186:
molecules contain two hydrogen and two fluorine atoms per repeat unit, so they have a choice of multiple conformations. However, rotational barriers are relatively high, the chains can be stabilized into favorable conformations other than that of lowest energy. The three known conformations of PVDF are all-trans, tgtg, and tttgtttg. The first two conformations are the most common ones and are sketched out in the figure on right. In the tgtg conformation, the inclination of dipoles to the chain axis leads to the polar components of both perpendicular (4.0 Ă 10 C-m per repeat) and parallel to the chain (3.4 Ă 10 C-m per repeat). In the all trans structure, the alignment of all its dipoles are in the same direction normal to the chain axis. In this way, it can be expected that the all trans is the most highly polar conformation in PVDF (7.Ă 10 C-m per repeat). These polar conformations are the crucial factors that lead to the ferroelectric properties.
217:. This can be disadvantageous because lead can be potentially harmful and at high particulate loading, the polymers lose their flexibility and a low quality composite is obtained. Current advances use a blending procedure to make composites that are based on the simple combination of PVDF and cheap metal powders. Specifically, Ni powders were used to make up the composites. The dielectric constants were enhanced from values there were less than 10 to approximately 400. This large enhancement is explained by the
105:
Ferroelectric polymers differ in that the entire body undergoes polarization, and the requirement of heat is not necessary. Although they differ from electrets, they are referred to as electrets often. Ferroelectric polymers fall into a category of ferroelectric materials known as an 'order-disorder' material. This material undergoes a change from randomly oriented dipoles which are paraelectric, to ordered dipoles which become ferroelectric.
125:
141:
polyvinylidene fluoride. Two years later, the ferroelectric properties of the same polymer were reported. Throughout the 1970s and 1980s, these polymers were applied to data storage and retrieval. Subsequently, there has been tremendous growth during the past decade in exploring the materials science, physics, and technology of poly(vinylidenefluoride) and other fluorinated polymers.
229:
101:
stretching and compressing the polymer, measure generated electric fields. Pyroelectric behavior stems from the change in temperature causing electric behavior of the material. While only ferroelectric behavior is required for a ferroelectric polymer, current ferroelectric polymers exhibit pyroelectric and piezoelectric behavior.
316:. The flexibility and low cost of polymers facilitates the application of ferroelectric polymers in transducers. The device configuration is simple, it usually consists of a piece of ferroelectric film with an electrode on the top and bottom surfaces. Contacts to the two electrodes complete the design.
224:
These ferroelectric materials have also been used as sensors. More specifically, these types of polymers have been used for high pressure and shock compression sensors. It has been discovered that ferroelectric polymers exhibit piezoluminescence upon the application of stress. Piezoluminescence has
104:
In order to have an electric polarization that can be reversed, ferroelectric polymers are often crystalline, much like other ferroelectric materials. Ferroelectric properties are derived from electrets, which are defined as a dielectric body that polarizes when an electric field and heat is applied.
100:
A consequence of ferroelectric behavior leads to piezoelectric behavior, where the polymer will generate an electric field when stress is applied, or change shape upon application of an electric field. This is viewed as shrinking, or changes in conformation of the polymer in an electric field; or by
287:
technology to produce nonvolatile ferroelectric random-access memory and data-storage devices. Recent research with LB films and more conventional solvent formed films shows that the VDF copolymers (consisting of 70% vinylidene fluoride (VDF) and 30% trifluoroethylene (TrFE)) are promising materials
253:
liquid crystal displays. In the same time period, the first side-chain liquid crystalline polymers (SCLCP) were synthesized. These comb-like polymers has mesogenic side chains that are covalently bonded (via flexible spacer units) to the polymer backbone. The most important feature of the SCLCP's
80:
A ferroelectric polymer must contain permanent electrical polarization that can be reversed repeatedly, by an opposing electric field. In the polymer, dipoles can be randomly oriented, but application of an electric field will align the dipoles, leading to ferroelectric behavior. In order for this
185:
interactions, the rotation about single bonds happens in the chain of PVDF. There are two most favorable torsional bond arrangements: trans ( t ) and gauche ( g ). In the case of â tâ, the substituents are at 180° to each other. In the case of âgâ, the substituents are at ±60° to each other. PVDF
249:(SSFLC) structure. This opened up promising possibility of technical applications of ferroelectric liquid crystals in high-information display devices. Through applied research, it was shown that SSFLC structure has faster switching times and bistability behavior in comparison with commonly used
