Structural Transition of Oil-Swollen Cylindrical Micelles of C12E5 in Water Studied by SANS

• Published in: The journal of physical chemistry. B Vol. 107; no. 6; pp. 1316 - 1320
• Main Authors: Menge, U, Lang, P, Findenegg, G. H, Strunz, P
• Format: Journal Article
• Language: English
• Published: American Chemical Society 13-02-2003
• ISSN: 1520-6106; 1520-5207
• DOI: 10.1021/jp021797e

The effect of added oil on the local structure of oil-swollen cylindrical micelles in the system C12E5 + decane + water was investigated by small-angle neutron scattering (SANS). The geometry of the aggregates was studied for fixed overall concentration of surfactant plus oil, c m = 7 mg/mL, and increasing oil content α (the mass fraction of oil in the dispersed mixture of surfactant plus oil), to clarify the dependency of the apparent molar mass on α which was observed in a preceding light scattering study (J. Phys. Chem. B 1999, 103, 5768). There it was found that with increasing α at given c m the molar mass of the micelles increases up to a maximum near α = 0.07 and then decreases sharply as the oil content is further increased. The present work shows that this decrease of the molar mass results from a decrease of the micellar contour length L c, whereas the mass per unit length M L of the aggregates increases almost linearly over the entire range of oil content.