Spectral and scattering microstructural investigation in cationic gemini surfactants (12-s-12) induced by p-toluidine

Aqueous micellar solutions of cationic gemini surfactants belonging to 12-s-12 series (where s = 4, 5, 6) in presence of p-toluidine (PTD) exhibit a noticeable micellar growth/transition from viscometric and scattering studies. The dynamic light scattering (DLS) and small angle neutron scattering (SANS) showed pronounced micelle growth around pH 5–6 for gemini with varying spacer. The possible reason is attributed in terms of adsorption, surface charge density, chemical environment and orientation of PTD molecules in the micelle. The probable location of PTD in micelle is successfully correlated by the significant positive crosspeaks obtained from two-dimensional nuclear Overhauser effect spectroscopy (2D-NOESY).

pH dependence shape transition in gemini-PTD micellar system (here the concentration of PTD is 100 mM).Figure optionsDownload as PowerPoint slideHighlights
► Gemini surfactants show remarkable increase in viscosity with added p-toluidine.
► Scattering studies show concentration, temperature and pH induced micellar growth.
► The micellar growth was more for surfactant with short spacer.
► The location of p-toluidine in micelles examined by 2D-NOESY is pH dependant.