Heat capacity and nuclear magnetic relaxation times of non-freezing water restrained by polysaccharides, revisited

Abstract

Calorimetric and nuclear magnetic relaxation studies on non-freezing water restrained by polysaccharide are introduced together with the historical background of this research field. Non-freezing water restrained by the hydrophilic group of polysaccharide shows no first order thermodynamic phase transition. The amount of non-freezing water calculated from the melting enthalpy of water restrained by various kinds of polysaccharides was collected. Molecular motion of polysaccharides is markedly enhanced by the introduction of non-freezing water and glass transition shifts to the ca. 200 K low temperature side. At the same time, molecular chains rearrange to a more stabilized state, which can be observed as the decrease in heat capacities. 1H nuclear magnetic relaxation studies at a temperature lower than glass transition indicate that a part of the water molecules is closely bound to the backbone proton and is not sufficiently isolated. Calorimetric and nuclear magnetic relaxation studies suggest that non-freezing water inevitably cooperates with matrix polysaccharide molecules.