Identification of the slower secondary relaxation's nature in maltose by means of theoretical and dielectric studies.

Dielectric relaxation measurements on maltose were performed at ambient and increasing pressure. The loss spectra collected below glass transition of this disaccharide revealed presence of two well separated secondary relaxations. Activation energies determined for both modes are E(a)=73 kJ/mol and 47 kJ/mol for the slower (beta) and faster (gamma) relaxation, respectively. From high pressure measurements activation volume DeltaV=15.6 ml/mol for the slower secondary relaxation was estimated. Both quantities: activation energy and activation volume for alpha-process derived from dielectric data, were compared to those obtained from the conformational calculations with use of density functional theory (DFT). We found out satisfactory agreement between both quantities for the molecular motion related to the rotation of the two monosaccharide units around glycosidic linkage in this disaccharide.