Light scattering study of a lower critical consolute point in a micellar system

Abstract

2014 Nous avons étudié les solutions micellaires aqueuses de sulfate de dodécyle et de sodium, butanol et chlorure de sodium. En raison de l'écrantage des forces électrostatiques répulsives par les nuages ioniques et de l'existence de forces attractives entre les micelles (éventuellement reliées à l'hydratation), des points critiques inférieurs de démixtion peuvent être trouvés dans ces mélanges. Nos mesures par diffusion de lumière, de volume et de surface, sont en parfait accord avec les théories du groupe de renormalisation pour les phénomènes critiques. De plus, la région critique apparaît plus large que prévue par les modèles d'Ising décorés utilisés pour décrire les points critiques inférieurs.Abstract 2014 We have studied aqueous micellar solutions of sodium dodecyl sulfate, butanol and sodium chloride. Due to the screening of electrostatic repulsive forces by the ionic atmosphere and to the existence of attractive forces (possibly related to hydration) between the micelles, lower critical consolute points can be found in these mixtures. Our data from surface and bulk light scattering are in perfect agreement with the renormalization group theories for critical phenomena. Moreover, the critical region happens to be wider than that predicted by the decorated Ising models used to describe lower critical consolute points.

Near-critical dynamical behavior of an ionic micellar solution

“…[40][41][42][43] Even if the sample concentration is the same as our experiment, Abillon reported that this mixture has ϭ0.62. 17 But their value of exponent was evaluated over the temperature range of ϳ10 Ϫ3 Ͻ(T C ϪT)/T C Ͻ8.0ϫ10 Ϫ3 . Another point to be issued is that T C determined in the present work ͑light scattering experiments͒ is about 12°C less than the reported value by them.…”

“…Such an effect should be enhanced for microemulsions and elongated micelles more. 9,16 In the present work we adopted this model to the anionic surfactant solution of sodium dodecyl sulfate ͑SDS͒ ϩbutanolϩsodium chloride, which has been investigated earlier by Abillon et al 17 They investigated the critical behavior for the same composition as the present work. They obtained the critical exponent as 0.62, in agreement with 3D Ising model prediction, although the system is a multicomponent one.…”

“…This component ratio is same as that reported in Abillon's paper. 17 Light scattering experiments ͑SLS and DLS͒ were carried out by multi-tau photon correlator, BI9000AT supplied by Brooke Haven Corporation. Our experimental procedures are essentially similar to those described in the previous paper.…”

Bulk and interfacial properties of a cationic micellar system near the critical point

“…Previous studies have also reported disagreements with the universal value predicted by theory for Eq. (20) [21,23].…”

“…Even though these relationships are a strong test about universality classes, not much is known for complex structured systems because the determination of the critical amplitudes can only be done after careful analysis of extremely precise data. This is probably the reason why some contradictory results can be found in the literature [20][21][22][23].…”