Polyvinylidene fluoride (PVDF) and its copolymers, since the discovery of their piezoelectric and pyroelectric properties, have attracted research interest due to their application in the fields of sensors, actuators, medical imaging, IR detectors, underwater acoustic transducers and emerging organic electronics. The piezoelectric, pyroelectric, and ferroelectric properties of VDF-based resins as well as their transition behavior were extensively studied during the 70s and 80s. However, the application of the PVDF homopolymer was limited because it does not crystallize directly into its ferroelectric ?-phase. In order to obtain a ferroelectric material, PVDF thick films have to be mechanically stretched and then poled under a high electric field. On the other hand, PVDF copolymers, such as poly(vinylidene fluoride/trifluoroethylene) P(VDF-TrFE), directly form a ferroelectric phase from solution or melt. The copolymer has been observed to exhibit a crystal-to-crystal transition below the melting point called a Curie transition where a dipole ordered ferroelectric phase converts to a dipole disordered paraelectric phase upon heating. In 1997, we presented the possibility of the Curie transition going from an ordered phase to a conformational disordered phase (I. George & L. Judovits, Thermochimica ACTA, 302 (1997) 77-85). Recent work by F. Bargain, P. Panine, F. Domingues Dos Santos, and S. Tence-Girault (Polymer 105 (2016) 144-156) appears to support the hypothesis that the high temperature phase that forms is conformationally disordered.
展开▼
机译：聚偏二氟乙烯（PVDF）及其共聚物，由于其压电和热电性质的发现，由于其在传感器，致动器，医学成像，红外探测器，水下声换能器和新兴的有机电子领域的应用而吸引了研究兴趣。在70年代和80年代，对VDF基树脂的压电，热电和铁电特性及其过渡行为进行了广泛的研究。但是，PVDF均聚物的应用受到限制，因为它不会直接结晶成铁电α相。为了获得铁电材料，必须将PVDF厚膜进行机械拉伸，然后在高电场下极化。另一方面，PVDF共聚物（例如聚偏二氟乙烯/三氟乙烯）P（VDF-TrFE）可直接从溶液或熔体形成铁电相。已经观察到该共聚物在低于居里转变的熔点下显示出晶体-晶体转变，其中在加热时偶极有序的铁电相转变为偶极无序顺电相。在1997年，我们提出了居里跃迁从有序相转变为构象无序相的可能性（I. George＆L. Judovits，Thermochimica ACTA，302（1997）77-85）。 F.Bargain，P.Panine，F.Domingues Dos Santos和S.Tence-Girault（Polymer 105（2016）144-156）的最新工作似乎支持以下假设：形成的高温相在构象上无序。
展开▼
