MEASUREMENT OF DEPLETION INTERACTION IN SEMIDILUTE SOLUTIONS OF WORM-LIKE SURFACTANT AGGREGATES

Citation
P. Kekicheff et al., MEASUREMENT OF DEPLETION INTERACTION IN SEMIDILUTE SOLUTIONS OF WORM-LIKE SURFACTANT AGGREGATES, Journal de physique. II, 4(5), 1994, pp. 735-741
Citations number
26
Categorie Soggetti
Physics, Atomic, Molecular & Chemical",Mechanics
Journal title
ISSN journal
11554312
Volume
4
Issue
5
Year of publication
1994
Pages
735 - 741
Database
ISI
SICI code
1155-4312(1994)4:5<735:MODIIS>2.0.ZU;2-K
Abstract
The force as a function of separation is measured beween two mica surf aces coated with adsorbed bilayers of cetyltrimethylammonium bromide ( CTAB) and immersed in aqueous solutions of elongated and semi-flexible micelles of CTAB. For the range of concentrations studied, where the ionic strength is kept constant, the worm-like micelles form a transie nt network similar to an entangled polymer solution (semi-dilute regim e). The electrical double-layer repulsion between the adsorbed bilayer s is preceded at larger separations by an attraction with two distinct regimes. The first one is the strongest and is attributed to a comple te depletion of micelles. As predicted by the theory, the range of the interaction is reduced while the strength is increased as the volume fraction is increased. The second regime appears at larger separations where an oscillation-like shape is superimposed on a weak attractive background. It is suggested that the attraction results from an orient ation depletion of the anisotropic micelles aligning along the surface s. The oscillatory behavior is further evidenced with measurement of t he structure factor by SANS.