Molecular dynamics (MD) simulations are performed using a coarse-grained model of polyampholyte ionomers in which both types of ions are incorporated in the polymer chain and, consequently, the ion-pairs form bridges across the chains (i.e., bridged ion-pair) and compared their dynamics and structures with the conventional cationic ionomers, where only cations are incorporated into the polymer chain (e.g., pendant ion-pair). While the glass transition temperatures of both structures are comparable, mesoscale ordering within large, string-like aggregates is observed in the polyampholyte (bridged) ionomer instead of square-like aggregates in the cationic (pendant) ionomer. Both systems show dynamical heterogeneities at temperatures above T_g, which persist at higher temperatures for the bridged ionomers. A linear correlation between the lifetime of the ionic bonds and the dynamic relaxation time over a wide temperature range is observed. A comparison of these time scales showed that ions have collective dynamics in the bridged ionomers. Furthermore, the intermediate scattering function data obtained at different temperatures can collapse onto master curves, which confirms the applicability of the time–temperature superposition principle in these structures. Overall, this study shows that modifying the chain connectivity of the ion-pairs provides an alternative route to control the morphology and dynamics of ionomers.

中文翻译：

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聚两性电解质和阳离子离聚物的微观形态和动力学

分子动力学 (MD) 模拟使用聚两性电解质离聚物的粗粒度模型进行，其中两种类型的离子都纳入聚合物链中，因此离子对在链上形成桥（即桥接离子对）并将它们的动力学和结构与传统的阳离子离聚物进行了比较，其中仅将阳离子掺入聚合物链中（例如，侧离子对）。虽然两种结构的玻璃化转变温度相当，但在聚两性电解质（桥联）离聚物中观察到大的线状聚集体内的介观有序，而不是在阳离子（悬垂）离聚物中观察到方形聚集体。两个系统在高于T _{g 的}温度下都表现出动态异质性，对于桥联离聚物来说，这种异质性在更高的温度下仍然存在。在很宽的温度范围内观察到离子键的寿命和动态弛豫时间之间的线性相关性。这些时间尺度的比较表明，离子在桥联离聚物中具有集体动力学。此外，在不同温度下获得的中间散射函数数据可以折叠到主曲线上，这证实了时间-温度叠加原理在这些结构中的适用性。总的来说，这项研究表明，改变离子对的链连接性提供了控制离聚物形态和动力学的替代途径。