文摘
When considering the ionic liquids (ILs) in general, and especially the room temperature ionic liquids (RTIL), the interest is naturally focused on the ionic conductivity and ion dynamics. Nonetheless, many ionic liquids are glass-formers, and undergo glass transition at T g on cooling at ambient pressure or at P g on elevating the applied pressure P at constant temperature. In the supercooled liquid state, both the structural relaxation and the ionic conductivity relaxation are present and observable. Thus glass-forming ILs confer the bonus of studying ionic conductivity relaxation and structural relaxation in the same material. If the two processes are decoupled, the relation between the structural relaxation and the conductivity relaxation, and possible effect of the former on the latter is of interest in basic research as well as in applications. Some general and interesting properties of the two relaxation processes are brought out in this chapter. The challenge to theory is the explanation of not only the properties of the conductivity relaxation but also the structural relaxation, and their relations. As it turns out, the properties of the two relaxation processes are similar, indicating that they stem from some common physics that bridge the two fields. Proposed specifically for ionic conductivity relaxation and diffusion, some theory or model may run into difficulty in adapting it to explain the similar property of structural relaxation and viscosity of glass-formers. This problem casts doubt on the physics of the theory because it is common to the two fields, and a viable theory proposed in one field should be easy in adapting to the other field. Therefore it is beneficial for those engaged in research of ionic conductivity relaxation and particularly in ionic liquids to be aware of the wealth of properties of glass-forming systems and the explanations.