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Effects of Shear on the Structures in a System of Small Rodlike Micelles

Published online by Cambridge University Press:  22 February 2011

Paul D. Butler ,
L.J. Magid ,
William A. Hamilton ,
P.J. Kreke  and
Johnb. Hayter
Paul D. Butler
Affiliation:
Department of Chemistry, University of Tennessee, Knoxville, TN 37996
L.J. Magid
Affiliation:
Department of Chemistry, University of Tennessee, Knoxville, TN 37996
William A. Hamilton
Affiliation:
Solid State Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831
P.J. Kreke
Affiliation:
Department of Chemistry, University of Tennessee, Knoxville, TN 37996
Johnb. Hayter
Affiliation:
Solid State Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831
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Abstract

We have used small angle neutron scattering (SANS) to study solutions of cetyltrimethylammonium 2,6-dichlorobenzoate (2,6) at rest and as a function of shear. These solutions are Newtonian, and up to a concentration of at least 100mM contain spherical micelles. Comparison with viscoelastic solutions of the closely related, and much studied, cetyltrimethylammonium 3,5-dichlorobenzoate (3,5) is made. While spheres are not expected to align under shear, a shear induced sphere to rod transition has been postulated for this system. In the results presented here, no shear induced sphere to rod transition was observed even at the highest accessible shear rate. Addition of sufficient supporting electrolyte (up to 1M NaCl) does cause such a transition in the quiescent solution. Hoffmann et al. have seen what they refer to as the formation of a shear induced structure (SIS or type II micelles) on similar systems where short rods form in the absence of supporting electrolyte. Shearing of the salted system produces rapid though not spectacular alignment, with no evidence of a SIS forming.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 376: Symposium BB – Neutron Scattering in Materials Science , 1994 , 313
Copyright
Copyright © Materials Research Society 1995

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References

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