Influence of Counterion Structure on Conductivity of Polymerized Ionic Liquids
Influence of Counterion Structure on Conductivity of Polymerized Ionic Liquids
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DOI：
10.1021/acsmacrolett.9b00070
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发表时间：
2019-04-01
影响因子：
7.015
通讯作者：
Ganesan, Venkat
中科院分区：
文献类型：
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作者：
Keith, Jordan R.;Rebello, Nathan J.;Ganesan, Venkat
我们进行了长时间的全原子分子动力学模拟的阳离子聚合的离子液体与8个移动的抗衡离子，系统地改变大小和形状，以探讨其对解耦的电导率从聚合物链段动力学的影响。我们使用全原子力场证明了聚合离子液体的膨胀玻璃化转变温度（T-g）的严格识别。聚合物链段弛豫速率被认为是一致的不同材料在相同的玻璃化转变标准化温度（T-g/T），使我们能够提取一个相对的顺序去耦通过检查电导率在相同的T-g/T。尺寸或离子体积不能完全解释退耦趋势，但在某些几何和化学特定类别中，小离子通常表现出更高程度的退耦。这种尺寸效应是不普遍的，似乎是克服结构的结果显示大量的协调离域。我们还揭示了这些聚合离子液体的离子缔合结构弛豫时间和绝对电导率之间的普遍负相关性，支持聚合离子液体中离子迁移率的离子跳跃解释。
We performed long-time all-atom molecular dynamics simulations of cationic polymerized ionic liquids with eight mobile counterions, systematically varying size and shape to probe their influence on the decoupling of conductivity from polymer segmental dynamics. We demonstrated rigorous identification of the dilatometric glass transition temperature (T-g) for polymerized ionic liquids using an all-atom force field. Polymer segmental relaxation rates are presumed to be consistent for different materials at the same glass-transition-normalized temperature (T-g/T), allowing us to extract a relative order of decoupling by examining conductivity at the same T-g/T. Size, or ionic volume, cannot fully explain decoupling trends, but within certain geometric and chemical-specific classes, small ions generally show a higher degree of decoupling. This size effect is not universal and appears to be overcome when structural results reveal substantial coordination delocalization. We also reveal a universal inverse correlation between ion-association structural relaxation time and absolute conductivity for these polymerized ionic liquids, supporting the ion-hopping interpretation of ion mobility in polymerized ionic liquids.