ABSTRACT
Ferroelectric properties of organic polymers have been investigated since the 19608, when piezoelectricity· was first discovered, in polypeptides, poly(methyl methacrylate) (PMMA), poly(vinyl chloride) (PVC), and poly(vinylidene fluoride) (pVDF). Ferroelectric polymers began to attract much attention when a significant enhancement of piezoelectricity was observed for PVDF by electret formation. Over the years, a number of applications of PVDF were investigated that include audiofrequency transducers, ultrasonic transducers, electromechanical transducers, pyroelectric detectors, robotics, and biosensors [1]. To date, PVDF has been the most successful material because of its wide range of applications in electronics and biomedical engineering. With the discovery of PVDF, the field was confronted with challenges to develop novel organic polymers with large pyroelectric, piezoelectric, and ferroelectric responses. With this quest, new ferroelectric polymeric systems have been sought for potential use in a variety of electronic and photonic devices. Virtually together, co-polymerization of VDF with trifluoroethylene and tetrafiuoroethylene were found to be useful, since co-polymers crystallize spontaneously into a ferroelectric phase and exhibit a high degree of crystallinity as well as large piezoelectric response. The most promising polymers found so far include PVDF and its co-polymers, co-polymers of poly(vinylidene cyanide), odd-numbered nylons, polyureas, and polymer composites of piezoelectric ceramics [2,3]. Odd-numbered nylons have emerged as a new class of ferroelectric polymers similar to PVDF. The dielectric, pyroelectric, piezoelectric, and ferroelectric properties of various odd-numbered nylons are discussed in this chapter.
