A Study on Higher-Order Structure and Molecular Motions of the ionic cluster in ionomer

通过DSC测量，在50 ~ 60℃和90℃范围内，聚乙烯-共甲基丙烯酸及其盐的两个吸热峰归因于聚乙烯晶体的熔融。在冷却过程中退火后，在略高于退火温度的温度处观察到较低的温度峰。较低的温度峰对应于退火形成的晶体的熔化，较高的温度峰对应于冷却形成的晶体的熔化。离子聚集体的存在阻碍了离子单体的结晶，离子聚集体起交联作用。因此，在室温下退火的离子单体的结晶比共聚物或低密度聚乙烯的结晶要显著得多。离聚物晶体区的^<13>C自旋晶格弛豫时间比聚乙烯短。这一发现表明，离子单体的晶体尺寸比聚乙烯小。在实验室和旋转框架中讨论了^1H自旋扩散和^1H自旋晶格弛豫时间，得到了对离子单体晶体尺寸的类似解释。另一方面，与乙烯-甲基丙烯酸共聚物相比，甲基丙烯酸分子在离子团簇中的迁移率受到限制。其次，采用自旋探针ESR法讨论了非晶区的运动。自旋探针在聚合物基体中的ESR谱最外峰的分离温度为50G (T_<50G>)，是测定Tg的一个有价值的工具。在低中和和高中和条件下，含tempo的离聚物的T_<50G>分别约为-20 -20和-25‰。这一发现表明，非晶态区域的动力学特征在离子单体中是有分布的，且分布随中和作用的变化而变化。

Two endothermic peaks observed by DSC measurement around 50 - 60 ﾟC and 90 ﾟC for as received poly(ethylene-co-methacrylic acid) and its salts were attributed to the melting of polyethylene crystallites. After annealing in the cooling process, the lower temperature peak was observed at a temperature slightly higher than the annealing temperature. The lower temperature peak corresponded to the melting of the crystallites formed by the annealing and the higher one to that by cooling. The crystallization of ionomer is hindered by the presence of ionic aggregates which play a role of crosslinking. Consequently the crystallization of ionomer aged, that is, annealed at room temperature is much more remarkable than that of the copolymer or low density polyethylene. The ^<13>C spin-lattice relaxation time of the crystalline region of ionomer was shorter than that of polyethylene. This finding is suggested that size of crystal in the ionomers were relatively small than that in polyethylene. Similar interpretations on the crystal size of the ionomers were obtained from the discussion about ^1H spin-diffusion with ^1H spin-lattice relaxation times in the laboratory and rotating frames. On the other hand, the mobility of methacrylic molety in the ionic cluster was restricted in comparison with that in ethylene-methacrylic acid copolymer. Next, to discuss the motion of amorphous region, spin-probe ESR method was carried out. The temperature at which the separation of the outmost peaks of the ESR spectrum of spin-probe in polymer matrix is 50G (T_<50G>), is a valuable tool for Tg determination. The values of T_<50G> for TEMPO-containing ionomers were estimated to be about -20 ﾟC - 20 ﾟC and -25 ﾟC at low and high neutralization, respectively. This finding show that there is the distribution of the dynamical features of amorphous region in the ionomer, and the distribution changes with the neutralization.