Vibrational and relaxational contributions in disaccharide/H2O glass formers

Abstract

Among oligosaccharides, trehalose seems to be unique in nature as a bioprotector in drying and freezing processes. To understand the molecular mechanisms underlying the unusual bioprotective properties of trehalose in comparison with other disaccharides, the low-frequency dynamics of aqueous $({\mathrm{H}}_2\mathrm{O}$ and ${\mathrm{D}}_2\mathrm{O})$ mixtures of homologous disaccharides, trehalose, and sucrose has been studied by neutron scattering measurements carried out using the Mibemol spectrometer at the Laboratoire Leon Brillouin (LLB, Saclay). The principal aim of this work is to compare the relaxational versus low-energy vibrational contributions of ${\mathrm{s}\mathrm{u}\mathrm{c}\mathrm{r}\mathrm{o}\mathrm{s}\mathrm{e}/\mathrm{H}}_2\mathrm{O}$ and ${\mathrm{t}\mathrm{r}\mathrm{e}\mathrm{h}\mathrm{a}\mathrm{l}\mathrm{o}\mathrm{s}\mathrm{e}/\mathrm{H}}_2\mathrm{O}$ mixtures across the glass transition, in order to characterize, following a procedure first proposed by Sokolov and co-workers, the different “fragile” character of both the ${\mathrm{d}\mathrm{i}\mathrm{s}\mathrm{a}\mathrm{c}\mathrm{c}\mathrm{h}\mathrm{a}\mathrm{r}\mathrm{i}\mathrm{d}\mathrm{e}/\mathrm{H}}_2\mathrm{O}$ mixtures.