STUDY ON PHASE TRANSITION AND CRITICAL PHENOMENA IN POLYMER CRYSTALS BASED ON LIGHT-HEATING MODULATED DTA AND HIGH PRESSURE MEASUREMENT

严格证明聚合物晶体中存在二级相变的报道在国际上尚未见报道。我们最近在高压下的X射线结构分析的基础上发现了聚酰胺晶体的二级相变。通过这些研究，我们注意到世界上还没有对高压下的比热测量进行定量分析，这为我们讨论材料中的相变现象提供了最重要的信息之一。本项目的第一步是构建光热调制温度差热分析高压系统(HP-LMTDTA)，用于聚合物的动态热测量。构建后，我们利用1，4-反式聚丁二烯晶体的相变现象来测试系统的性能，证明了测量相变…过程中动态过程的热性质是可能的通过这个项目，我们主要分析了尼龙和含氟共聚物晶体中的相变现象，发现即使在常压和高压下，尼龙6Y(Y：偶数≦8)晶体也只发生一级和/或二级相变。随着偏氟乙烯(VDF)摩尔分数的增加或外加压力的增加，偏氟乙烯(VDF)-三氟乙烯(TrFE)共聚物晶体的结构发生了从连续相(冷却相)到高温相(HP)到不连续相(低温相)的转变，其中CP到LP的转变发生在从LP到HP的一级相变之前。VDF含量为65%的样品仅由CP组成，其中68%的样品突然出现Lp，VDF71和77%的样品可能存在另一种Lp。渗流理论可以用来解释这种对VDF含量非常敏感的结构转变。这一结果表明，该体系可以从分子水平上应用于聚合物的高压下的各种研究，如晶体生长和熔融、球晶形成过程、电学性能等。

There had been no reports in the world, which strictly proved appearance of second-order phase transition in polymer crystals. We recently discovered the second-order phase transition in polyamide crystals on the basis of X-ray structure analysis under high-pressure. Through such studies, we noticed that the quantitative analysis had not been performed for specific-heat measurement under high-pressure in the world, which must give us one of the most important information to discuss the phase-transitional phenomena in material. It is the reason why we started this project.The first step of this project is to construct the high-pressure system of light-heating modulated temperature DTA(HP-LMTDTA) to perform the dynamical thermal measurement of polymers. After construction, we examined performance of the system by using the phase-transitional phenomena of 1,4-trans-polybutadiene crystal to prove it possible to measure the thermal property for the dynamical process during the phase transit … More ion under high-pressure up to 300 Mpa.Through this project, we mainly analyzed the phase-transitional phenomena in nylon and fluoro-copolymer crystals to show that the first- and/or second-order phase transition occurs only in nylon 6Y (Y : even number ≦8) crystals even under normal and high pressure. It was also found that structural changes in vinylidene fluoride(VDF)-trifluoroethylene(TrFE) copolymer crystals are transformed from continuous (cooled phase(CP) to high-temperature phase(HP)) to discontinuous one (low-temperature phase(LP) to HP) with increasing VDF molar content or external pressure for VDF 65 % sample, where the transition from CP to LP occurs prior to the first-order phase transition from LP to HP. The sample with 65 % of VDF is composed of only CP, and LP suddenly appears in VDF 68 % sample and another LP is suggested to exist in VDF 71 and 77 % samples. Percolation theory may be applicable to explain such structural transformation very sensitive with VDF content.Such results indicate that this system can be applied for various studies under high pressure on polymers at molecular level such as crystal growth and melting, formation process of spherulite, electrical properties etc. Less