Over the last half century, the existence of an additional thermal transition in between the glass transition and the Curie/melting transition has been frequently observed on vinylidenefluoride-based ferro-, pyro- and piezoelectric homo- and co-polymers. The transition has also been observed recently in some of the related relaxor-ferroelectric terpolymers. Despite its well-known existence and the rich history of its treatment in the literature, the origin(s) and a more or less complete picture of the mid-temperature transition have remained elusive until now. Over the years, several authors have put forth various explanations for the so-called mid-temperature transition — some complementary and some contradictory to each other. At the 17th IEEE International Symposium on Electrets (ISE-17) in Limerick, Ireland, in September 2019, the mysterious mid-temperature transition and its possible mechanism(s) became the subject of a panel discussion a) to mark the Golden Jubilee of the discovery of piezoelectricity in polyvinylidenefluoride (PVDF) by Heiji Kawai of Kobayashi Institute of Physical Research, Japan, as well as the Centennial of the first recognition of ferroelectricity in piezoelectric Seignette's or Rochelle salt. The panel put forward a new hypothesis that the mid-temperature transition is most likely a result of several interrelated processes that take place within the respective temperature range. The relevant processes include an upper glass transition or relaxation, a relaxation related to conformational disorder, possible imperfect/time-dependent structures formed as a result of thermal processing and secondary crystallization, as well as interface polarization effects at crystalline-amorphous boundaries. The article captures the essence of the panel discussion and the perspectives obtained therefrom to elucidate the complex mid-temperature transition in vinylidenefluoride-based ferro-, pyro- and piezoelectric homo-, co- and ter-polymers.

中文翻译：

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基于偏二氟乙烯的均聚物、共聚物和三元共聚物中温转变背后的奥秘——难题是否已解决？

在过去的半个世纪里，在基于偏二氟乙烯的铁、热和压电均聚物和共聚物上经常观察到玻璃化转变和居里/熔融转变之间存在额外的热转变。最近在一些相关的弛豫-铁电三元共聚物中也观察到了这种转变。尽管它的存在众所周知，并且在文献中有着丰富的处理历史，但直到现在，中温转变的起源和或多或少的完整图景仍然难以捉摸。多年来，几位作者对所谓的中温转变提出了各种解释——有些是互补的，有些是相互矛盾的。在 2019 年 9 月在爱尔兰利默里克举行的第 17 届 IEEE 驻极体国际研讨会 (ISE-17) 上，神秘的中温转变及其可能的机制成为小组讨论的主题 a) 纪念日本小林物理研究所的 Heiji Kawai 发现聚偏二氟乙烯 (PVDF) 中的压电性的金禧，作为以及首次确认压电 Seignette 盐或 Rochelle 盐中的铁电性百年纪念。该小组提出了一个新假设，即中间温度转变很可能是在相应温度范围内发生的几个相互关联的过程的结果。相关过程包括上部玻璃化转变或弛豫、与构象无序相关的弛豫、由于热处理和二次结晶而形成的可能的不完美/时间依赖性结构，以及晶体 - 非晶边界处的界面极化效应。这篇文章抓住了小组讨论的本质以及从中获得的观点，以阐明基于偏二氟乙烯的铁基、热基和压电均聚物、共聚物和三元共聚物中复杂的中温转变。