Shear and cooling effects on lamellar gel network structure: Insights from Rheo-SANS

We investigate the formation of lamellar gel networks (LGNs) composed of long-chain fatty alcohols (C16, C18) and their mixture, combined with the surfactant cetyltrimethylammonium chloride (CTAC). The study aims to understand how fatty alcohol chain length and preparation processes affect the structural and mechanical properties of LGNs. Using small-angle neutron scattering (SANS) and in-situ rheology, we track the effects of mixing and cooling rates on formulations in aqueous solution. Additional insights into the nanostructure are provided by small- and wide-angle X-ray scattering (SAXS/WAXS), while microscopy and rheology shed light on macroscopic behavior. Results show that all formulations form lamellar structures, with C16/C18 mixtures exhibiting properties intermediate to those of pure C16 and C18 systems. While C16 and C16/C18 exhibit hexagonal lateral packing, C18 leads to an orthorhombic structure. Faster cooling rates favor the formation of multilamellar vesicles and promote system homogeneity. A patchy organization of the surfactant within the fatty alcohol bilayers is also observed. These findings enhance our understanding of the role of long-chain fatty alcohols in LGN formation and their behavior during mixing and cooling.