Analysis of Water State and Gelation of Methylcellulose Thermo-reversible Hydrogels by Thermal Analysis and NMR.

The gelation of aqueous methylcellulose (MC) solutions containing polyethylene glycol (PEG) was studied by the combination of differential scanning calorimetry (DSC) and Raman spectrometry. The gelation of MC hydrogels containing PEG occurred in two-steps. First, the gel network was formed by the hydrophobic interaction between MC and PEG at 310 - 313 K, and then, the gel network was formed between MC chains at 323 K. On the other hand, in the MC hydrogels containing PEG and NaCl, sodium ion assumed to be enclosed by PEG, forming a helix with the hydrophobic groups outward. The sodium ion in the gel was expected to be surrounded by the ether oxygen of PEG as crown ether.