Phase equilibria of the mixed didodecyldimethylammonium bromide-sodium taurodeoxycholate-water system with a large solution region

• Type: Article in International Scientific Journal
• Date: 2005

Authors

Sjobom, MB (Author) Other; Marques, EF (Author) FCUP; Edlund, H (Author) Other; Khan, A (Author) Other

Journal

Title: Colloids and Surfaces A: Physicochemical and Engineering Aspects

Vol. 269

Pages: 87-95

ISSN: 0927-7757

Publisher: Elsevier

Indexing

ISI Web of Knowledge - 10 Citations

Scopus - 10 Citations

Scientific classification

FOS: Natural sciences > Chemical sciences

Other information

Authenticus ID: P-000-0KV

DOI: 10.1016/j.colsurfa.2005.06.066

Abstract (EN): The phase behavior over the entire concentration range for the system didodecyldimethylammonium bromide (DDAB)-sodium taurodeoxycholate (STDC)-water, at 25 degrees C, has been investigated, with emphasis on the DDAB-rich part. Polarizing microscopy, SAXS, H-2 NMR and H-1 self-diffusion NMR have been used in combination as probing techniques for phase behavior and microstructure. The system forms four major phases, all deriving from the respective binary surfactant systems. The two lamellar phases originating from the binary DDAB-water axis (D-I and D-II, at 3-30 and 83-91 wt.% DDAB, respectively) are only able to incorporate small amounts of STDC. The D-II phase solubilizes a comparatively higher amount of bile salt (up to ca. 6 wt.%), while the D, phase takes up less than 0.25 wt.%. From the STDC-water axis, a solution phase and a "hexagonal-like" liquid crystalline phase are derived, at 0-26 and 37-60 wt.% of STDC, respectively. Heterogeneous regions are also indicated on the basis of NMR and SAXS data. The most striking feature is the large extension of the isotropic solution phase, which originates from the water corner and curves toward the DDAB-rich side of the phase diagram. Even though at the upper limit of the solution phase the amount of water is reduced to 10 wt.%, the measured water and DDAB self-diffusion coefficients exclude the possibility of reverse-type structures.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 9