A SANS investigation of micelles in mixtures of cetyltrimethylammonium bromide (CTAB)/octyl-β-d-glucopyranoside (C8G1) in water/glycerol solvent

Mixtures of a classical cationic surfactant (CTAB) with the sugar surfactant octyl-β-d-glucopyranoside (C8G1) have been studied with respect to their aggregation behaviour in aqueous solution as well as in D2O mixtures with glycerol by means of small-angle neutron scattering (SANS). It is observed that the mixtures are governed by weak synergetic interactions and always form mixed micelles that grow with increasing content of CTAB in the mixtures. For the case of the mixed glycerol/water solvent, the size of the mixed micelles decreases with increasing content of glycerol, thereby also changing the shape from prolate to spherical micelles. The observations can be quantitatively interpreted by the expected variation of the head group area of the cationic surfactant that becomes larger due to the decreasing dielectric constant of the solvent with increasing glycerol content.