236:
It is useful to distinguish among the several regimes in a typical stressâstrain curve for a solid material. The three regimes of the stressâstrain curve include elastic, plastic, and fracture. Light emitted in the elastic regime is known piezoluminescence. Fig. 7 shows a general stressâstrain
194:
Ferroelectric polymers and other materials have been incorporated into many applications, but there is still cutting edge research that is currently being done. For example, there is research being conducted on novel ferroelectric polymer composites with high dielectric constants. Ferroelectric
240:
These types of polymers have played a role in biomedical and robotic applications and liquid crystalline polymers. In 1974, R.B. Meyer predicted ferroelectricity in chiral smectic liquid crystals by pure symmetry conditions. Shortly after, Clark and
Lagerwall had done work on the fast
140:
structure, but ferroelectrics can also be grouped into three other categories. These categories include organic polymers, ceramic polymer composites, and compounds containing hydrogen-bonded radicals. It wasn't until 1969 that Kawai first observed the piezoelectric effect in a polymer
108:
After the discovery of PVDF, many other polymers have been sought after that contain ferroelectric, piezoelectric, and pyroelectric properties. Initially different blends and copolymers of PVDF were discovered, such as a polyvinylidene fluoride with
578:
Tashiro, K.; Takano, K.; Kobayashi, M.; Chatani, Y.; Tadokoro, H. (2011). "Structural study on ferroelectric phase transition of vinylidene fluoride-trifluoroethylene copolymers (III) dependence of transitional behavior on VDF molar content".
288:
for nonvolatile memory applications. The device is built in the form of the metalâferroelectricâinsulatorâsemiconductor (MFIS) capacitance memory. The results demonstrated that LB films can provide devices with low-voltage operation.
145:
PVDF with trifluoroethylene and odd-numbered nylons were additional polymers that were discovered to be ferroelectric. This propelled a number of developing applications on piezoelectricity and pyroelectricity.
515:
132:
The concept of ferroelectricity was first discovered in 1921. This phenomenon began to play a much larger role in electronic applications during the 1950s after the increased use of BaTiO
232:
Figure 7: Stressâstrain curve showing the different regions. Light seen at fracture is known as triboluminescence and light emitted in the elastic regime is known as piezoluminescence.
195:
polymers, such as polyvinylidene fluoride and poly, are very attractive for many applications because they exhibit good piezoelectric and pyroelectric responses and low
332:
force applied to one of the surfaces causes a compression of the material. Via the direct piezoelectric effect, a voltage is generated between the electrodes.
77:
First reported in 1971, ferroelectric polymers are polymer chains that must exhibit ferroelectric behavior, hence piezoelectric and pyroelectric behavior.
825:
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199:, which matches water and human skin. More importantly, they can be tailored to meet various requirements. A common approach for enhancing the
65:
93:
861:
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Bauer, Siegfried; Gerhard-Multhaupt, Reimund; Sessler, Gerhard M. (2004). "Ferroelectrets: Soft
Electroactive Foams for Transducers".
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is to disperse a high-dielectric-constant ceramic powder into the polymers. Popular ceramic powders are lead-based complexes such as
262:
and optical data storage devices. The disadvantage is that these SCLCP's suffered from their slow switching times due to their high
562:
428:
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128:
Figure 3: Brief timeline describing important events that have occurred in piezoelectricity and ferroelectric polymer history
254:
is their glassy state. In other words, these polymers have a "frozen" ordered state along one axis when cooled below their
116:
Other structures were discovered to possess ferroelectric properties, such as polytrifluoroethylene and odd-numbered nylon.
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283:
loop, which is related to "memory". One application is integrating ferroelectric polymer
LangmuirâBlodgett (LB) films with
255:
344:, a voltage applied between the electrodes causes a strain on the film through the inverse piezoelectric effect.
291:
110:
557:. Overton, Rourke, Weller, Armstrong (Fourth ed.). New York: W.H. Freeman and Company. pp. 609â610.
752:
688:
Dang, Zhi-Ming; Ce-Wen Nan (2003). "Novel
Ferroelectric Polymer Composites with High Dielectric Constants".
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The ferroelectric effect always relates the various force to electric properties, which can be applied in
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behavior, which does not allow for ferroelectric behavior because the electric fields do not align.
874:
Kressmann, R. (2001). "New piezoelectric polymer for air-borne and water-borne sound transducers".
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298:
200:
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Bauer, Francois (2002). "Ferroelectric
Polymers for High Pressure and Shock Compression Sensors".
