Magnetite Nanoparticle-Induced Reinforcement and Thermal Stabilization of Wormlike Micellar Networks

Magnetite (Fe3O4) nanoparticle-based formulations are known to have significant applications in various subsurface processes. However, their tendency to aggregate limits their practical utility. This study demonstrates an effective strategy to stabilize and functionally enhance magnetite nanoparticles in a matrix of viscoelastic wormlike micelles formed by cetyltrimethylammonium bromide (CTAB) and sodium salicylate (NaSal). This work systematically investigates the interaction between like-charged Fe3O4 nanoparticles and wormlike micelles over a practically relevant temperature and concentration range using rheology and cryogenic transmission electron microscopy. The results show that a small nanoparticle loading significantly strengthens the micellar network, causing a pronounced increase in zero-shear viscosity, plateau modulus, and relaxation time. Notably, the optimized system retains strong viscoelastic character up to higher temperatures compared to the base micellar solution without nanoparticles. The system also undergoes time–temperature–concentration superposition, and the corresponding linear viscoelastic analysis suggests a dominant single-relaxation-time Maxwellian behavior. Interestingly, direct imaging confirms the formation of nanoparticle–micelle junctions, wherein nanoparticles act as transient cross-linking points that promote micellar elongation and entanglement. These findings establish a clear structure–property relationship that governs nanoparticle–micelle interactions. The resulting fluids combine enhanced thermal stability, tunable rheology, and magnetic responsiveness, which make them promising candidates for applications such as enhanced oil recovery, drag reduction, and controllable transport in porous media.