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.
Keywords: 1H nuclear magnetic relaxation times; BET: Burnuer, Emmett and Teller; BPP: Bloembergen, Purcell and Pound; CMC: carboxymethylcellulose; CS: cellulose sulfate; Cp: heat capacity; DS: degree of conversion; DSC: differential scanning calorimetry; NFP: non-freezing protein; NMR: nuclear magnetic resonance; NaCMC: sodium carboxymethylcellulose; NaCS: sodium cellulose sulfate; PHEMA: poly(hydroxyethylmethacrylate); PMEA: poly(2-methoxyethyl acrylate); PMPC: poly(2-methacryloyloxyethyl phosphorylcholine); PTHFA: poly(tetrahydrofurfuryl acrylate); Polysaccharide; RH: relative humidity; T1: spin-lattice (longitudinal) relaxation time; T2: spin-spin (transverse) relaxation time; Tc: crystallization temperature; Tg: glass transition temperature; Tm: melting temperature; Wc: water content; Wfb: freezing bound water; Wnf: non-freezing water content; heat capacity; non-freezing water; ΔCp: heat capacity difference at Tg; ΔHc: enthalpy of crystallization; ΔHm: enthalpy of melting; τc: correlation time.