Trifluoroethylene ferroelectric

Furukawa, T., Johnson, G., Bair, H., Tajitsu, Y., Chiba, A., Fukada, E., 1981. Ferroelectric phase transition in a copolymer of vinyhdene fluoride and trifluoroethylene. Ferroelectrics 32 (1), 61-67. 

Ferroelectricity has also been found in certain copolymer compositions of VF2 with trifluoroethylene, F3E, [6-11] and tetrafluoroethylene, F4E, [12-15] and in nylon 11 [16]. Specifically, copolymers of vinylidene fluoride and trifluoroethylene (VF2/F3E) are materials of great interest because of their outstanding ferroelectricity [9,17-18], together with a parallel strong piezo- [7] and pyroelectricity [19]. These copolymers exhibit, in addition, an important aspect of ferroelectricity that so far has not been demonstrated in PVF2 the existence of a Curie temperature at which the crystals undergo reversibly a ferroelectric to a paraelectric phase transition in a wide range of compositions [9, 17-18],... 

Copolymers of VF2 with trifluoroethylene are randomly added copolymers. Those containing a mole fraction of VF2 of 50-80% have been widely studied. Since they contain a greater proportion of the comparatively bulky fluorine atoms than PVF2 their molecular chains cannot accommodate the tg+tg conformation and crystallize at room temperature in the ferroelectric phase with the extended all-trans planar conformation [37] with small statistical deviations away from that plane, i.e. copolymers of VF2 with F3E crystallize essentially with the same conformation as P-PVF2. 

Copolymers of VF2 and trifluoroethylene also exhibit a Curie temperature at which the ferroelectric crystals show reversibly a solid state transformation to... 

In the article by Balta Calleja et al., the latest results of investigations into the structure of poly(vinylidenefluoride)and its copolymers withpoly(trifluoroethylene) are summarized and extensively dicussed. These polymers are the most important ferroelectric materials. Special emphasis is placed on the relation between the change of structure and the transition from the ferroelectric into the paraelectric phase. 

Vinylidene fluoride-trifluoroethylene (VF2-F3E) copolymers exhibit a ferroelectric-paraelectric phase transition, the first such case found for a synthetic polymer. In this transition, the electric polarization and piezoelectric constant of the film disappear above the Curie point (Tcurie)- The temperature dependence of the dielectric constant, , obeys the so called Curie-Weiss law ... 

As ferroelectric material we use poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)). This copolymer is soluble in non-toxic reagents, for example 2-butanone. The preparation of organic and ferroelectric thin films via spin coating from solution is possible [13]. The polarisation field of P(VDF-TrFE) is relatively high, about 50 MV/m [14]. Here, a downscaling of the P(VDF-TrFE) film thickness into a range below 100 nm is necessary in order to use small bias voltages for polarisation. 

Several wideline NMR experiments were carried out on copolymers of vinylidene fluoride and trifluoroethylene (TrFE) [84,99-112]. Such copolymers are of special interest since TrFE in proportions greater than 10% induces the VDF component to preferentially crystallise in the )8 form. In contrast with neat PVDF, the copolymers exhibit a ferroelectric phase transition at a temperature well below melting. 

Tashiro K, Takano K, Kobayashi M, Chatani Y, Tadokoro H (1981) Structural study on ferroelectric phase transition of vinylidene fluoride-trifluoroethylene random copolymers. Polymer, 22 1312 25 195 (1984)... 

Lovinger AJ, Funikawa T, Davis GT, Broadhurst MG (1983) Crystallographic changes characterizing the Curie transition in three ferroelectric copolymers of vinylidene fluoride and trifluoroethylene. Polymer, 24 1225,1233... 

PVDF film, as produced from the melt, is largely in the nonpolar a-form, the fS phase only being obtained after subsequent processing operations, as described above. If however, vinylidene fluoride is copolymerized with as little as 7% by weight of trifluoroethylene, a copolymer is formed with crystallites completely in the / -form. This obviates the need for stretching after synthesis and the copolymer can be processed byway conventional routes, such as injection molding. Moreover, unlike PVDF, copolymers of vinylidene fluoride and trifluoroethylene have been shown to demonstrate the ferroelectric to paraelectric transition. For a copolymer with a composition of 55% vinylidene fluoride and 45% trifluoroethylene, a phase transition is observed near 70°C, and with 90% vinylidene difluoride, a phase transition at 130°C. 

For commonly used poly(vinylidene fluoride trifluoroethylene), abbreviated as P(VDF-TrFE), copolymers with a VDF content ranging from 50 to 85 mol%, the ferroelectric beta phase is stable at room temperature, and a transformation to the paraelectric alpha phase occurs above the Curie point but below the melting point [89]. Above the Curie temperature, a transition between the paraelectric and... 

Zhang QM, Bharti V, Zhao X (1998) Giant electrostriction and relaxor ferroelectric bahavior in electron-irradiated poly(vinylidene fluoride-trifluoroethylene) copolymer. Science 280 2101... 

