Rheometric and rheo-optical investigation on the effect of the aliphatic chain length of the surfactant on the shear thickening of dilute worm-like micellar solutions |
| |
Authors: | Jalal Dehmoune Jean-Paul Decruppe Olivier Greffier Hong Xu |
| |
Institution: | (1) Laboratoire de Physique des Milieux Denses, Groupe des Fluides Complexes, IPEM, 1 Bd. F. Arago, 57078 Metz, France |
| |
Abstract: | In this study, a new way of understanding the shear-thickening phenomenon in self-assembled solutions is introduced. The near-
and out-of-equilibrium behavior is investigated in four aqueous micellar solutions containing surfactants of the same family:
the alkyltrimethylammonium bromide mixed with an ionic salt at equimolar concentration. Thus, the four molecules of surfactants
have the same polar head but different aliphatic chain length containing 12, 14, 16, and 18 carbon atoms. In aqueous solutions,
the attractive forces between the surfactant molecules depend on the length of the aliphatic chain, thus, varying this parameter
will have a definite influence on the aggregation number, the shape and dimension of the micelles. According to our results,
the evolution of the low shear viscosity is affected by the chain length. The rheometric measurements performed in steady
and time-dependent flows show that the emergence, the range, and the amplitude of the shear thickening also depend on this
parameter. However, in the domain of high shear rates, after reaching the maximum of viscosity, all flow curves superimpose
irrespective of the chain length. The rheo-optic measurements confirm the apparition of the shear-induced structure (SIS);
this new phase is locally oriented and the chain length affects strongly the micelles orientation and the birefringence intensity.
These results undoubtedly demonstrate that the chain length plays an important role in the behavior near equilibrium and under
shear flow of the micellar systems.
Paper presented at the third Annual European Rheology Conference (AERC 2006) on April 27–29, 2006, Crete, Greece. |
| |
Keywords: | Shear-induced structure Couette flow Strain- and stress-controlled modes Stationary flow Rheometry Rheo-optic |
本文献已被 SpringerLink 等数据库收录! |
|