A Study on Higher-order Structures and Dynamics of Ionic Aggregates in Ionomers

离聚物被定义为具有非极性骨架的聚合物，含有高达约10 mol%的羧基或磺酸盐基团。因此，可以说离聚体是一种杂化材料。离子聚体可以形成离子聚集体，提高了材料的力学性能。在镉盐乙烯离聚体中，通过SAXS分析证实了离子聚集体的形成。离子聚合体的大小随着中和度的增大而增大。这与其他使用二价金属阳离子（如锌阳离子）的乙烯离聚物相比是不同的一点。观察了镉盐乙烯离聚体在不同温度下有CP实验和无CP实验时的^<113>Cd MAS光谱。在CP/MAS光谱中，只有在低温下才能观察到一个非常宽的峰。可以看出，这些光谱由出现在约120至-50 ppm的几个峰组成。因此，该峰的展宽可能主要是由于离子聚集体中^<113>Cd核周围的微结构分布非常广泛。在较高温度下，该CP/MAS峰消失，表明^<113>Cd核在偶极去耦频率附近的迁移率和/或CP效率变得太低而无法检测CP信号，因为^<113>Cd周围的1H核的高迁移率。即镉盐乙烯离聚体中的离子聚集体通过加热由不动态变为可动态。相反，没有CP实验的^<113>Cd MAS NMR谱只在高温下观测到，且与CP/MAS相比，观测到的峰宽相对较窄。此外，^<113>Cd核磁共振化学位移随温度变化。这些发现表明，离子聚集体在较高温度下的迁移率较高。

The ionomers are defined as polymers with non-polar backbones containing up to about 10 mol% salt groups of carboxyl or sulfonic acids. It can be, therefore, said that the ionomers is one of the hybrid materials. The ionomers can form the ionic aggregates, which improve the mechanical properties of them. In cadmium salt ethylene ionomers, it is confirmed that the ionic aggregates are also formed, from SAXS analysis. The size of the ionic aggregates of this ionomer becomes larger with the degree of neutralization. This is a different point in comparing with the other ethylene ionomers using divalent metal cations such as zinc cation. The ^<113>Cd MAS spectra with and without CP experiment for cadmium salt ethylene ionomer at various temperatures were observed. In CP/MAS spectra, a very broad peak is only observed at low temperatures. It can be seen that these spectra consists of several peaks appeared at about 120 to -50 ppm. Consequently, the broadening of this peak may be mainly caused by the very wide distribution of micro structures at surroundings of^<113>Cd nuclei in the ionic aggregates. At higher temperatures, this CP/MAS peak disappears, indicating that the mobility of ^<113>Cd nuclei close to the dipolar decoupling frequency and/or the CP efficiency becomes too low to detect the CP signals because of the high mobility of 1H nuclei at surroundings of ^<113>Cd. That is, the ionic aggregates in cadmium salt ethylene ionomers leads to mobile state from immobile one by heating. On the contrary, the ^<113>Cd MAS NMR spectra without CP experiment are observed only at high temperatures, and the width of observed peaks are relatively narrow compared with CP/MAS. In addition, the ^<113>Cd NMR chemical shift changes by temperature. These findings indicate that the mobility of the ionic aggregates is high at higher temperatures.