Ferroelectric phase transition in a copolymer of vinylidene fluoride and trifluoroethylene

Electric Field-Induced Changes in Odd-Numbered Nylons

“…These results are similar to those typically obtained for PVF 2 and, in fact, are typical behavior for a ferroelectric material. In Figure 3(c) is shown the analagous J vs E data obtained for a film of PVF 2 , except that the low temperature range is extended down to -140'C, since the Tg for PVF 2 is --55'C.…”

“…Poled films of nylon 1I and nylon 7 were prepared and then annealed for two hours at 180°C. If such an annealing treatment had been carried out for PVF 2 …”

Investigation of ferroelectric domains in thin films of vinylidene fluoride oligomers

“…Polyvinylidene fluoride (PVDF) based ferroelectric materials have been a focus of continuous research activities [1][2][3][4][5] since the discovery of piezo-, [6][7][8] pyro-, 9,10 and ferroelectricity [11][12][13][14] in these fluorinated polymers. In particular, VDF oligomers, which contain a finite number (n) of VDF units, present a unique opportunity to not only fabricate highly ordered crystalline ultra-thin films, but also control their functional properties by varying the orientation and length of molecular chains.…”

Why ferroelectric polyvinylidene fluoride is special

“…(It turns out that an equilibrium ferroelectric phase transition temperature extrapolates to well above the material's melting point, as was determined from the effect of pressure on the transition temperature [37].) The emergence of this evidence, a decade after the discovery of piezoelectricity in PVDF [27], initiated intensive study of ferroelectric polymers [32,41]. Although the ferroelectric copolymers of VDF with TrFE and TeFE have slightly reduced spontaneous polarization, because some of the hydrogen atoms are replaced with fluorine atoms, their main advantage is that they can be annealed to nearly 100% crystallinity, whereas pure PVDF is typically limited to 50% crystallinity even with extensive annealing, stretching, and poling treatments [41].…”

“…The emergence of this evidence, a decade after the discovery of piezoelectricity in PVDF [27], initiated intensive study of ferroelectric polymers [32,41]. Although the ferroelectric copolymers of VDF with TrFE and TeFE have slightly reduced spontaneous polarization, because some of the hydrogen atoms are replaced with fluorine atoms, their main advantage is that they can be annealed to nearly 100% crystallinity, whereas pure PVDF is typically limited to 50% crystallinity even with extensive annealing, stretching, and poling treatments [41]. Increasing the disorder by, for example, electron radiation [42,43] or making a terpolymer of VDF and TrFE with 5% to 10% CTFE suppresses ferroelectricity and tends to produce polymorphous relaxors with exceptionally large electrostrictive and dielectric responses [44][45][46][47].…”