Viscoelastic micellar water/CTAB/NaNO₃ solutions: Rheology, SANS and cryo-TEM analysis

TY - JOUR

T1 - Viscoelastic micellar water/CTAB/NaNO3 solutions

T2 - Rheology, SANS and cryo-TEM analysis

AU - Kuperkar, K.

AU - Abezgauz, L.

AU - Danino, D.

AU - Verma, G.

AU - Hassan, P. A.

AU - Aswal, V. K.

AU - Varade, D.

AU - Bahadur, P.

N1 - Funding Information: P.B. thanks CSIR New Delhi, India for financial support.

PY - 2008/7/15

Y1 - 2008/7/15

N2 - Aqueous micellar solutions of the cationic surfactant hexadecyltrimethylammonium bromide (CTAB) and sodium nitrate (NaNO3) were examined using steady and dynamic rheology, small-angle neutron scattering (SANS) and cryogenic-transmission electron microscopy (cryo-TEM). Upon addition of NaNO3, the CTAB spherical micelles transform into long, flexible wormlike micelles, conveying viscoelastic properties to the solutions. The zero-shear viscosity (η0) versus NaNO3 concentration curve exhibits a well-defined maximum. Likewise, upon increase in temperature, the viscosity decreases. Dynamic rheological data of the entangled micellar solutions can be well described by the Maxwell model. Changes in the structural parameters of the micelles with addition of NaNO3 were inferred from SANS measurements. The intensity of scattered neutrons at the low q region was found to increase with increasing NaNO3 concentration. This suggests an increase in size of the micelles and/or decrease of intermicellar interactions with increasing salt concentration. Analysis of the SANS data using prolate ellipsoidal structure and Yukawa form of interaction potential between micelles indicates that addition of NaNO3 leads to a decrease in the surface charge of the ellipsoidal micelles and consequently an increase in their length. The structural transition from spherical to entangled threadlike micelles, induced by the addition of NaNO3 to CTAB micelles is further confirmed by cryo-TEM.

AB - Aqueous micellar solutions of the cationic surfactant hexadecyltrimethylammonium bromide (CTAB) and sodium nitrate (NaNO3) were examined using steady and dynamic rheology, small-angle neutron scattering (SANS) and cryogenic-transmission electron microscopy (cryo-TEM). Upon addition of NaNO3, the CTAB spherical micelles transform into long, flexible wormlike micelles, conveying viscoelastic properties to the solutions. The zero-shear viscosity (η0) versus NaNO3 concentration curve exhibits a well-defined maximum. Likewise, upon increase in temperature, the viscosity decreases. Dynamic rheological data of the entangled micellar solutions can be well described by the Maxwell model. Changes in the structural parameters of the micelles with addition of NaNO3 were inferred from SANS measurements. The intensity of scattered neutrons at the low q region was found to increase with increasing NaNO3 concentration. This suggests an increase in size of the micelles and/or decrease of intermicellar interactions with increasing salt concentration. Analysis of the SANS data using prolate ellipsoidal structure and Yukawa form of interaction potential between micelles indicates that addition of NaNO3 leads to a decrease in the surface charge of the ellipsoidal micelles and consequently an increase in their length. The structural transition from spherical to entangled threadlike micelles, induced by the addition of NaNO3 to CTAB micelles is further confirmed by cryo-TEM.

KW - Cryo-TEM

KW - SANS

KW - Viscoelasticity

KW - Wormlike micelles

UR - http://www.scopus.com/inward/record.url?scp=44649138681&partnerID=8YFLogxK

U2 - 10.1016/j.jcis.2008.04.040

DO - 10.1016/j.jcis.2008.04.040

M3 - 文章

C2 - 18486141

AN - SCOPUS:44649138681

SN - 0021-9797

VL - 323

SP - 403

EP - 409

JO - Journal of Colloid and Interface Science

JF - Journal of Colloid and Interface Science

IS - 2

ER -