFE), and chlorotrifluoroethylene (CTFE), which feature relatively narrow molecular weight and composition distributions. The terpolymers were prepared by a bulk reaction process with a low temperature free radical initiator, i.e., the oxidation adducts of trialkylborane and oxygen. The slightly bulky chlorine atom serves as a kink in the polymer chain, which spontaneously alters the chain conformation and crystalline structure. Compared to the corresponding VDF/TrFE copolymer (>20 mol % of TrFE), the slowly increasing chlorine content (<8 mol % of termonomer) gradually changes the all-trans (t m >4) chain conformation (β-phase) to tttg+tttg- conformation (γ-phase) without significant reduction of overall crystallinity. The Curie (ferroelectric−paraelectric) phase transition temperature between the mixed ferroelectric β- and γ-phases and paraelectric α-phase (tg+tg- conformation) also gradually reduced to near ambient temperature with very small activation energy. Consequently, the terpolymers show high dielectric constant (>70), slim polarization hysteresis, and large electrostrictive response (>4%) at ambient temperature and exhibit common ferroelectric relaxor behaviors with a broad dielectric peak that shifted toward higher temperatures as the frequency increased.

Effect of crystallinity on surface morphology and light transmittance of poly(vinylidene fluoride‐co‐hexafluoropropylene) thin film

“…As shown in Figure 1, 19 F-NMR spectrum of P(VDFco-HFP) exhibits three major regions originated from CF 3 (À68 to À80 ppm), CF 2 (À90 to À130 ppm), and CF group (À180 to À190 ppm), respectively. 18 The monomer composition in copolymers could be calculated from the areas of CF 3 and CF 2 groups in 19 F-NMR spectrum. 19 F-NMR spectrum provides information not only on monomer composition but also on copolymer chain sequence.…”

“…Chemical composition and monomer sequence of synthesized polymers were determined by 19 Fluorine nuclear magnetic resonance spectroscopy ( 19 F-NMR, Bruker DRX-300, Am Silberstreifen, Germany). Sample was dissolved in acetone-d 6 with a concentration of 8 wt %.…”

“…The chemical composition of copolymers was controlled by the monomer feed concentration (20-30 mol % HFP) and determined by 19 F-NMR analysis. As shown in Figure 1, 19 F-NMR spectrum of P(VDFco-HFP) exhibits three major regions originated from CF 3 (À68 to À80 ppm), CF 2 (À90 to À130 ppm), and CF group (À180 to À190 ppm), respectively.…”

“…18 The monomer composition in copolymers could be calculated from the areas of CF 3 and CF 2 groups in 19 F-NMR spectrum. 19 F-NMR spectrum provides information not only on monomer composition but also on copolymer chain sequence. In comparison with PVDF [ Fig.…”

Synthesis and microstructure of a novel graft copolymer from poly(vinylidene fluoride–chlorotrifluoroethylene–trifluoroethylene)

“…Among these crystalline phases, the polar β-phase is the most interesting and important one because it exhibits a strong ferroelectric behavior. [10][11][12] In order to obtain high performance and inexpensive electroactive polymers (EAPs), many efforts have been made to modify the crystal structure and morphology in the PVDF-based polymers, including studies of the effects of irradiation on PVDF-based copolymer [13][14][15][16] and terpolymers, [17][18][19][20] PVDF-based composites, [4,[21][22][23] and PVDFbased polymer blends with thermal treatment. [24][25][26] However, as an important method of modifying polymers, graft copolymerization of comonomers from the backbone of these ferroelectric fluoropolymers was seldom adopted to prepare high performance EAPs.…”