Abstract
The behavior of glass transition of polysaccharide electrolyte-water systems was investigated by differential scanning calorimetry (DSC). Samples used in this report are sodium cellulose sulfate (NaCS), sodium carboxymethylcellulose (NaCMC), xanthan gum (Xan), sodium hyaluronate (NaHA), and sodium alginate (NaAlg). The above polysaccharide-water systems showed glass transition in the water content, Wc [= (weight of water) / (weight of dry sample), (g/g)] ranging from almost 0 to 3.0. The DSC observation leads to the following conclusions: (1) when water molecules are bound to hydrophilic groups and counter ions of polysaccharides as non-freezing water, glass transition temperature (Tg) was observed in a wide temperature range between 180 to 350 K depending on Wc, (2) although the amount of non-freezing water was dependent on the chemical structure of each polysaccharide, the minimum value of the Tg of each polysaccharide-water system was very similar and was 180+5 K, (3) the above Tg minimum was observed in the Wc range when the amount of non-freezing water (Wnf) became maximum in each polysaccharide-water system, and (4) the NaHA-water system showed lower Tg than the other polysaccharide-water systems because of its specific chemical structure.
