Observation of Microheterogeneity in Highly Concentrated Nonaqueous Electrolyte Solutions.

The development of models to describe structure and dynamics of nonaqueous electrolyte solutions is challenging, and experimental observations are needed to form a foundation. Here, neutron scattering is used to probe molecular dynamics in nonaqueous organic electrolytes. Two solutions were compared: one contained symmetrical electrolyte molecules prone to crystallize, and one contained desymmetrized electrolyte molecules preferring disordered states. For the latter, calorimetry and neutron data show that a disordered fluid persists to very low temperatures at high concentrations. Upon heating, localized cold crystallization occurs, leading to burst nucleation of microcrystalline solids within fluid phases. Our findings indicate molecular clustering and point to solvation inhomogeneities and molecular crowding in these concentrated fluids.