Effect of addition of surfactants on the rheology of gels from methylcellulose in N,N-dimethylformamide

The effect of highly substituted cationic cetyl trimethyl ammonium bromide (CTAB), less substituted cationic hexadodecyl ammonium bromide (HDAB), CTAB‐ and 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. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008