Vesicle to Micelle Transition:  Rheological Investigations

Abstract

Rheological experiments were carried out on aqueous dispersions of cetyltrimethylammoniumhydroxynaphthalenecarboxylate (CTAHNC) as a function of temperature. The results indicate the formation of very long elongated wormlike micelles at temperatures higher than about 50 °C, conferring to the system a very high viscosity. This behavior is explained by the combined effect of a large end cap energy and a low ionization degree resulting from a strong binding of the weakly soluble counterions. At lower temperature the surfactant forms a much more fluid vesicle phase, which is observed by videomicroscopy. Experiments performed on mixtures of CTAHNC and of cetyltrimethylammonium bromide (CTAB) show also a vesicle to micelle transition for a ratio of CTAB/CTAHNC that decreases upon increasing the temperature. The rheological behavior of the micellar phase obtained by mixing CTAB and CTAHNC is similar to that obtained for other charged micellar solutions.

Rheological characterizations of wormlike micellar solutions containing cationic surfactant and anionic hydrotropic salt

“…Notably, the rich phase behavior of CTAB/SHNC mixture is similar to that of the mixture of cationic-anionic surfactant system [CTAB/Sodium dodecyl sulfate (SDS)] as described by Kaler et al (1989). SHNC is thus considered as an anionic surfactant similar to SDS but with a shorter hydrophobic tail (around 4 nm) ; Hassan et al (1996); Horbaschek et al (1998)]. …”

“…Mixing ionic surfactants with inorganic or organic salts, such as sodium chloride (NaCl), sodium salicylate (NaSal), or 3-hydroxy-naphthalene-2-carboxylate (SHNC), the electrostatic repulsion between the charged head groups is screened by oppositely charged counterions. This can consequently change the micelle packing parameters in the surfactant system, with the formation of rodlike micelles becoming more energetically favorable [Abdel-Rahem (2008); Brackman and Engberts (1991); Hassan et al (1996), Israelachvili (1985); Kim and Yang (2000); Oelschlaeger et al (2010Oelschlaeger et al ( , 2003; Ohlendorf (1986)]. Hydrotropic salts are a class of amphiphilic compounds that cannot form micellar aggregates, but can solubilize organic molecules in water.…”

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

“…1 The addition of inorganic salts to ionic surfactant solutions screens the repulsions between the charged heads and decreases the concentration at which the transition from spherical to rod-like micelles occurs. [2][3][4][5][6][7] This transition takes place at even lower concentrations in the presence of organic (hydrotropic) salts or in surfactants with counterions such as salicylate, 3,[8][9][10] tosylate, 11 chlorobenzoate, 12 hydroxyl naphthalene carboxylate, 5,13 and alkyl sulfates 14 without the addition of electrolytes. The intensity of binding to the micelles is a function of the hydrophobicity of the counterion.…”

“…8,13,[43][44][45] Also, _ g c1 and _ g c2 appear to be related to the crossover frequencies of G 0 and G 00 in the low and high frequency regions, i.e., to the inverses of the reptation (long relaxation) and Rouse times. Mcleish and Ball, 45 based on the Doi-Edwards reptation theory for polymer solutions, proposed that these characteristic times provide two conditions in the s-_ g relationship that give rise to shear banding flow.…”

Heat‐Induced Phase Transitions from an Aqueous Solution to Precipitates in a Poly(sodium 4‐styrenesulfonate)/Tetradecyltrimethylammonium Bromide System

“…Temperature has a large effect on block copolymers, such as triblock copolymers of type (EO) x (PO) y (EO) x , or nonionic surfactant solutions. Traditionally, at higher temperatures, aggregates with larger aggregation numbers could transform into primary aggregates, such as the transition from vesicles to micelles, [5][6][7] that is, the aggregate size normally becomes smaller as the temperature increases. The reverse process, going from small selfassembled aggregates to larger ones, has rarely been reported.…”