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Reynolds, George (1997). "Piezoluminescence from a ferroelectric polymer and quartz".
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in the form of ferroelectric polymer foams have been proved to have great potential.
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789:"Ferroelectric polymer Langmuir-Blodgett films for nonvolatile memory applications"
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394:"Ferroelectric Properties of Vinylidene Fluoride Copolymers," by T. Furukawa, in
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Development Manufacturing Award
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To minimize the potential energy of the chains arising from internal
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Polyvinylidine fluoride is produced by the radical polymerization of
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614:
Nalwa, H.S. (1991). "Recent development in ferroelectric polymers".
136:. This ferroelectric material is part of the corner-sharing oxygen
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PolyIC, ThinFilm announce pilot of volume printed plastic memories
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123:
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The ferroelectric property exhibits polarizationâelectric-field-
16:
Group of crystalline polar polymers that are also ferroelectric
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Ducharme, D.; Reece, T.J.; Othon, C.M.; Rannow, R.K. (2005).
862:
Thin Film
Electronics Plans to Provide âMemory Everywhereâ
516:
IEEE Transactions on
Dielectrics and Electrical Insulation
57:
response, and as heat sensors because of their inherent
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All set for high-volume production of printed memories
696:(19). Tsinghua University: Communications: 1625â1628.
511:"Why Ferroelectric Polyvinylidene Fluoride is Special"
793:
IEEE Transactions on Device and
Materials Reliability
225:
been looked for in materials that are piezoelectric.
258:. This is advantageous for research in the area of
85:. Above the Curie Temperature, the polymer exhibits
34:that can be reversed, or switched, in an external
453:Lovinger, A.J. (1983). "Ferroelectric polymers".
81:effect to happen, the material must be below its
423:(First ed.). New York: Marcel Dekker, INC.
68:Figure 1: Structure of poly(vinylidene fluoride)
245:effect in a surface-stabilized ferroelectric
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96:Figure 2: Structure of polytrifluoroethylene
616:J. Macromol. Sci. Rev. Macromol. Chem. Phys
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641:Kepler, R.G.; Anderson, R.A. (1992).
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509:Poulsen, M.; Ducharme, S.. (2010).
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864:Printed Electronics Now, May 2010
22:are a group of crystalline polar
41:Ferroelectric polymers, such as
324:When the device functions as a
1:
774:10.1016/S0022-2313(97)00134-8
739:. Materials Research Society.
475:10.1126/science.220.4602.1115
45:(PVDF), are used in acoustic
256:glass transition temperature
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840:EETimes, 22 September 2009
294:successfully demonstrated
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53:because of their inherent
760:(4). Princeton: 295â299.
667:10.1080/00018739200101463
628:10.1080/15321799108021957
593:10.1080/00150198408012770
553:Atkins, P. (2006). "23".
529:10.1109/TDEI.2010.5539671
111:poly(methyl methacrylate)
805:10.1109/TDMR.2005.860818
733:Mat. Res. Soc. Symposium
643:"Ferroelectric polymers"
967:Ferroelectric materials
828:IDTechEx, 15 April 2009
753:Journal of Luminescence
361:Polyvinylidene fluoride
156:Polyvinylidene fluoride
150:Polyvinylidene fluoride
43:polyvinylidene fluoride
710:10.1002/adma.200304911
421:Ferroelectric Polymers
233:
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49:and electromechanical
20:Ferroelectric polymers
402:, pp. 143â211 (1989).
302:non-volatile memories
292:Thin Film Electronics
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32:electric polarization
264:rotational viscosity
931:2004PhT....57b..37B
888:2001ASAJ..109.1412K
766:1997JLum...75..295R
702:2003AdM....15.1625D
659:1992AdPhy..41....1K
647:Advances in Physics
555:Inorganic Chemistry
467:1983Sci...220.1115L
461:(4602): 1115â1121.
201:dielectric constant
167:vinylidine fluoride
876:J. Acoust. Soc. Am
690:Advanced Materials
419:Nalwa, H. (1995).
328:, a mechanical or
275:Nonvolatile memory
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219:percolation theory
197:acoustic impedance
173:Study of Structure
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961:Categories
622:(4): 341.
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212:Pb(Zr,Ti)O
138:octahedral
73:Background
61:response.
947:0031-9228
675:0001-8732
601:0015-0193
342:actuators
336:Actuators
161:Synthesis
143:Copolymer
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972:Polymers
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355:See also
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24:polymers
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320:Sensors
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