Investigations on a detergent system with rodlike micelles

Abstract

Conductivity, kinetic, static and dynamic light scattering, electric birefringence and rheological measurements were carried out on aqueous solutions of Tetradecylpyridinium-n-Heptanesulfonate (C14PyCTSO3) up to high concentrations. In dilute solutions between the critical micelle concentration (cmc) and another characteristic concentration (ct) spherical micelles were detected whose radii were independent of detergent concentration and equal to the length of a detergent molecule ; the aggregation number n of these micelles of about 100 monomers per micelle was also in agreement with the existence of normal spherical micelles of a C~4-detergent. Above the concentration c~ the spherical micelles were found to grow to rodlike aggregates whose short axis was still independent of concentration and equal to the length of a monomer, while the lengths L of the rods increased with increasing detergent concentration. When the lengths L of the rods became comparable with the mean distance a between them, the starting interaction between the rods slowed down their growth. In this concentration range of overlapping rods, the data could be evaluated with a recently developed theory by Doi and Edwards for stiff rods. The rods reached finally a maximum length of about 500 • and decreased again in size upon further increase of concentration when the overlap ratio L/a reached a value of about 1,5.

Laser Light Scattering Evidence for a Common Wormlike Growth Structure of Mixed Micelles in Bile Salt− and Straight-Chain Detergent−Phosphatidylcholine Aqueous Systems: Relevance to the Micellar Structure of Bile

“…This is because the effective value of c* can itself decrease with dilution due to increasing micellar size. We also note that over the past two decades, a number of other micellar solutions have also been found to exhibit the properties of dilute and semidilute solutions of linear polymers (65,(77)(78)(79)(80)(81).…”

Effect of ionic strength on rheological behavior of polymer-like cetyltrimethylammonium tosylate micellar solutions

“…8,[15][16][17][18][19] Some authors have added another inorganic salt, such as NaCl or KBr, to further screen the electrostatic interactions in these surfactant/salt (inorganic or organic)/water micellar systems. 16,[20][21][22] By contrast, the structural and rheological reports on salt-free viscoelastic micellar solutions are scarce. Kern et al 22 investigated the linear viscoelastic behavior of salt-free polymer-like a Departamento de Ingenier ıa Qu ımica, Universidad de Guadalajara, Boul.…”

Pharmaceutical applications for catanionic mixtures

“…Furthermore, the size and shape of the micelles formed can be affected by the salt screening the repulsion between charged headgroups (Mazer et al 1976;Hoffmann et al 1982;Khatory et al 1993;Hassan et al 2002;Raghavan et al 2002b). Moreover, the addition of salt has an impact on catanionic aggregates, for example Brasher et al (1995) showed how an increased amount of sodium bromide caused a micelle to vesicle phase shift in a mixture of CTAB and SOS.…”