Detection of Water State in Methylcellulose Thermo Reversible Hydrogels using Melting of a Eutectic

摘要

Polyethylene glycol (PEG) is considered environmentally and biologically friendly materials, and has been applied to industrial or biological use as a highly hydrophilic and viscous polymer. PEG-water systems form a eutectic of PEG and water. PEG-water systems in various molar ratios of ethylene oxide (EOX) (constitutional repeating unit of PEG) to H_2O were investigated by DSC, NIR (Near infrared spectroscopy) and ~(17)O NMR, in order to investigate the behavior of water molecules in PEG hydrogel. The results of melting peak of eutectics of PEG and water show the good agreement with those of NIR, NMR measurements. PEG-methylcellulose (MC) -water system forms thermo reversible gel in heating process. We found that the memory of the gel state was keeping for 3 days after gelling. The interaction of PEG and water was gradually weakened by addition of MC and was reached at steady state at the low molar fraction region. In this study, the MC-saltwater system at the water-rich region, the water state was investigated. We found that the memory of the gel state was keeping for several days after gelling of MC-salt-water system. The keeping period was influenced by cation. The keeping period of MC-CsCl-water system was the longest. The period of keeping the memory of the gel state after gelling agreed with the strength of MC-salt interaction in the gel state. It was considered that the hydrophobic interaction of MC with cesium ion was related to the mechanism of the gel state.