A transparent gel was prepared through the cooling of a methylcellulose (MC) solution in N,Ndimethylformamide (DMF) at 808C 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.

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The effect of highly substituted cationic cetyl trimethyl ammonium bromide (CTAB), less substituted cationic hexadodecyl ammonium bromide (HDAB), CTABand HDAB-modified montmorillonite (CTABMONT and HDABMONT), and nonionic surfactants on the rheological properties of methylcellulose (MC) N,N-dimethylformamide (DMF) gels have been studied. The storage modulus of the MC-MDF gels increases with an increase in frequency. During the frequency scan, the storage and loss modulus of MC-DMF gel crosses over each other at two different frequencies. At the crossover points, the loss tangent is found to be unity. The addition of CTAB-and HDAB-modified nanofiller increases in the gel strength of MC-DMF gel. The storage modulus of MC-DMF gel in the presence of CTABMONT is found to be higher than that of CTAB-modified MC-DMF gel. Whereas, the storage modulus of MC-DMF gel in the presence of HDABMONT is lower than that of HDAB-modified MC-DMF gel. On the other hand, the addition of nonionic surfactant (Brij78) decreases the gel strength.

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