Rheology of viscoelastic solutions of cationic surfactant. Effect of added associating polymer.
Rheological studies were performed with aqueous salt solutions of viscoelastic cationic surfactant erucyl bis(hydroxyethyl)methylammonium chloride (EHAC) and its mixtures with hydrophobically modified polyacrylamide. The solutions of surfactant itself above the concentration of crossover of wormlike micelles exhibit two regions of rheological response. In the first region, they behave like polymer solutions in semidilute regime characterized by viscoelastic behavior with a spectrum of relaxation times. In the second region, unlike polymer solutions their relaxation after shear is dominated by a single relaxation time. Being composed of "living" micelles, the EHAC solutions easily lose their viscosity at the variation of the external conditions. For instance, heating from 20 to 60 degrees C reduces viscosity by up to 2 orders of magnitude, while added hydrocarbons induce a sudden drop of viscosity by 3-6 orders of magnitude. Polymer profoundly affects the rheological properties of EHAC solutions. The polymer/surfactant system demonstrates a 10,000-fold increase in viscosity as compared to pure-component solutions, the effect being more pronounced for polymer with less blocky distribution of hydrophobic units. A synergistic enhancement of viscosity was attributed to the formation of common network, in which some subchains are made up of elongated surfactant micelles, while others are composed of polymer. At cross-links the hydrophobic side groups of polymer anchor EHAC micelles. In contrast to surfactant itself, the polymer/surfactant system retains high viscosity at elevated temperature; at the same time it keeps a high responsiveness to hydrocarbon medium inherent to EHAC.
Shashkina
Julia A
JA
Physics Department, Moscow State University, 119992 Moscow, Russia.
Philippova
Olga E
OE
Zaroslov
Yuri D
YD
Khokhlov
Alexei R
AR
Pryakhina
Tatyana A
TA
Blagodatskikh
Inessa V
IV
D002412:Cations / Q000737:chemistry; D004548:Elasticity; D004883:Erucic Acids / Q000737:chemistry; D008823:Micelles; D015394:Molecular Structure; D011108:Polymers / Q000737:chemistry*; D000644:Quaternary Ammonium Compounds / Q000737:chemistry; D012212:Rheology; D012996:Solutions; D013057:Spectrum Analysis; D013499:Surface Properties; D013501:Surface-Active Agents / Q000737:chemistry*; D013696:Temperature; D014783:Viscosity
D002412:Cations; D004883:Erucic Acids; D008823:Micelles; D011108:Polymers; D000644:Quaternary Ammonium Compounds; D012996:Solutions; D013501:Surface-Active Agents; C509663:erucyl bis(hydroxyethyl) methylammonium chloride