Inverse freezing in α-cyclodextrin solutions probed by quasi elastic neutron scattering

Solutions of α-cyclodextrin, 4-methylpyridine and water undergo a reversible liquid–solid phase transition on heating (“inverse freezing”). In this paper quasi elastic neutron scattering (QENS) measurements are reported, from which the diffusive dynamics of different components in the liquid and solid phases is determined. Results imply that, in solution, α-cyclodextrin is contained in a solvation shell of 4-methylpyridine molecules, while in the crystal phase, the majority of the cell contents are immobilized on the nanosecond timescale. This information will be important in evaluating the entropy of the system in its different phases and in understanding the unusual phase transition.