Microscopic insights into ion gel dynamics using neutron spectroscopy
Microscopic insights into ion gel dynamics using neutron spectroscopy
复制标题
DOI：
10.1039/c2sm25348h
复制
发表时间：
2012-07
期刊：
影响因子：
3.4
通讯作者：
M. Kofu;T. Someya;S. Tatsumi;K. Ueno;T. Ueki;M. Watanabe;T. Matsunaga;M. Shibayama;V. G. Sakai;M. Tyagi;O. Yamamuro
中科院分区：
文献类型：
--
作者：
M. Kofu;T. Someya;S. Tatsumi;K. Ueno;T. Ueki;M. Watanabe;T. Matsunaga;M. Shibayama;V. G. Sakai;M. Tyagi;O. Yamamuro
我们通过准弹性中子散射（QENS）研究了由 PMMA [聚（甲基丙烯酸甲酯）] 网络和 EMITFSI [1-乙基-3-甲基咪唑鎓双（三氟甲磺酰）亚胺] 作为离子液体组成的离子凝胶的微观动力学。有趣的是，这些离子凝胶表现出两个玻璃化转变温度 (Tgs)，随着离子液体含量的增加，玻璃化转变温度急剧下降。 QENS 使我们能够通过选择性氘化各个组分来分别探测 PMMA 和 EMI [1-乙基-3-甲基咪唑鎓] 阳离子的动力学，并深入了解该系统的玻璃特性。对 QENS 光谱进行了全面分析，揭示了许多特征弛豫，包括分子内弛豫，每一个都被指定。我们发现PMMA扩散的活化能随着离子液体含量的增加而降低，这与聚合物的塑化相对应。离子液体表现出两个特征弛豫：与PMMA运动强烈耦合的运动，我们认为这是与PMMA结合的离子液体部分的运动，产生更高的有效Tg；以及与远离聚合物链的离子液体分子相关的离子扩散，其行为几乎与自由液体一样，表现出较低的Tg。
We have investigated the microscopic dynamics of ion gels consisting of a PMMA [poly(methyl methacrylate)] network and EMITFSI [1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide] as the ionic liquid by means of quasi-elastic neutron scattering (QENS). These ion gels interestingly exhibit two glass transitions (Tgs) which drastically decrease as the ionic liquid content increases. QENS allows us to probe the dynamics of PMMA and the EMI [1-ethyl-3-methylimidazolium] cation separately, by selectively deuterating the individual components, and gain insight into the glassy properties of this system. A comprehensive analysis of the QENS spectra was performed, revealing a number of characteristic relaxations, including intramolecular ones, each of which was assigned. We found that the activation energy for PMMA diffusion decreases with increasing ionic liquid content, corresponding to the plasticization of the polymer. The ionic liquid showed two characteristic relaxations: a motion strongly coupled to the motion of PMMA which we argue to be the motion of part of the ionic liquid which is bound to the PMMA giving rise to a higher effective Tg and an ionic diffusion associated with ionic liquid molecules far from the polymer chains which behave nearly as free liquid, exhibiting a lower Tg.