Pure and mixed aqueous micellar solutions of Sodium Dodecyl sulfate (SDS) and Dimethyldodecyl Amine Oxide (DDAO): Role of temperature and composition
Author(s)
Type
Journal Article
Abstract
Aqueous mixtures of anionic and nonionic/cationic surfactants can form non-trivial self-assemblies in solution and exhibit macroscopic responses. Here, we investigate the micellar phase of pure and mixed aqueous solutions of Sodium Dodecyl Sulfate (SDS) and Dimethyldodecyl Amine Oxide (DDAO) using a combination of Small Angle Neutron Scattering (SANS), Fourier-Transform Infrared Spectroscopy (FTIR) and rheological measurements. We examine the effect of temperature (0–60 °C), on the 20 wt% SDS micellar solutions with varying DDAO (5 wt%), and seek to correlate micellar structure with zero-shear solution viscosity. SANS establishes the formation of prolate ellipsoidal micelles in aqueous solutions of pure SDS, DDAO and SDS/DDAO mixtures, whose axial ratio is found to increase upon cooling. Elongation of the ellipsoidal micelles of pure SDS is also induced by the introduction of the non-anionic DDAO, which effectively reduces the repulsive interactions between the anionic SDS head-groups. In FTIR measurements, the formation of elongated mixed ellipsoidal micelles is confirmed by the increase of ordering in the hydrocarbon chain tails and interaction between surfactant head-groups. We find that the zero-shear viscosity of the mixed surfactant solutions increases exponentially with decreasing temperature and increasing DDAO content. Significantly, a master curve for solution viscosity can be obtained in terms of micellar aspect ratio, subsuming the effects of both temperature and DDAO composition in the experimental range investigated. The intrinsic viscosity of mixed micellar solutions is significantly larger than the analytical and numerical predictions for Brownian suspensions of ellipsoidal colloids, highlighting the need to consider interactions of soft micelles under shear, especially at high concentrations.
Date Issued
2021-01-15
Date Acceptance
2020-08-02
Citation
Journal of Colloid and Interface Science, 2021, 582, pp.1116-1127
ISSN
0021-9797
Publisher
Elsevier
Start Page
1116
End Page
1127
Journal / Book Title
Journal of Colloid and Interface Science
Volume
582
Copyright Statement
© 2020 Elsevier Inc. All rights reserved
Identifier
http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000591565300003&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=1ba7043ffcc86c417c072aa74d649202
Subjects
Science & Technology
Physical Sciences
Chemistry, Physical
Chemistry
Temperature
Phase behaviour
Mixed surfactant
Dimethyldodecyl Amine Oxide DDAO
Sodium Dodecyl sulfate SDS
Viscosity
ATR-FTIR
Anionic surfactant
Ellipsoidal micelles
SANS
ANGLE NEUTRON-SCATTERING
DODECYLDIMETHYLAMINE OXIDE
RHEOLOGICAL PROPERTIES
NONIONIC SURFACTANTS
ANIONIC SURFACTANTS
MIXTURES
SHAPE
SULFONATE
Publication Status
Published