A rheological study in the dilute regime of the worm-micelle fluid made of zwitterionic surfactant (TDPS), anionic surfactant (SDS), and brine

Characterization of dynamics and internal structure of a mixed-surfactant wormlike micellar system using NMR and rheometry

“…The proton longitudinal relaxation time T 1 (Fig. 2) can be fit to a mono-exponential decay, with a significant decrease as one crosses the overlap concentration (reported to be at 7 mM by Lopez-Diaz et al 40 ). The change in T 1 indicates a change in the local environment for the surfactant molecules, which corresponds well with the wormlike micelle overlap concentration.…”

“…The TDPS-SDS system was studied at a range of TDPS concentrations C z , spanning both dilute and semidilute regimes at different surfactant ratios R ¼ [SDS]/[TDPS] and different temperatures. 33,40,41 The average micelle contour length was found to be in the micron range and (for R ¼ 0.55) to increase with C z when the wormlike micelles are totally screened by salt addition, while the ''mesh size'' reflecting intermicellar correlations is in the 50-100 nm regime and insensitive to changes in C z , surfactant concentration ratio or temperature. 33 An interesting feature of this system is that while R ¼ 0.55 mixtures could be fitted to Maxwellian viscoelastic behavior with a single relaxation time for the stress relaxation modulus G(t) at long times, 41 those for R ¼ 0.43-0.45 show deviations from the Maxwellian model.…”

“…Allowing for the surface-associated water to diffuse like the surfactant diffusion modifies this result slightly to h/d ¼ 0.186 AE 0.004. Given a micellar diameter of d z 6 nm, 40 this implies a water layer thickness of z3 to 4 monolayers.…”

Dynamic and static radiation scattering in a microemulsion as a function of dispersed phase concentration

“…Hence, some similarities between polymer and worm-like micelle solutions have been observed: e.g., a dependence of intrinsic viscosity/dynamic light scattering parameters on worm-like micelle dimensions [22][23][24], and a rheological behavior that, depending on experimental conditions (e.g. shear rate and temperature), may be shear-thickening or -thinning [25,26]. Several methods have been used to characterize the occurrence of wormlike structures (some of them in microemulsion-based systems [27]): e.g., the transition between nanodrop to wormlike geometries has been characterized using rheological measurements [28][29][30][31] and static scattering techniques [32][33][34].…”

Synergism between anionic double tail and zwitterionic single tail surfactants in the formation of mixed micelles and vesicles, and use of the micelle templates for the synthesis of nano-structured gold particles

“…The combined presence of both cationic and anionic centres in their heads (contrast to the oppositely charged surfactant pairs) makes their attraction forces weak. Although, reports of the mixed zwitterionc and anionic surfactant micelles and their structural transitions prevail in the literature [29][30][31][32][33][34][35][36][37][38][39], micelle to the vesicle conversion of the mixtures of the zwitterionic and the ionic surfactant systems has been only limitedly addressed [37,40,41]. Systematic and planned researches for a better revelation of the phenomenon in the ionic-zwitterionic systems are thus wanted.…”