Thermogelation of Methylcellulose from Solution in N,N-Dimethylformamide and Characterization of the Transparent Gels

A transparent gel was prepared through the cooling of a methylcellulose (MC) solution in N,N-dimethylformamide (DMF) at 80 degrees C to a lower temperature. The temperature at which gelation occurred was dependent on the concentration of the solution. The gel temperature increased with an increase in the concentration of MC. The gelation of MC in DMF was studied by means of optical microscopy (OM), differential scanning calorimetry, and dynamic mechanical analysis (DMA). The OM studies revealed the presence of loosely bound beads of MC with DMF at a lower concentration. These beads became interconnected to rods, and subsequently, a continuous, thick gel was formed as the concentration increased. From DMA studies, it was observed that the loss modulus of the gel crossed over the storage modulus at two different frequencies. This indicated the presence of two types of network structures generated from the weak and strong associations of MC with the organic solvent DMF. (C) 2008 Wiley Periodicals, Inc. J Appl Polym Sci 110: 3031-3037,2008