Vinylidene fluoride ferroelectric

Lovinger AJ, Furukawa T (1983) Curie transitions in copolymers of vinylidene fluoride. Ferroelectrics 50 227... 

Baltd-Calleja, F. J., Gonzalez Arche, A., Ezquerra, T. A., Santa Cruz, C., Batallon, F., Frick, B. and Lopez Cabarcos, E. Structure and Properties of Ferroelectric Copolymers of Poly(vinylidene) Fluoride. Vol. 108, pp. 1-48. 

Note 2 Poly(vinylidene fluoride) after being subjected to a corona discharge is an example of a ferroelectric polymer. 

Barium titanate is one example of a ferroelectric material. Other oxides with the perovskite structure are also ferroelectric (e.g., lead titanate and lithium niobate). One important set of such compounds, used in many transducer applications, is the mixed oxides PZT (PbZri-Ji/Ds). These, like barium titanate, have small ions in Oe cages which are easily displaced. Other ferroelectric solids include hydrogen-bonded solids, such as KH2PO4 and Rochelle salt (NaKC4H406.4H20), salts with anions which possess dipole moments, such as NaNOz, and copolymers of poly vinylidene fluoride. It has even been proposed that ferroelectric mechanisms are involved in some biological processes such as brain memory and voltagedependent ion channels concerned with impulse conduction in nerve and muscle cells. 

Photovoltaic volume effects have been investigated for the ferroelectric polymer-poly vinylidene fluoride [84,85]. The photovoltage was of the order 4 x 104 V for open circuit. The addition of dyes shifts the photosensitivity to the longer wavelength. 

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],... 

Structure and Properties of Ferroelectric Copolymers of Poly(Vinylidene Fluoride)... 

Materials. For holographic information storage, materials are required which alter their index of refraction locally by spotwise illumination with light. Suitable are photorefractive inorganic crystals, eg, LiNb03, BaTi03, LiTa03, and Bi SiO. Also suitable are photorefractive ferroelectric polymers like poly(vinylidene fluoride-co- trifluorethylene) (PVDF/TFE). Preferably transparent polymers are used which contain approximately 10% of monomeric material (so-called photopolymers, photothermoplasts). These polymers additionally contain different initiators, photoinitiators, and photosensitizers. 

Poly(vinylidene fluoride) with the sequence (CF2-CH2)n is a well known ferroelectric polymer in the crystalline state where the chains adopt an all-trans conformation [424]. This structure could provide interesting properties if used as building block of LC. 

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