Effect of substitution on aniline in inducing growth of anionic micelles

GUNJAN GARG¹, V K ASWAL², S K KULSHRESHTHA¹ and P A HASSAN^1,*

¹Novel Materials and Structural Chemistry Division; ²Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400 085, India

*Corresponding author

E-mail: hassan@apsara.barc.ernet.in

Abstract. Small-angle neutron scattering (SANS) measurements were carried out on sodium dodecyl sulfate (SDS) micelles in the presence of three different hydrophobic salts, i.e. aniline hydrochloride, o-toluidine hydrochloride and $m$-toluidine hydrochloride. All these salts induce a uniaxial growth of micelles to form prolate ellipsoidal structures. A progressive decrease in the surface charge of the micelles was observed with the addition of salts followed by a rapid growth of the micelles. The presence of a methyl substitution at the ortho position of aniline does not alter the growth behavior significantly. However, when the substitution is at meta position micellar growth is favored at lower salt concentration than that is observed for aniline. This can be explained in terms of the difference in the chemical environments of the substituents at the ortho and meta positions.

Keywords. Small-angle neutron scattering; micelle; hydrophobic salts.

PACS Nos 61.12.Ex; 82.70.Uv; 87.64.Lg