STUDY ON CRITICAL PHENOMENA IN POLYMER CRYSTALS BASED ON LIGHT-HEATING MODULATED TEMPERATURE DIFFERENTIAL SCANNING CALORIMETRY UNDER HIGH PRESSURE

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和偏氟乙烯/三氟乙烯共聚物晶体的二阶相变。通过这些研究，我们发现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。本课题的目的是将高压技术与光加热调制温差扫描量热计（HP-LMTDSC系统）相结合，构建一套能够对聚合物比热进行定量精确测量的系统，并对上文提到的一些聚合物晶体进行相变研究。2000年，我们尝试构建了基本的HP-LMTDSC，并研究了频率、温度和压力变化时的信噪比特性，发现在0时可以获得最大信号。1hz和环境介质影响结果。样品空间的温度和压力被确定提高到300℃和300 Mpa。2001年，我们改进了系统性能。为了使入射光强度呈正弦变化，设置了两块偏振片，其中一块固定，另一块旋转。采用7个铜-康铜热电偶串联，提高了测温灵敏度。利用该系统，在0.025 Hz和1 ~ 750 atm条件下测量了无规聚苯乙烯玻璃化转变温度Tg的压力依赖性，发现Tg随压力增大而增大。结果表明，该系统可应用于高分子材料在高压下的晶体生长和熔融、球晶形成过程、电学性能等方面的研究。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 crystals of polyamide and vinylidene fluoride/trifluoroethylene copolymer on the basis of X-ray structure analysis under high-pressure. Through such studies, we found 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 object of this project is to construct the system to perform the quantitative and precise measurement of the specific heat of polymers by combining the high-pressure technique and light-heating modulated temperature differential scanning calorimeter (HP-LMTDSC system) as well as development of the phase-transitional study for some polymer crystals as-mentioned ab … More ove.In 2000, we tried to construct the basic HP-LMTDSC and examine the S/N characteristic with changing frequency, temperature and pressure to find that the maximum signal can be gained at 0. 1 Hz and the environmental medium affects the results. Temperature and pressure in the sample space was confirmed to be raised up to 300℃ and 300 Mpa.In 2001, we improved the system property. In order to change the incident light intensity sinusoidally, two polarizer plates were set, where one plate was fixed and the another rotated. Sensitivity of temperature measurement was increased by arranging seven Cu-constantan thermocouples in series.By using this system, pressure dependence of glass transition temperature Tg of atactic polystyrene was measured at 0.025 Hz and at 1-750 atm to find that Tg increased with pressure. The result shows that this system can be applied for various study under high pressure on polymers at molecular level such as crystal growth and melting, formation process of spherulite, electrical properties etc. Less