Effect of salt on the lamellar L_α-to-MLV transformation in SDS/octanol/water under microfluidic flow

Abstract

We investigate the effect of added (NaCl) salt and varying flow rate on the phase behaviour and flow response of a model surfactant Lα phase, sodium dodecyl sulfate (SDS)/octanol/water, using...

Microfluidic in-line dynamic light scattering with a commercial fibre optic system

“…Finally, we demonstrate the use of the flow-DLS system in the rapid characterisation of a model micellar surfactant solution with addition of salt, namely SDS/NaCl/water, where R H is obtained over time as the composition changes, within 5 s intervals. Owing to its remote fibre-optic configuration, our flow-DLS can be readily integrated within a lab-on-a-chip system, our coupled in a modular fashion with other techniques such as SANS, 46–50 SAXS, 51,52 Raman spectroscopy, 53 microrheology, 54 viscometry, 38 and many other experimental approaches to complement the spatio-temporal characterisation of complex, reactive or dynamic systems.…”

Composition and temperature effects on the solution structure of SDS/octanol/brine by SANS, NMR and microscopy

“…The phase behaviour and rheology of the L a pseudoquaternary SDS/octanol/brine system has been previously investigated, in particular due to its response to flow near the L a -L 3 phase boundary. 17,18,[21][22][23][24][25][26][27][28] In particular, the 6.5% SDS/7.9% octanol/85.6% brine system has been reported to undergo flow-induced phase transformations from lamellar L a to multilamellar vesicles (MLVs), and ordered MLV arrays of prescribed dimensions at selected temperatures (near ambient) and shear rates. Generally, the addition of NaCl promotes the formation of L 4 -L a -L 3 sequence of phases.…”

“…Freyssingeas et al 43 observed an increase in both in d and membrane bending rigidity k in binary C 12 E 5 /water system, rationalised in terms of a decrease in polar headgroup area. While the addition of NaCl to charged surfactants has been shown to decrease the membrane bending rigidity via membrane screening effect at ambient conditions due to charge screening effect, 18,44,45 the increase in temperature will facilitate the dissociation of Na + ions from the SDS in lamellar membrane in presence of brine matrix leading to increase in headgroup repulsions and increase in membrane bending rigidity k. 46 Further, as the Bjerrum length l B increases with temperature, the spatial extent of Coulombic interactions comparatively increases, contributing to an increase in k (see Fig. S5, ESI †), 47…”