The adsorption of poly(ethylene oxide) (PEO) on synthetic anisotropic clay particles (Laponite) has been investigated as a function of the molecular weight. Contrast variation small-angle neutron scattering (SANS) measurements were used to characterize the distribution and adsorbed amount of polymer on the particles. These experiments show not only that polymer is present on the face of the clay particle but that it also extends or "wraps" over the edges. The edge layer was thicker than the face layer for all the molecular weights studied. The polymer layers are unusually thin, with a thickness and adsorbed amount that show little variation with molecular weight.
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.
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