Ferroelectric polymers

Abstract

In the early 1970s it became clear that the polymer polyvinylidene fluoride is ferroelectric. There have been extensive studies of its properties and of the properties of copolymers of vinylidene fluoride with tri-or tetra-fluoroethylene. This work has led to a fairly complete understanding of the ferroelectric and related properties of these materials. The emphasis in this review is on the studies of these materials that are oriented toward showing that the polymers are indeed ferroelectric, determining the mechanism of polarization reversal, and understanding the origins of the observed piezoelectric and pyroelectric effects. Very recently some odd nylons (nylons with an odd number of carbon atoms in the monomer unit) were recognized to be ferroeleetrie, and ferroelectric liquid-crystalline polymers have been prepared by attaching ferroelectric liquid-crystal molecules as side chains to polymer backbones. These new findings are included in the review. Contents

Change in dielectric relaxation with the presence of water in highly filled composites

“…4 and 6, which could be regarded as the desorption event; susceptibility should increase with temperature due to the nature of the material, there are no ferroelectric transitions to cause decrease in the real part of the susceptibility. [20][21][22]25 The number of relaxations that can be observed in wet sample is larger than the dried sample. As discussed previously, at high temperatures close to 300 C, the data for the wet and dried sample are converging to each other indicating the similarities in both responses and confirm that the initial measurement in the first ramp is a dry-bake cycle.…”

Electromagnetic Shielding Features in Lightweight PVDF-Aluminum Based Nanocomposites

“…Extensive literature exists on the conditions under which specific phases are obtained; a discussion without ending, because the crystal phases are close in terms of stability and thus small changes in processing conditions may cause another phase to appear. At present, it is understood that at room temperature, it is the α-phase that forms most readily and close to the melting point it is the γ-phase [24][25][26]. The β-phase, which has the largest ferroelectric moment, appears to be the stable phase at higher pressures [27,28], and once obtained it does not normally convert into other phases under ambient conditions.…”

“…The β-phase, which has the largest ferroelectric moment, appears to be the stable phase at higher pressures [27,28], and once obtained it does not normally convert into other phases under ambient conditions. There is an abundance of literature describing the interconversion of one phase into another [24][25][26].…”

Recent Development in Polymer Ferroelectric Field Effect Transistor Memory

“…Piezoelectric transducers made by solvent casting were soon commercially available, though it took a decade to establish that ferroelectricity was the origin of these effects in PVDF. Synthesis of PVDF and its copolymers has been standardized and is thoroughly described in the texts edited by Wang et al [27] and Nalwa [28], and in several review articles [29][30][31]. PVDF is the most widely used ferroelectric polymer and is manufactured in large quantities for a wide variety of applications, ranging from protective coatings to ultrasound transducers.…”