Guo S, Zhao XZ, Zhuo Q, Chan HLW, Choy CL (2004) High electrostriction and relaxor ferroelectric behavior in proton-irradiated poly(vinylidene fluoride-trifluoroethylene) copolymer. Appl Phys Lett 84 3349... 

Xu H, Cheng ZY, Olson D, Mai T, Zhang QM, Kavamos G (2001) Ferroelectric and electromechanical properties of poly(vinylidene fluoride-trifluoroethylene-chlorotrifluoro-ethylene) terpolymer. Appl Phys Lett 78 2360... 

Bao HM, Jia CL, Wang CC, Shen QD, Yang CZ, Zhang QM (2008) A type of poly(vinylidene fluoride-trifluoroethylene) copolymer exhibiting ferroelectric relaxor behavior at high temperature (similar to 100°C). Appl Phys Lett 92 042903... 

A copolymer of vinylidene fluoride-trifluoroethylene (VDF/TrFE) copolymer is well known as the polymer for which a clear Curie point was found for the first time in an organic material. At this Curie point, the polymer undergoes a solid-to-solid phase transition from paraelectric to ferroelectric phases with decreasing temperature. Therefore, the changes in the physical properties such as crystal structure, electrical and thermal properties upon the ferroelectric phase transition have drawn many researchers interest. Here, the results concerning the ultrasomc spectroscopic mvestigation on acoustic and viscoelastic behaviour around the ferroelectric phase transition region of this copolymer are described [15]... 

Eerroelectric capacitors have been fabricated on a PEN substrate using a copolymer from vinylidene fluoride and trifluoroethylene [97]. Gold was used for the electrodes. These capacitors showed remarkable ferroelectric characteristics even when they were fabricated by a lithography-compatible patterning process at a low temperature below 150 °C. 

The copolymers of PVDF with trifluoroethylene and tet-rafluoroethylene generally crystallize into the p form [140]. Irradiation with either electron beam or y-radiation has been shown to induce soUd-state ferroelectric to paraelectric transition in these copolymers as well as a decrease in their Curie temperature [141]. 

Trifluoroethylene-c< -vinylidene fluoride Trifluoroethylene-c<>-vinylidene fluoride DSC, X-ray, and phase-contrast microscopy No phase separation by phase-contrast microscopy, a sharp single X-ray peak, intermediate in spacing between those of the individual copolymers, and clearly different from their superposition, and only one ferroelectric transition and only one melting point by DSC, indicated co-crystallization within the same lattice when I was 52/48 mol% vinylidene fluoride (VDF)/ trifluoroethylene (TFE), II was 65/35 mol% VDF/TFE, or I was 65/35 mol% VDF/TFE, and II was 73/27 mol% VDF/TFE but two X-ray peaks and two ferroelectric transitions and two melting points when I was 52/48 and II was 73/27 mol% VDF/TFE Tanaka and Lovinger (1987)... 

Piezoelectricity appears in natural crystals such as quartz, tourmaline, rochelle salt as well as in artificially produced ceramics and polymers such as e. g. nylon or copolymers of vinylidenefluoride (VDF) with trifluoroethylene (TrFE) or with tetrafluorethylene (TeFE). Most of the piezoelectric materials used for commercial sensor applications are synthetically produced polycrystalline ferroelectric ceramics such as e.g. lead-zirconate-titanate (PZT). 

Scheinbeim, J., Tang, Y. Studies on the miscibihty and ferroelectric behavior in blends of poly(vinylidene fluoride/trifluoroethylene) and poly(vinyl acetate). Journal of Polymer Science Part B Polymer Physics 41, 927-935 (2003)... 

Ohigashi, H., Omote, K. and Gomyo, T. (1995) Formation of single crystalline films of ferroelectric copolymers of vinylidene fluoride and trifluoroethylene, App. Phys Lett., 66, 3281-3. 

Recently an indication of two-dimensional ferroelectricity in ultrathin Langmuir-Blodgett (LB) films as thin as two molecular monolayers (about Inm) was discovered [1, 2] for a copolymer vinylidene fluoride with trifluoroethylene P(VDF-TrFE). The observations of the spontaneous polarization of the order of Ps 0.1 cW, the first order ferroelectric phase transition [2], a critical point [3], a surface phase transition and electric switching [1,2, 5] were reported. 

PVDF copolymers have been investigated for their piezo properties and for uses in various applications such as sensors. An example of a PVDF copolymer is polyvinylidenefluoride-co-trifluoroethylene [P(VDF-TrFE)], which is a ferroelectric, crystalline polar polymer that exhibits inherent piezoelectric and pyroelectric responses with low acoustic impedance. Such properties provide an optimistic approach towards the use of these polymers for various applications in the near future. Higashihata et al. (1981) compared the piezoelectric craistants of PVDF and P(VDF-TrFE) and observed that much larger values were obtained for P(VDF-TrFE) under the same polarizing conditions. The special interest in this copolymer is also due to the evidence reported by Furukawa et al. (1981) that the PVDF-TrFe copolymer can be annealed to 100% crystallinity, as opposed to 50% in PVDF. Other copolymers have also been explored to determine an enhanced piezo effect (Poulsen and Ducharme, 2010). 

---