Complexity of structural and dynamic features in RTILs

Room temperature ionic liquids (RTILs) are characterised by the coexistence of polar and apolar moieties. The different nature of the interaction between these moieties leads to a complex morphology, as the apolar part (typically represented by alkyl chains) tend to segregate into nm-scale clusters that are embedded into a three-dimensional charged (polar) network. Such a behaviour was originally proposed in the basis of molecular dynamics simulations and confirmed on the basis of experimental data. We will report on X-ray and neutron diffraction experiments highlighting the existence of nano-scale structural heterogeneities in a variety of RTILs. Furthermore, we will show that this complex morphology has strong implications on the relaxation dynamics in these systems. Using Neutron Spin Echo, dielectric and mechanical spectroscopies we will highlight the existence of relaxation processes whose activation energy depends upon the size of the structural heterogeneities.