Carbon-13 nuclear magnetic relaxation in supercooled liquid and glassy maltose

Abstract

¹³ C longitudinal relaxation rates (T₁^-1) in highly viscous liquid and solid amorphous maltose, its mixtures with water and methanol, and also crystalline maltose monohydrate, have been measured as a function of temperature, above and below the calorimetric glass transition temperatures of the amorphous materials. From the results it is concluded that, at temperatures up to 60°C below the glass transition temperature, the carbon atoms in the exocyclic hydroxymethyl groups of maltose are more mobile than the endocyclic carbon atoms. A few percent of water is sufficient to considerably enhance amorphous maltose mobility. At temperatures close to the glass transition methanol in amorphous maltose–methanol mixtures retains a high degree of rotational mobility which is decoupled from the bulk viscosity.