Dependence of Molecular Weight on Phase Diagram of Methyl Cellulose Solution Showing Thermoreversible Gelation

• Published in: KOBUNSHI RONBUNSHU 1998/05/25, Vol.55(5), pp.269-276
• Main Authors: TAKAHASHI, Masae, SHIMAZAKI, Masako, YAMAMOTO, Jun
• Format: Article
• Language: Japanese
• Subjects: Methyl Cellulose; Micro Differential Scanning Calorimetry; Molecular Weight; Phase Diagram; Phase Separation; Sol-Gel Transition
• ISSN: 0386-2186; 1881-5685
• DOI: 10.1295/koron.55.269

We attempted to draw up typical phase diagrams showing co-occurrence of gelation and phase separation using methylcellulose (MC) samples having different molecular weights, with micro differential scanning calorimetry (DSC) and visual inspection. Furthermore, the junction multiplicity s and the junction length ζ were estimated for analyzing the junction structure. The phase diagrams qualitatively agreed well with the theoretically calculated ones. The sol-gel transition and phase separation lines shifted toward lower temperatures and lower concentrations with increasing molecular weight. It was expected that the sol-gel transition line intersects at a higher temperature than the critical point of the phase separation line, and therefore in the phase separation regime, there would exist two regimes, which are the sol-gel phase separation and the gel-gel phase separation. Practically in a visual inspection of MC-4 sample in the critical temperature region, we observed the gel-gel phase separation. It was suggested that the network junction of MC gels consist of crystalline sequences with 25-50 monomeric units.