Rheology, Cryogenic Transmission Electron Spectroscopy, and Small-Angle Neutron Scattering of Highly Viscoelastic Wormlike Micellar Solutions

• Published in: Langmuir 2003-09, Vol.19 (20), p.8536-8541
• Main Authors: Croce, Vania, Cosgrove, Terence, Maitland, Geoff, Hughes, Trevor, Karlsson, Göran
• Format: Article
• Language: English
• ISSN: 0743-7463; 1520-5827
• DOI: 10.1021/la0345800

To understand the strong viscoelastic response showed by aqueous solutions of erucylbis(hydroxyethyl)methylammonium chloride (EHAC) in the presence of potassium chloride (KCl), steady-state rheology, small-angle neutron scattering (SANS), and cryogenic transmission electron microscopy (cryo-TEM) experiments were performed. This cationic surfactant has the ability to self-assemble into giant wormlike micelles. The effect of surfactant concentration, added salt, and temperature were investigated. The surfactant solutions have a gellike behavior at room temperature and become Maxwellian as the temperature is increased. It was found that the low-shear viscosity has a strong dependence on salt concentration and temperature. Small-angle scattering indicated the formation of wormlike micelles. The high-Q range was fitted using the Kratky−Porod wormlike chain model, and a cross-sectional radius of gyration (R g,xs) of 21 Å was obtained. Additionally, cryo-TEM images revealed changes in the structure of the entangled network with the addition of salt.