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

通过DSC测量，对于原样聚（乙烯-共-甲基丙烯酸）及其盐，在50 - 60 ℃和90 ℃附近观察到两个吸热峰，这归因于聚乙烯微晶的熔融。冷却过程中退火后，在略高于退火温度的温度下观察到较低的温度峰。较低的温度峰对应于由退火形成的微晶的熔化，而较高的温度峰对应于由冷却形成的微晶的熔化。离子聚集体的存在阻碍了离聚物的结晶，离子聚集体起交联作用。因此，离聚物的结晶老化，即在室温下退火是比共聚物或低密度聚乙烯显着得多。离<13>聚物结晶区的~ 2C自旋-晶格弛豫时间比聚乙烯短。这一发现表明离聚物中的晶体尺寸比聚乙烯中的小。从实验室和旋转坐标系中^1H自旋扩散与^1H自旋-晶格弛豫时间的讨论中，可以得到离聚物晶体尺寸的类似解释。与乙烯-甲基丙烯酸共聚物相比，甲基丙烯酸分子在离子簇中的迁移受到限制。接着，为了讨论非晶区的运动，进行了自旋探针ESR方法。聚合物基体中自旋探针ESR谱的最外峰分离温度为50 G（T_（？<50G>）），是测定玻璃化转变温度的有用工具。含<50G>TEMPO的离聚物的T_值在低中和和高中和下分别估计为约-20 ℃-20 ℃和-25 ℃。这一发现表明离聚体中存在着非晶区的动力学特征分布，且分布随中和度的变化而变化。

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.