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

目前国际上还没有严格证明聚合物晶体中出现二阶相变的报道。我们最近在高压x射线结构分析的基础上发现了聚酰胺晶体的二阶相变。通过这些研究，我们注意到国际上还没有对高压下比热测量进行定量分析，这必须为我们讨论材料的相变现象提供最重要的信息之一。这就是我们开始这个项目的原因。本课题的第一步是构建光热调制温度DTA高压系统（HP-LMTDTA），对聚合物进行动态热测量。构建完成后，我们利用1,4-反式聚丁二烯晶体的相变现象对系统的性能进行了测试，证明了在高达300 Mpa的高压条件下测量离子相变动力学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，表明即使在正常和高压下，只有尼龙6Y （Y：偶数≦8）晶体才会发生一级和/或二级相变。在VDF含量为65%的样品中，随着VDF摩尔含量或外部压力的增加，偏氟乙烯-三氟乙烯（TrFE）共聚物晶体的结构变化由连续相（冷却相（CP）→高温相（HP））→不连续相（低温相（LP）→HP），其中从CP到LP的转变发生在从LP到HP的一级相变之前。含有65% VDF的样品仅由CP组成，而在VDF 68%样品中突然出现LP，而在VDF 71和77%样品中可能存在另一种LP。渗流理论可以解释这种对VDF含量非常敏感的结构变化。这些结果表明，该系统可以应用于聚合物在高压下的分子水平上的各种研究，如晶体生长和熔化、球晶的形成过程、电学性质等。少

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