Triolo Alessandro, Russina Olga, Hardacre Christopher, Nieuwenhuyzen Mark, Gonzalez Miguel Angel, Grimm Hans
Istituto per i Processi Chimico-Fisici, Consiglio Nazionale delle Ricerche, via La Farina 237, 98123 Messina, Italy.
J Phys Chem B. 2005 Nov 24;109(46):22061-6. doi: 10.1021/jp053355j.
A detailed investigation on the nature of the relaxation processes occurring in a typical room temperature ionic liquid (RTIL), namely, 1-butyl-3-methyl imidazolium hexafluorophosphate ([bmim][PF(6)]), is reported. The study was conducted using both elastic and inelastic neutron scattering over a wide temperature range from 10 to 400 K, accessing the dynamic features of both the liquid and glassy amorphous states. In this study, the inelastic fixed energy scan technique has been applied for the first time to this class of materials. Using this technique, the existence of two relaxation processes below the glass transition and a further diffusive process occurring above the glass-liquid transition are observed. The low temperature processes are associated with methyl group rotation and butyl chain relaxation in the glassy state and have been modeled in terms of two Debye-like, Arrhenius activated processes. The high temperature process has been modeled in terms of a Kohlraush-Williams-Watts relaxation, with a distinct Vogel-Fulcher-Tamman temperature dependence. These results provide novel information that will be useful in rationalizing the observed structural and dynamical behavior of RTILs in the amorphous state.
本文报道了对一种典型室温离子液体（RTIL），即1-丁基-3-甲基咪唑六氟磷酸盐（[bmim][PF₆]）中发生的弛豫过程性质的详细研究。该研究在10至400 K的宽温度范围内使用弹性和非弹性中子散射进行，以探究液态和玻璃态非晶态的动力学特征。在本研究中，非弹性固定能量扫描技术首次应用于这类材料。使用该技术，观察到在玻璃化转变温度以下存在两个弛豫过程，以及在玻璃-液体转变温度以上发生的另一个扩散过程。低温过程与玻璃态下甲基的旋转和丁基链的弛豫有关，并已根据两个类似德拜的阿仑尼乌斯活化过程进行建模。高温过程已根据科尔劳施-威廉姆斯-瓦特弛豫进行建模，具有明显的沃格尔-富尔彻-塔曼温度依赖性。这些结果提供了新的信息，将有助于合理解释非晶态RTILs中观察到的结构和动力学行为。
